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• Problem with increment in inline ARM assembly

  - by tech74

  Hi , i have the following bit of inline ARM assembly, it works in a debug build but crashes in a release build of iphone sdk 3.1. The problem is the add instructions where i am incrementing the address of the C variables output and x by 4 bytes, this is supposed to increment by the size of a float. I think when i increment at some such stage i am overwriting something, can anyone say which is the best way to handle this Thanks C code that the asm is replacing, sum,output and x are all floats for(int i = 0; i< count; i++) sum+= output[i]* (*x++) asm volatile( ".align 4 \n\t" "mov r4,%3 \n\t" "flds s0,[%0] \n\t" "0: \n\t" "flds s1,[%2] \n\t" //"add %3,%3,#4 \n\t" "flds s2,[%1] \n\t" //"add %2,%2,#4 \n\t" "subs r4,r4, #1 \n\t" "fmacs s0, s1, s2 \n\t" "bne 0b \n\t" "fsts s0,[%0] \n\t" : : "r" (&sum), "r" (output), "r" (x),"r" (count) : "r0","r4","cc", "memory", "s0","s1","s2" );

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• pointers in C with a #define

  - by milan

  The function: #define ASSOC(port) (*(volatile bit_field *) (&port)) The function call: #define SCLK ASSOC(PORTC).bit0 bit_field defined as a struct like this: typedef struct { unsigned char bit0 :1, bit1 :1, bit2 :1, bit3 :1, bit4 :1, bit5 :1, bit6 :1, bit7 :1; } bit_field; I don't know where &port is defined. Can someone please explain how the function is read and how it works please? I am not very good with pointers and this example in particular is very confusing with "*" in the front and at the end and the "&" with the port. Thank you

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• Using locks inside a loop

  - by Xaqron

  // Member Variable private readonly object _syncLock = new object(); // Now inside a static method foreach (var lazyObject in plugins) { if ((string)lazyObject.Metadata["key"] = "something") { lock (_syncLock) { if (!lazyObject.IsValueCreated) lazyObject.value.DoSomething(); } return lazyObject.value; } } Here I need synchronized access per loop. There are many threads iterating this loop and based on the key they are looking for, a lazy instance is created and returned. lazyObject should not be created more that one time. Although Lazy class is for doing so and despite of the used lock, under high threading I have more than one instance created (I track this with a Interlocked.Increment on a volatile shared int and log it somewhere). The problem is I don't have access to definition of Lazy and MEF defines how the Lazy class create objects. My questions: 1) Why the lock doesn't work ? 2) Should I use an array of locks instead of one lock for performance improvement ?

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• Preprocessor not skipping asm directives

  - by demula

  I'm programming to a microprocessor (Coldfire) and I don't have access every day to the microprocessor trainer so I want to be able to execute some of my code on the computer. So I'm trying to skip a part of my code when executing on the computer by defining _TEST_. It doesn't work. It tries to compile the asm code and dies whining about not knowing the registers names (they're defined alright compiling against the Coldfire, not my Intel Core Duo). Any ideas why it's not working? or maybe an alternative way to run the code on the pc without commenting it out?. Here's sample code from my project: inline void ct_sistem_exit(int status) { #ifdef _TEST_ exit(status); #else asm volatile( "moveb #0,%%d1\n\t" "movel #0, %%d0\n\t" "trap #15\n\t" : : : "d0", "d1" ); #endif /* _TEST_ */ } If it helps: using gcc3 with cygwin on Netbeans 6.8

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• memcpy() safety on adjacent memory regions

  - by JaredC

  I recently asked a question on using volatile and was directed to read some very informative articles from Intel and others discussing memory barriers and their uses. After reading these articles I have become quite paranoid though. I have a 64-bit machine. Is it safe to memcpy into adjacent, non-overlapping regions of memory from multiple threads? For example, say I have a buffer: char buff[10]; Is it always safe for one thread to memcpy into the first 5 bytes while a second thread copies into the last 5 bytes? My gut reaction (and some simple tests) indicate that this is completely safe, but I have been unable to find documentation anywhere that can completely convince me.

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• Guidance: A Branching strategy for Scrum Teams

  - by Martin Hinshelwood

  Having a good branching strategy will save your bacon, or at least your code. Be careful when deviating from your branching strategy because if you do, you may be worse off than when you started! This is one possible branching strategy for Scrum teams and I will not be going in depth with Scrum but you can find out more about Scrum by reading the Scrum Guide and you can even assess your Scrum knowledge by having a go at the Scrum Open Assessment. You can also read SSW’s Rules to Better Scrum using TFS which have been developed during our own Scrum implementations. Acknowledgements Bill Heys – Bill offered some good feedback on this post and helped soften the language. Note: Bill is a VS ALM Ranger and co-wrote the Branching Guidance for TFS 2010 Willy-Peter Schaub – Willy-Peter is an ex Visual Studio ALM MVP turned blue badge and has been involved in most of the guidance including the Branching Guidance for TFS 2010 Chris Birmele – Chris wrote some of the early TFS Branching and Merging Guidance. Dr Paul Neumeyer, Ph.D Parallel Processes, ScrumMaster and SSW Solution Architect – Paul wanted to have feature branches coming from the release branch as well. We agreed that this is really a spin-off that needs own project, backlog, budget and Team. Scenario: A product is developed RTM 1.0 is released and gets great sales.  Extra features are demanded but the new version will have double to price to pay to recover costs, work is approved by the guys with budget and a few sprints later RTM 2.0 is released.  Sales a very low due to the pricing strategy. There are lots of clients on RTM 1.0 calling out for patches. As I keep getting Reverse Integration and Forward Integration mixed up and Bill keeps slapping my wrists I thought I should have a reminder: You still seemed to use reverse and/or forward integration in the wrong context. I would recommend reviewing your document at the end to ensure that it agrees with the common understanding of these terms merge (forward integration) from parent to child (same direction as the branch), and merge  (reverse integration) from child to parent (the reverse direction of the branch). - one of my many slaps on the wrist from Bill Heys.   As I mentioned previously we are using a single feature branching strategy in our current project. The single biggest mistake developers make is developing against the “Main” or “Trunk” line. This ultimately leads to messy code as things are added and never finished. Your only alternative is to NEVER check in unless your code is 100%, but this does not work in practice, even with a single developer. Your ADD will kick in and your half-finished code will be finished enough to pass the build and the tests. You do use builds don’t you? Sadly, this is a very common scenario and I have had people argue that branching merely adds complexity. Then again I have seen the other side of the universe ... branching  structures from he... We should somehow convince everyone that there is a happy between no-branching and too-much-branching. - Willy-Peter Schaub, VS ALM Ranger, Microsoft   A key benefit of branching for development is to isolate changes from the stable Main branch. Branching adds sanity more than it adds complexity. We do try to stress in our guidance that it is important to justify a branch, by doing a cost benefit analysis. The primary cost is the effort to do merges and resolve conflicts. A key benefit is that you have a stable code base in Main and accept changes into Main only after they pass quality gates, etc. - Bill Heys, VS ALM Ranger & TFS Branching Lead, Microsoft The second biggest mistake developers make is branching anything other than the WHOLE “Main” line. If you branch parts of your code and not others it gets out of sync and can make integration a nightmare. You should have your Source, Assets, Build scripts deployment scripts and dependencies inside the “Main” folder and branch the whole thing. Some departments within MSFT even go as far as to add the environments used to develop the product in there as well; although I would not recommend that unless you have a massive SQL cluster to house your source code. We tried the “add environment” back in South-Africa and while it was “phenomenal”, especially when having to switch between environments, the disk storage and processing requirements killed us. We opted for virtualization to skin this cat of keeping a ready-to-go environment handy. - Willy-Peter Schaub, VS ALM Ranger, Microsoft   I think people often think that you should have separate branches for separate environments (e.g. Dev, Test, Integration Test, QA, etc.). I prefer to think of deploying to environments (such as from Main to QA) rather than branching for QA). - Bill Heys, VS ALM Ranger & TFS Branching Lead, Microsoft   You can read about SSW’s Rules to better Source Control for some additional information on what Source Control to use and how to use it. There are also a number of branching Anti-Patterns that should be avoided at all costs: You know you are on the wrong track if you experience one or more of the following symptoms in your development environment: Merge Paranoia—avoiding merging at all cost, usually because of a fear of the consequences. Merge Mania—spending too much time merging software assets instead of developing them. Big Bang Merge—deferring branch merging to the end of the development effort and attempting to merge all branches simultaneously. Never-Ending Merge—continuous merging activity because there is always more to merge. Wrong-Way Merge—merging a software asset version with an earlier version. Branch Mania—creating many branches for no apparent reason. Cascading Branches—branching but never merging back to the main line. Mysterious Branches—branching for no apparent reason. Temporary Branches—branching for changing reasons, so the branch becomes a permanent temporary workspace. Volatile Branches—branching with unstable software assets shared by other branches or merged into another branch. Note   Branches are volatile most of the time while they exist as independent branches. That is the point of having them. The difference is that you should not share or merge branches while they are in an unstable state. Development Freeze—stopping all development activities while branching, merging, and building new base lines. Berlin Wall—using branches to divide the development team members, instead of dividing the work they are performing. -Branching and Merging Primer by Chris Birmele - Developer Tools Technical Specialist at Microsoft Pty Ltd in Australia   In fact, this can result in a merge exercise no-one wants to be involved in, merging hundreds of thousands of change sets and trying to get a consolidated build. Again, we need to find a happy medium. - Willy-Peter Schaub on Merge Paranoia Merge conflicts are generally the result of making changes to the same file in both the target and source branch. If you create merge conflicts, you will eventually need to resolve them. Often the resolution is manual. Merging more frequently allows you to resolve these conflicts close to when they happen, making the resolution clearer. Waiting weeks or months to resolve them, the Big Bang approach, means you are more likely to resolve conflicts incorrectly. - Bill Heys, VS ALM Ranger & TFS Branching Lead, Microsoft   Figure: Main line, this is where your stable code lives and where any build has known entities, always passes and has a happy test that passes as well? Many development projects consist of, a single “Main” line of source and artifacts. This is good; at least there is source control . There are however a couple of issues that need to be considered. What happens if: you and your team are working on a new set of features and the customer wants a change to his current version? you are working on two features and the customer decides to abandon one of them? you have two teams working on different feature sets and their changes start interfering with each other? I just use labels instead of branches? That's a lot of “what if’s”, but there is a simple way of preventing this. Branching… In TFS, labels are not immutable. This does not mean they are not useful. But labels do not provide a very good development isolation mechanism. Branching allows separate code sets to evolve separately (e.g. Current with hotfixes, and vNext with new development). I don’t see how labels work here. - Bill Heys, VS ALM Ranger & TFS Branching Lead, Microsoft   Figure: Creating a single feature branch means you can isolate the development work on that branch.   Its standard practice for large projects with lots of developers to use Feature branching and you can check the Branching Guidance for the latest recommendations from the Visual Studio ALM Rangers for other methods. In the diagram above you can see my recommendation for branching when using Scrum development with TFS 2010. It consists of a single Sprint branch to contain all the changes for the current sprint. The main branch has the permissions changes so contributors to the project can only Branch and Merge with “Main”. This will prevent accidental check-ins or checkouts of the “Main” line that would contaminate the code. The developers continue to develop on sprint one until the completion of the sprint. Note: In the real world, starting a new Greenfield project, this process starts at Sprint 2 as at the start of Sprint 1 you would have artifacts in version control and no need for isolation.   Figure: Once the sprint is complete the Sprint 1 code can then be merged back into the Main line. There are always good practices to follow, and one is to always do a Forward Integration from Main into Sprint 1 before you do a Reverse Integration from Sprint 1 back into Main. In this case it may seem superfluous, but this builds good muscle memory into your developer’s work ethic and means that no bad habits are learned that would interfere with additional Scrum Teams being added to the Product. The process of completing your sprint development: The Team completes their work according to their definition of done. Merge from “Main” into “Sprint1” (Forward Integration) Stabilize your code with any changes coming from other Scrum Teams working on the same product. If you have one Scrum Team this should be quick, but there may have been bug fixes in the Release branches. (we will talk about release branches later) Merge from “Sprint1” into “Main” to commit your changes. (Reverse Integration) Check-in Delete the Sprint1 branch Note: The Sprint 1 branch is no longer required as its useful life has been concluded. Check-in Done But you are not yet done with the Sprint. The goal in Scrum is to have a “potentially shippable product” at the end of every Sprint, and we do not have that yet, we only have finished code.   Figure: With Sprint 1 merged you can create a Release branch and run your final packaging and testing In 99% of all projects I have been involved in or watched, a “shippable product” only happens towards the end of the overall lifecycle, especially when sprints are short. The in-between releases are great demonstration releases, but not shippable. Perhaps it comes from my 80’s brain washing that we only ship when we reach the agreed quality and business feature bar. - Willy-Peter Schaub, VS ALM Ranger, Microsoft Although you should have been testing and packaging your code all the way through your Sprint 1 development, preferably using an automated process, you still need to test and package with stable unchanging code. This is where you do what at SSW we call a “Test Please”. This is first an internal test of the product to make sure it meets the needs of the customer and you generally use a resource external to your Team. Then a “Test Please” is conducted with the Product Owner to make sure he is happy with the output. You can read about how to conduct a Test Please on our Rules to Successful Projects: Do you conduct an internal "test please" prior to releasing a version to a client?   Figure: If you find a deviation from the expected result you fix it on the Release branch. If during your final testing or your “Test Please” you find there are issues or bugs then you should fix them on the release branch. If you can’t fix them within the time box of your Sprint, then you will need to create a Bug and put it onto the backlog for prioritization by the Product owner. Make sure you leave plenty of time between your merge from the development branch to find and fix any problems that are uncovered. This process is commonly called Stabilization and should always be conducted once you have completed all of your User Stories and integrated all of your branches. Even once you have stabilized and released, you should not delete the release branch as you would with the Sprint branch. It has a usefulness for servicing that may extend well beyond the limited life you expect of it. Note: Don't get forced by the business into adding features into a Release branch instead that indicates the unspoken requirement is that they are asking for a product spin-off. In this case you can create a new Team Project and branch from the required Release branch to create a new Main branch for that product. And you create a whole new backlog to work from.   Figure: When the Team decides it is happy with the product you can create a RTM branch. Once you have fixed all the bugs you can, and added any you can’t to the Product Backlog, and you Team is happy with the result you can create a Release. This would consist of doing the final Build and Packaging it up ready for your Sprint Review meeting. You would then create a read-only branch that represents the code you “shipped”. This is really an Audit trail branch that is optional, but is good practice. You could use a Label, but Labels are not Auditable and if a dispute was raised by the customer you can produce a verifiable version of the source code for an independent party to check. Rare I know, but you do not want to be at the wrong end of a legal battle. Like the Release branch the RTM branch should never be deleted, or only deleted according to your companies legal policy, which in the UK is usually 7 years.   Figure: If you have made any changes in the Release you will need to merge back up to Main in order to finalise the changes. Nothing is really ever done until it is in Main. The same rules apply when merging any fixes in the Release branch back into Main and you should do a reverse merge before a forward merge, again for the muscle memory more than necessity at this stage. Your Sprint is now nearly complete, and you can have a Sprint Review meeting knowing that you have made every effort and taken every precaution to protect your customer’s investment. Note: In order to really achieve protection for both you and your client you would add Automated Builds, Automated Tests, Automated Acceptance tests, Acceptance test tracking, Unit Tests, Load tests, Web test and all the other good engineering practices that help produce reliable software.     Figure: After the Sprint Planning meeting the process begins again. Where the Sprint Review and Retrospective meetings mark the end of the Sprint, the Sprint Planning meeting marks the beginning. After you have completed your Sprint Planning and you know what you are trying to achieve in Sprint 2 you can create your new Branch to develop in. How do we handle a bug(s) in production that can’t wait? Although in Scrum the only work done should be on the backlog there should be a little buffer added to the Sprint Planning for contingencies. One of these contingencies is a bug in the current release that can’t wait for the Sprint to finish. But how do you handle that? Willy-Peter Schaub asked an excellent question on the release activities: In reality Sprint 2 starts when sprint 1 ends + weekend. Should we not cater for a possible parallelism between Sprint 2 and the release activities of sprint 1? It would introduce FI’s from main to sprint 2, I guess. Your “Figure: Merging print 2 back into Main.” covers, what I tend to believe to be reality in most cases. - Willy-Peter Schaub, VS ALM Ranger, Microsoft I agree, and if you have a single Scrum team then your resources are limited. The Scrum Team is responsible for packaging and release, so at least one run at stabilization, package and release should be included in the Sprint time box. If more are needed on the current production release during the Sprint 2 time box then resource needs to be pulled from Sprint 2. The Product Owner and the Team have four choices (in order of disruption/cost): Backlog: Add the bug to the backlog and fix it in the next Sprint Buffer Time: Use any buffer time included in the current Sprint to fix the bug quickly Make time: Remove a Story from the current Sprint that is of equal value to the time lost fixing the bug(s) and releasing. Note: The Team must agree that it can still meet the Sprint Goal. Cancel Sprint: Cancel the sprint and concentrate all resource on fixing the bug(s) Note: This can be a very costly if the current sprint has already had a lot of work completed as it will be lost. The choice will depend on the complexity and severity of the bug(s) and both the Product Owner and the Team need to agree. In this case we will go with option #2 or #3 as they are uncomplicated but severe bugs. Figure: Real world issue where a bug needs fixed in the current release. If the bug(s) is urgent enough then then your only option is to fix it in place. You can edit the release branch to find and fix the bug, hopefully creating a test so it can’t happen again. Follow the prior process and conduct an internal and customer “Test Please” before releasing. You can read about how to conduct a Test Please on our Rules to Successful Projects: Do you conduct an internal "test please" prior to releasing a version to a client?   Figure: After you have fixed the bug you need to ship again. You then need to again create an RTM branch to hold the version of the code you released in escrow.   Figure: Main is now out of sync with your Release. We now need to get these new changes back up into the Main branch. Do a reverse and then forward merge again to get the new code into Main. But what about the branch, are developers not working on Sprint 2? Does Sprint 2 now have changes that are not in Main and Main now have changes that are not in Sprint 2? Well, yes… and this is part of the hit you take doing branching. But would this scenario even have been possible without branching?   Figure: Getting the changes in Main into Sprint 2 is very important. The Team now needs to do a Forward Integration merge into their Sprint and resolve any conflicts that occur. Maybe the bug has already been fixed in Sprint 2, maybe the bug no longer exists! This needs to be identified and resolved by the developers before they continue to get further out of Sync with Main. Note: Avoid the “Big bang merge” at all costs.   Figure: Merging Sprint 2 back into Main, the Forward Integration, and R0 terminates. Sprint 2 now merges (Reverse Integration) back into Main following the procedures we have already established.   Figure: The logical conclusion. This then allows the creation of the next release. By now you should be getting the big picture and hopefully you learned something useful from this post. I know I have enjoyed writing it as I find these exploratory posts coupled with real world experience really help harden my understanding.  Branching is a tool; it is not a silver bullet. Don’t over use it, and avoid “Anti-Patterns” where possible. Although the diagram above looks complicated I hope showing you how it is formed simplifies it as much as possible.   Technorati Tags: Branching,Scrum,VS ALM,TFS 2010,VS2010

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• Mac OS X roaming profile from Samba with OpenLDAP backend on Ubuntu 11.10

  - by Sam Hammamy

  I have been battling for a week now to get my Mac (Mountain Lion) to authenticate on my home network's OpenLDAP and Samba. From several sources, like the Ubuntu community docs, and other blogs, and after a hell of a lot of trial and error and piecing things together, I have created a samba.ldif that will pass the smbldap-populate when combined with apple.ldif and I have a fully functional OpenLDAP server and a Samba PDC that uses LDAP to authenticate the OS X Machine. The problem is that when I login, the home directory is not created or pulled from the server. I get the following in system.log Sep 21 06:09:15 Sams-MacBook-Pro.local SecurityAgent[265]: User info context values set for sam Sep 21 06:09:15 Sams-MacBook-Pro.local authorizationhost[270]: in pam_sm_authenticate(): Got user: sam Sep 21 06:09:15 Sams-MacBook-Pro.local authorizationhost[270]: in pam_sm_authenticate(): Got ruser: (null) Sep 21 06:09:15 Sams-MacBook-Pro.local authorizationhost[270]: in pam_sm_authenticate(): Got service: authorization Sep 21 06:09:15 Sams-MacBook-Pro.local authorizationhost[270]: in od_principal_for_user(): no authauth availale for user. Sep 21 06:09:15 Sams-MacBook-Pro.local authorizationhost[270]: in od_principal_for_user(): failed: 7 Sep 21 06:09:15 Sams-MacBook-Pro.local authorizationhost[270]: in pam_sm_authenticate(): Failed to determine Kerberos principal name. Sep 21 06:09:15 Sams-MacBook-Pro.local authorizationhost[270]: in pam_sm_authenticate(): Done cleanup3 Sep 21 06:09:15 Sams-MacBook-Pro.local authorizationhost[270]: in pam_sm_authenticate(): Kerberos 5 refuses you Sep 21 06:09:15 Sams-MacBook-Pro.local authorizationhost[270]: in pam_sm_authenticate(): pam_sm_authenticate: ntlm Sep 21 06:09:15 Sams-MacBook-Pro.local authorizationhost[270]: in pam_sm_acct_mgmt(): OpenDirectory - Membership cache TTL set to 1800. Sep 21 06:09:15 Sams-MacBook-Pro.local authorizationhost[270]: in od_record_check_pwpolicy(): retval: 0 Sep 21 06:09:15 Sams-MacBook-Pro.local authorizationhost[270]: in pam_sm_setcred(): Establishing credentials Sep 21 06:09:15 Sams-MacBook-Pro.local authorizationhost[270]: in pam_sm_setcred(): Got user: sam Sep 21 06:09:15 Sams-MacBook-Pro.local authorizationhost[270]: in pam_sm_setcred(): Context initialised Sep 21 06:09:15 Sams-MacBook-Pro.local authorizationhost[270]: in pam_sm_setcred(): pam_sm_setcred: ntlm user sam doesn't have auth authority All that's great and good and I authenticate. Then I get CFPreferences: user home directory for user kCFPreferencesCurrentUser at /Network/Servers/172.17.148.186/home/sam is unavailable. User domains will be volatile. Failed looking up user domain root; url='file://localhost/Network/Servers/172.17.148.186/home/sam/' path=/Network/Servers/172.17.148.186/home/sam/ err=-43 uid=9000 euid=9000 If you're wondering where /Network/Servers/IP/home/sam comes from, it's from a couple of blogs that said the OpenLDAP attribute apple-user-homeDirectory should have that value and the NFSHomeDirectory on the mac should point to apple-user-homeDirectory I also set the attr apple-user-homeurl to <home_dir><url>smb://172.17.148.186/sam/</url><path></path></home_dir> which I found on this forum. Any help is appreciated, because I'm banging my head against the wall at this point. By the way, I intend to create a blog on my vps just for this, and create an install script in python that people can download so no one has to go through what I've had to go through this week :) After some sleep I am going to try to login from a windows machine and report back here. Thanks Sam

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• PTLQueue : a scalable bounded-capacity MPMC queue

  - by Dave

  Title: Fast concurrent MPMC queue -- I've used the following concurrent queue algorithm enough that it warrants a blog entry. I'll sketch out the design of a fast and scalable multiple-producer multiple-consumer (MPSC) concurrent queue called PTLQueue. The queue has bounded capacity and is implemented via a circular array. Bounded capacity can be a useful property if there's a mismatch between producer rates and consumer rates where an unbounded queue might otherwise result in excessive memory consumption by virtue of the container nodes that -- in some queue implementations -- are used to hold values. A bounded-capacity queue can provide flow control between components. Beware, however, that bounded collections can also result in resource deadlock if abused. The put() and take() operators are partial and wait for the collection to become non-full or non-empty, respectively. Put() and take() do not allocate memory, and are not vulnerable to the ABA pathologies. The PTLQueue algorithm can be implemented equally well in C/C++ and Java. Partial operators are often more convenient than total methods. In many use cases if the preconditions aren't met, there's nothing else useful the thread can do, so it may as well wait via a partial method. An exception is in the case of work-stealing queues where a thief might scan a set of queues from which it could potentially steal. Total methods return ASAP with a success-failure indication. (It's tempting to describe a queue or API as blocking or non-blocking instead of partial or total, but non-blocking is already an overloaded concurrency term. Perhaps waiting/non-waiting or patient/impatient might be better terms). It's also trivial to construct partial operators by busy-waiting via total operators, but such constructs may be less efficient than an operator explicitly and intentionally designed to wait. A PTLQueue instance contains an array of slots, where each slot has volatile Turn and MailBox fields. The array has power-of-two length allowing mod/div operations to be replaced by masking. We assume sensible padding and alignment to reduce the impact of false sharing. (On x86 I recommend 128-byte alignment and padding because of the adjacent-sector prefetch facility). Each queue also has PutCursor and TakeCursor cursor variables, each of which should be sequestered as the sole occupant of a cache line or sector. You can opt to use 64-bit integers if concerned about wrap-around aliasing in the cursor variables. Put(null) is considered illegal, but the caller or implementation can easily check for and convert null to a distinguished non-null proxy value if null happens to be a value you'd like to pass. Take() will accordingly convert the proxy value back to null. An advantage of PTLQueue is that you can use atomic fetch-and-increment for the partial methods. We initialize each slot at index I with (Turn=I, MailBox=null). Both cursors are initially 0. All shared variables are considered "volatile" and atomics such as CAS and AtomicFetchAndIncrement are presumed to have bidirectional fence semantics. Finally T is the templated type. I've sketched out a total tryTake() method below that allows the caller to poll the queue. tryPut() has an analogous construction. Zebra stripping : alternating row colors for nice-looking code listings. See also google code "prettify" : https://code.google.com/p/google-code-prettify/ Prettify is a javascript module that yields the HTML/CSS/JS equivalent of pretty-print. -- pre:nth-child(odd) { background-color:#ff0000; } pre:nth-child(even) { background-color:#0000ff; } border-left: 11px solid #ccc; margin: 1.7em 0 1.7em 0.3em; background-color:#BFB; font-size:12px; line-height:65%; " // PTLQueue : Put(v) : // producer : partial method - waits as necessary assert v != null assert Mask = 1 && (Mask & (Mask+1)) == 0 // Document invariants // doorway step // Obtain a sequence number -- ticket // As a practical concern the ticket value is temporally unique // The ticket also identifies and selects a slot auto tkt = AtomicFetchIncrement (&PutCursor, 1) slot * s = &Slots[tkt & Mask] // waiting phase : // wait for slot's generation to match the tkt value assigned to this put() invocation. // The "generation" is implicitly encoded as the upper bits in the cursor // above those used to specify the index : tkt div (Mask+1) // The generation serves as an epoch number to identify a cohort of threads // accessing disjoint slots while s-Turn != tkt : Pause assert s-MailBox == null s-MailBox = v // deposit and pass message Take() : // consumer : partial method - waits as necessary auto tkt = AtomicFetchIncrement (&TakeCursor,1) slot * s = &Slots[tkt & Mask] // 2-stage waiting : // First wait for turn for our generation // Acquire exclusive "take" access to slot's MailBox field // Then wait for the slot to become occupied while s-Turn != tkt : Pause // Concurrency in this section of code is now reduced to just 1 producer thread // vs 1 consumer thread. // For a given queue and slot, there will be most one Take() operation running // in this section. // Consumer waits for producer to arrive and make slot non-empty // Extract message; clear mailbox; advance Turn indicator // We have an obvious happens-before relation : // Put(m) happens-before corresponding Take() that returns that same "m" for T v = s-MailBox if v != null : s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 // unlock slot to admit next producer and consumer return v Pause tryTake() : // total method - returns ASAP with failure indication for auto tkt = TakeCursor slot * s = &Slots[tkt & Mask] if s-Turn != tkt : return null T v = s-MailBox // presumptive return value if v == null : return null // ratify tkt and v values and commit by advancing cursor if CAS (&TakeCursor, tkt, tkt+1) != tkt : continue s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 return v The basic idea derives from the Partitioned Ticket Lock "PTL" (US20120240126-A1) and the MultiLane Concurrent Bag (US8689237). The latter is essentially a circular ring-buffer where the elements themselves are queues or concurrent collections. You can think of the PTLQueue as a partitioned ticket lock "PTL" augmented to pass values from lock to unlock via the slots. Alternatively, you could conceptualize of PTLQueue as a degenerate MultiLane bag where each slot or "lane" consists of a simple single-word MailBox instead of a general queue. Each lane in PTLQueue also has a private Turn field which acts like the Turn (Grant) variables found in PTL. Turn enforces strict FIFO ordering and restricts concurrency on the slot mailbox field to at most one simultaneous put() and take() operation. PTL uses a single "ticket" variable and per-slot Turn (grant) fields while MultiLane has distinct PutCursor and TakeCursor cursors and abstract per-slot sub-queues. Both PTL and MultiLane advance their cursor and ticket variables with atomic fetch-and-increment. PTLQueue borrows from both PTL and MultiLane and has distinct put and take cursors and per-slot Turn fields. Instead of a per-slot queues, PTLQueue uses a simple single-word MailBox field. PutCursor and TakeCursor act like a pair of ticket locks, conferring "put" and "take" access to a given slot. PutCursor, for instance, assigns an incoming put() request to a slot and serves as a PTL "Ticket" to acquire "put" permission to that slot's MailBox field. To better explain the operation of PTLQueue we deconstruct the operation of put() and take() as follows. Put() first increments PutCursor obtaining a new unique ticket. That ticket value also identifies a slot. Put() next waits for that slot's Turn field to match that ticket value. This is tantamount to using a PTL to acquire "put" permission on the slot's MailBox field. Finally, having obtained exclusive "put" permission on the slot, put() stores the message value into the slot's MailBox. Take() similarly advances TakeCursor, identifying a slot, and then acquires and secures "take" permission on a slot by waiting for Turn. Take() then waits for the slot's MailBox to become non-empty, extracts the message, and clears MailBox. Finally, take() advances the slot's Turn field, which releases both "put" and "take" access to the slot's MailBox. Note the asymmetry : put() acquires "put" access to the slot, but take() releases that lock. At any given time, for a given slot in a PTLQueue, at most one thread has "put" access and at most one thread has "take" access. This restricts concurrency from general MPMC to 1-vs-1. We have 2 ticket locks -- one for put() and one for take() -- each with its own "ticket" variable in the form of the corresponding cursor, but they share a single "Grant" egress variable in the form of the slot's Turn variable. Advancing the PutCursor, for instance, serves two purposes. First, we obtain a unique ticket which identifies a slot. Second, incrementing the cursor is the doorway protocol step to acquire the per-slot mutual exclusion "put" lock. The cursors and operations to increment those cursors serve double-duty : slot-selection and ticket assignment for locking the slot's MailBox field. At any given time a slot MailBox field can be in one of the following states: empty with no pending operations -- neutral state; empty with one or more waiting take() operations pending -- deficit; occupied with no pending operations; occupied with one or more waiting put() operations -- surplus; empty with a pending put() or pending put() and take() operations -- transitional; or occupied with a pending take() or pending put() and take() operations -- transitional. The partial put() and take() operators can be implemented with an atomic fetch-and-increment operation, which may confer a performance advantage over a CAS-based loop. In addition we have independent PutCursor and TakeCursor cursors. Critically, a put() operation modifies PutCursor but does not access the TakeCursor and a take() operation modifies the TakeCursor cursor but does not access the PutCursor. This acts to reduce coherence traffic relative to some other queue designs. It's worth noting that slow threads or obstruction in one slot (or "lane") does not impede or obstruct operations in other slots -- this gives us some degree of obstruction isolation. PTLQueue is not lock-free, however. The implementation above is expressed with polite busy-waiting (Pause) but it's trivial to implement per-slot parking and unparking to deschedule waiting threads. It's also easy to convert the queue to a more general deque by replacing the PutCursor and TakeCursor cursors with Left/Front and Right/Back cursors that can move either direction. Specifically, to push and pop from the "left" side of the deque we would decrement and increment the Left cursor, respectively, and to push and pop from the "right" side of the deque we would increment and decrement the Right cursor, respectively. We used a variation of PTLQueue for message passing in our recent OPODIS 2013 paper. ul { list-style:none; padding-left:0; padding:0; margin:0; margin-left:0; } ul#myTagID { padding: 0px; margin: 0px; list-style:none; margin-left:0;} -- -- There's quite a bit of related literature in this area. I'll call out a few relevant references: Wilson's NYU Courant Institute UltraComputer dissertation from 1988 is classic and the canonical starting point : Operating System Data Structures for Shared-Memory MIMD Machines with Fetch-and-Add. Regarding provenance and priority, I think PTLQueue or queues effectively equivalent to PTLQueue have been independently rediscovered a number of times. See CB-Queue and BNPBV, below, for instance. But Wilson's dissertation anticipates the basic idea and seems to predate all the others. Gottlieb et al : Basic Techniques for the Efficient Coordination of Very Large Numbers of Cooperating Sequential Processors Orozco et al : CB-Queue in Toward high-throughput algorithms on many-core architectures which appeared in TACO 2012. Meneghin et al : BNPVB family in Performance evaluation of inter-thread communication mechanisms on multicore/multithreaded architecture Dmitry Vyukov : bounded MPMC queue (highly recommended) Alex Otenko : US8607249 (highly related). John Mellor-Crummey : Concurrent queues: Practical fetch-and-phi algorithms. Technical Report 229, Department of Computer Science, University of Rochester Thomasson : FIFO Distributed Bakery Algorithm (very similar to PTLQueue). Scott and Scherer : Dual Data Structures I'll propose an optimization left as an exercise for the reader. Say we wanted to reduce memory usage by eliminating inter-slot padding. Such padding is usually "dark" memory and otherwise unused and wasted. But eliminating the padding leaves us at risk of increased false sharing. Furthermore lets say it was usually the case that the PutCursor and TakeCursor were numerically close to each other. (That's true in some use cases). We might still reduce false sharing by incrementing the cursors by some value other than 1 that is not trivially small and is coprime with the number of slots. Alternatively, we might increment the cursor by one and mask as usual, resulting in a logical index. We then use that logical index value to index into a permutation table, yielding an effective index for use in the slot array. The permutation table would be constructed so that nearby logical indices would map to more distant effective indices. (Open question: what should that permutation look like? Possibly some perversion of a Gray code or De Bruijn sequence might be suitable). As an aside, say we need to busy-wait for some condition as follows : "while C == 0 : Pause". Lets say that C is usually non-zero, so we typically don't wait. But when C happens to be 0 we'll have to spin for some period, possibly brief. We can arrange for the code to be more machine-friendly with respect to the branch predictors by transforming the loop into : "if C == 0 : for { Pause; if C != 0 : break; }". Critically, we want to restructure the loop so there's one branch that controls entry and another that controls loop exit. A concern is that your compiler or JIT might be clever enough to transform this back to "while C == 0 : Pause". You can sometimes avoid this by inserting a call to a some type of very cheap "opaque" method that the compiler can't elide or reorder. On Solaris, for instance, you could use :"if C == 0 : { gethrtime(); for { Pause; if C != 0 : break; }}". It's worth noting the obvious duality between locks and queues. If you have strict FIFO lock implementation with local spinning and succession by direct handoff such as MCS or CLH,then you can usually transform that lock into a queue. Hidden commentary and annotations - invisible : * And of course there's a well-known duality between queues and locks, but I'll leave that topic for another blog post. * Compare and contrast : PTLQ vs PTL and MultiLane * Equivalent : Turn; seq; sequence; pos; position; ticket * Put = Lock; Deposit Take = identify and reserve slot; wait; extract & clear; unlock * conceptualize : Distinct PutLock and TakeLock implemented as ticket lock or PTL Distinct arrival cursors but share per-slot "Turn" variable provides exclusive role-based access to slot's mailbox field put() acquires exclusive access to a slot for purposes of "deposit" assigns slot round-robin and then acquires deposit access rights/perms to that slot take() acquires exclusive access to slot for purposes of "withdrawal" assigns slot round-robin and then acquires withdrawal access rights/perms to that slot At any given time, only one thread can have withdrawal access to a slot at any given time, only one thread can have deposit access to a slot Permissible for T1 to have deposit access and T2 to simultaneously have withdrawal access * round-robin for the purposes of; role-based; access mode; access role mailslot; mailbox; allocate/assign/identify slot rights; permission; license; access permission; * PTL/Ticket hybrid Asymmetric usage ; owner oblivious lock-unlock pairing K-exclusion add Grant cursor pass message m from lock to unlock via Slots[] array Cursor performs 2 functions : + PTL ticket + Assigns request to slot in round-robin fashion Deconstruct protocol : explication put() : allocate slot in round-robin fashion acquire PTL for "put" access store message into slot associated with PTL index take() : Acquire PTL for "take" access // doorway step seq = fetchAdd (&Grant, 1) s = &Slots[seq & Mask] // waiting phase while s-Turn != seq : pause Extract : wait for s-mailbox to be full v = s-mailbox s-mailbox = null Release PTL for both "put" and "take" access s-Turn = seq + Mask + 1 * Slot round-robin assignment and lock "doorway" protocol leverage the same cursor and FetchAdd operation on that cursor FetchAdd (&Cursor,1) + round-robin slot assignment and dispersal + PTL/ticket lock "doorway" step waiting phase is via "Turn" field in slot * PTLQueue uses 2 cursors -- put and take. Acquire "put" access to slot via PTL-like lock Acquire "take" access to slot via PTL-like lock 2 locks : put and take -- at most one thread can access slot's mailbox Both locks use same "turn" field Like multilane : 2 cursors : put and take slot is simple 1-capacity mailbox instead of queue Borrow per-slot turn/grant from PTL Provides strict FIFO Lock slot : put-vs-put take-vs-take at most one put accesses slot at any one time at most one put accesses take at any one time reduction to 1-vs-1 instead of N-vs-M concurrency Per slot locks for put/take Release put/take by advancing turn * is instrumental in ... * P-V Semaphore vs lock vs K-exclusion * See also : FastQueues-excerpt.java dice-etc/queue-mpmc-bounded-blocking-circular-xadd/ * PTLQueue is the same as PTLQB - identical * Expedient return; ASAP; prompt; immediately * Lamport's Bakery algorithm : doorway step then waiting phase Threads arriving at doorway obtain a unique ticket number Threads enter in ticket order * In the terminology of Reed and Kanodia a ticket lock corresponds to the busy-wait implementation of a semaphore using an eventcount and a sequencer It can also be thought of as an optimization of Lamport's bakery lock was designed for fault-tolerance rather than performance Instead of spinning on the release counter, processors using a bakery lock repeatedly examine the tickets of their peers --

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• const vs. readonly for a singleton

  - by GlenH7

  First off, I understand there are folk who oppose the use of singletons. I think it's an appropriate use in this case as it's constant state information, but I'm open to differing opinions / solutions. (See The singleton pattern and When should the singleton pattern not be used?) Second, for a broader audience: C++/CLI has a similar keyword to readonly with initonly, so this isn't strictly a C# type question. (Literal field versus constant variable in C++/CLI) Sidenote: A discussion of some of the nuances on using const or readonly. My Question: I have a singleton that anchors together some different data structures. Part of what I expose through that singleton are some lists and other objects, which represent the necessary keys or columns in order to connect the linked data structures. I doubt that anyone would try to change these objects through a different module, but I want to explicitly protect them from that risk. So I'm currently using a "readonly" modifier on those objects*. I'm using readonly instead of const with the lists as I read that using const will embed those items in the referencing assemblies and will therefore trigger a rebuild of those referencing assemblies if / when the list(s) is/are modified. This seems like a tighter coupling than I would want between the modules, but I wonder if I'm obsessing over a moot point. (This is question #2 below) The alternative I see to using "readonly" is to make the variables private and then wrap them with a public get. I'm struggling to see the advantage of this approach as it seems like wrapper code that doesn't provide much additional benefit. (This is question #1 below) It's highly unlikely that we'll change the contents or format of the lists - they're a compilation of things to avoid using magic strings all over the place. Unfortunately, not all the code has converted over to using this singleton's presentation of those strings. Likewise, I don't know that we'd change the containers / classes for the lists. So while I normally argue for the encapsulations advantages a get wrapper provides, I'm just not feeling it in this case. A representative sample of my singleton public sealed class mySingl { private static volatile mySingl sngl; private static object lockObject = new Object(); public readonly Dictionary<string, string> myDict = new Dictionary<string, string>() { {"I", "index"}, {"D", "display"}, }; public enum parms { ABC = 10, DEF = 20, FGH = 30 }; public readonly List<parms> specParms = new List<parms>() { parms.ABC, parms.FGH }; public static mySingl Instance { get { if(sngl == null) { lock(lockObject) { if(sngl == null) sngl = new mySingl(); } } return sngl; } } private mySingl() { doSomething(); } } Questions: Am I taking the most reasonable approach in this case? Should I be worrying about const vs. readonly? is there a better way of providing this information?

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• Move Data into the grid for scalable, predictable response times

  - by JuergenKress

  CloudTran is pleased to introduce the availability of the CloudTran Transaction and Persistence Manager for creating scalable, reliable data services on the Oracle Coherence In-Memory Data Grid (IMDG). Use of IMDG architectures has been key to handling today’s web-scale loads because it eliminates database latency by storing important and frequently access data in memory instead of on disk. The CloudTran product lets developers easily use an IMDG for full ACID-compliant transactions without having to be concerned about the location or spread of data. The system has its own implementation of fast, scalable distributed transactions that does NOT depend on XA protocols but still guarantees all ACID properties. Plus, CloudTran asynchronously replicates data going into the IMDG to back-end datastores and back-up data centers, again ensuring ACID properties. CloudTran can be accessed through Java Persistence API (JPA via TopLink Grid) and now, through a new Low-Level API, or LLAPI. This is ideal for use in SOA applications that need data reliability, high availability, performance, and scalability. It is still in its limited beta release, the LLAPI gives developers the ability to use standard put/remove logic available in Coherence and then wrap logic with simple Spring annotations or XML+AspectJ to start transactions. An important feature of LLAPI is the ability to join transactions. This is a common outcome for SOA applications that need to reduce network traffic by aggregating data into single cache entries and then doing SOA service processing in the node holding the data. This results in the need to orchestrate transaction processing across multiple service calls. CloudTran has the capability to handle these “multi-client” transactions at speed with no loss in ACID properties. Developing software around an IMDG like Oracle Coherence is an important choice for today’s web-scale applications and services. But this introduces new architectural considerations to maintain scalability in light of increased network loads and data movement. Without using CloudTran, developers are faced with an incredibly difficult task to ensure data reliability, availability, performance, and scalability when working with an IMDG. Working with highly distributed data that is entirely volatile while stored in memory presents numerous edge cases where failures can result in data loss. The CloudTran product takes care of all of this, leaving developers with the confidence and peace of mind that all data is processed correctly. For those interested in evaluating the CloudTran product and IMDGs, take a look at this link for more information: http://www.CloudTran.com/downloadAPI.ph , or send your questions to [email protected]. SOA & BPM Partner Community For regular information on Oracle SOA Suite become a member in the SOA & BPM Partner Community for registration please visit  www.oracle.com/goto/emea/soa (OPN account required) If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Technorati Tags: CloudTran,data grid,M,SOA Community,Oracle SOA,Oracle BPM,BPM,Community,OPN,Jürgen Kress

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• Move Data into the Grid for Scalable, Predictable Response Times

  - by JuergenKress

  CloudTran is pleased to introduce the availability of the CloudTran Transaction and Persistence Manager for creating scalable, reliable data services on the Oracle Coherence In-Memory Data Grid (IMDG). Use of IMDG architectures has been key to handling today’s web-scale loads because it eliminates database latency by storing important and frequently access data in memory instead of on disk. The CloudTran product lets developers easily use an IMDG for full ACID-compliant transactions without having to be concerned about the location or spread of data. The system has its own implementation of fast, scalable distributed transactions that does NOT depend on XA protocols but still guarantees all ACID properties. Plus, CloudTran asynchronously replicates data going into the IMDG to back-end datastores and back-up data centers, again ensuring ACID properties. CloudTran can be accessed through Java Persistence API (JPA via TopLink Grid) and now, through a new Low-Level API, or LLAPI. This is ideal for use in SOA applications that need data reliability, high availability, performance, and scalability. Still in limited beta release, the LLAPI gives developers the ability to use standard put/remove logic available in Coherence and then wrap logic with simple Spring annotations or XML+AspectJ to start transactions. An important feature of LLAPI is the ability to join transactions. This is a common outcome for SOA applications that need to reduce network traffic by aggregating data into single cache entries and then doing SOA service processing in the node holding the data. This results in the need to orchestrate transaction processing across multiple service calls. CloudTran has the capability to handle these “multi-client” transactions at speed with no loss in ACID properties. Developing software around an IMDG like Oracle Coherence is an important choice for today’s web-scale applications and services. But this introduces new architectural considerations to maintain scalability in light of increased network loads and data movement. Without using CloudTran, developers are faced with an incredibly difficult task to ensure data reliability, availability, performance, and scalability when working with an IMDG. Working with highly distributed data that is entirely volatile while stored in memory presents numerous edge cases where failures can result in data loss. The CloudTran product takes care of all of this, leaving developers with the confidence and peace of mind that all data is processed correctly. For those interested in evaluating the CloudTran product and IMDGs, take a look at this link for more information: http://www.CloudTran.com/downloadAPI.php, or, send your questions to [email protected]. WebLogic Partner Community For regular information become a member in the WebLogic Partner Community please visit: http://www.oracle.com/partners/goto/wls-emea ( OPN account required). If you need support with your account please contact the Oracle Partner Business Center. BlogTwitterLinkedInMixForumWiki Technorati Tags: Coherence,cloudtran,cache,WebLogic Community,Oracle,OPN,Jürgen Kress

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• StringBuffer behavior in LWJGL

  - by Michael Oberlin

  Okay, I've been programming in Java for about ten years, but am entirely new to LWJGL. I have a specific problem whilst attempting to create a text console. I have built a class meant to abstract input polling to it, which (in theory) captures key presses from the Keyboard object and appends them to a StringBuilder/StringBuffer, then retrieves the completed string after receiving the ENTER key. The problem is, after I trigger the String return (currently with ESCAPE), and attempt to print it to System.out, I consistently get a blank line. I can get an appropriate string length, and I can even sample a single character out of it and get complete accuracy, but it never prints the actual string. I could swear that LWJGL slipped some kind of thread-safety trick in while I wasn't looking. Here's my code: static volatile StringBuffer command = new StringBuffer(); @Override public void chain(InputPoller poller) { this.chain = poller; } @Override public synchronized void poll() { //basic testing for modifier keys, to be used later on boolean shift = false, alt = false, control = false, superkey = false; if(Keyboard.isKeyDown(Keyboard.KEY_LSHIFT) || Keyboard.isKeyDown(Keyboard.KEY_RSHIFT)) shift = true; if(Keyboard.isKeyDown(Keyboard.KEY_LMENU) || Keyboard.isKeyDown(Keyboard.KEY_RMENU)) alt = true; if(Keyboard.isKeyDown(Keyboard.KEY_LCONTROL) || Keyboard.isKeyDown(Keyboard.KEY_RCONTROL)) control = true; if(Keyboard.isKeyDown(Keyboard.KEY_LMETA) || Keyboard.isKeyDown(Keyboard.KEY_RMETA)) superkey = true; while(Keyboard.next()) if(Keyboard.getEventKeyState()) { command.append(Keyboard.getEventCharacter()); } if (Framework.isConsoleEnabled() && Keyboard.isKeyDown(Keyboard.KEY_ESCAPE)) { System.out.println("Escape down"); System.out.println(command.length() + " characters polled"); //works System.out.println(command.toString().length()); //works System.out.println(command.toString().charAt(4)); //works System.out.println(command.toString().toCharArray()); //blank line! System.out.println(command.toString()); //blank line! Framework.disableConsole(); } //TODO: Add command construction and console management after that } } Maybe the answer's obvious and I'm just feeling tired, but I need to walk away from this for a while. If anyone sees the issue, please let me know. This machine is running the latest release of Java 7 on Ubuntu 12.04, Mate desktop environment. Many thanks.

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• SuperMicro BMC on OpenSuSE Linux --cannot access from LAN

  - by Kendall

  Hi, I have an (old) SMC-001 IPMI device on an (old) X6DVL-EG2 motherboard. My problem is that I cannot access the BMC from LAN. I'm also getting some interesting output from ipmitool. First, the setup. I enable Console Redirection in the BIOS, turn BIOS Redirection after POSt to "disabled". I then modprobe'ed for ipmi_msghandler, ipmi_devintf and ipmi_si. I then found ipmi0 under /dev. So far so good. Since I want console redirection over serial, I modified /boot/grub/menu.lst: http://pastebin.com/YYJmhusQ I then modified "/etc/inittab" as follows: S1:12345:respawn:/sbin/agetty -L 19200 ttyS1 ansi Networking I set as following, using "ipmitool" ipaddr: 192.168.3.164 netmask: 255.255.255.0 defgw: 192.168.3.1 The above are correct for my environment. To test it I do: ipmitool -I open chassis power off which responds by powering off the machine. When I to access from another computer on the network, however, I get an error message: host# ipmitool -I lanplus -H 192.168.10.164 -U Admin -a chassis power status Error: Unable to establish LAN session Unable to get Chassis Power Status "Admin" seems to be a valid user name: host# ipmitool -I open user list 1 2 Admin true false true USER The interesting output from ipmitool I initially mentioned: host # ipmitool -I open lan set 1 access on Set Channel Access for channel 1 failed: Request data field length limit exceeded Also, newload4:/home/gjones # ipmitool channel info 1 Channel 0x1 info: Channel Medium Type : 802.3 LAN Channel Protocol Type : IPMB-1.0 Session Support : session-less Active Session Count : 0 Protocol Vendor ID : 7154 Get Channel Access (volatile) failed: Request data field length limit exceeded The output of "ipmitool -I open lan print 1" is here: http://pastebin.com/UZyL6yyE Any help/suggestions is greatly appreciated; I've been working with this thing for a few hours now with no success.

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• cisco 2900xl - SNMP - Get mac address of device connected to an interface

  - by ankit

  Hello all, Basically what i want to do is to find out what is the mac address of a device plugged in to an interface on the switch (FastEthernet0/1 for example) reading through the switch documentaion i found out that i can configure snmp trap on it to make it notify of any new mac address the switch detects by using the command snmp-server enable traps mac-notifiction but for some reason my switch does not support this feature. the only options i see are CORE_SWITCH(config)#snmp-server enable traps ? c2900 Enable SNMP c2900 traps cluster Enable Cluster traps config Enable SNMP config traps entity Enable SNMP entity traps hsrp Enable SNMP HSRP traps snmp Enable SNMP traps vlan-membership Enable VLAN Membership traps vtp Enable SNMP VTP traps <cr> so the other way would be for me to run a cronjon on my gateway to poll the switch periodically using snmp to get new mac addresses i have looked everywhere but cant seem to find the OID that would provide me this information. any help i can get would me very much appreciated ! here's the output from "show version" on my switch Cisco Internetwork Operating System Software IOS (tm) C2900XL Software (C2900XL-C3H2S-M), Version 12.0(5.4)WC(1), MAINTENANCE INTERIM SOFTWARE Copyright (c) 1986-2001 by cisco Systems, Inc. Compiled Tue 10-Jul-01 11:52 by devgoyal Image text-base: 0x00003000, data-base: 0x00333CD8 ROM: Bootstrap program is C2900XL boot loader CORE_SWITCH uptime is 1 hour, 24 minutes System returned to ROM by power-on System image file is "flash:c2900XL-c3h2s-mz.120-5.4.WC.1.bin" cisco WS-C2912-XL (PowerPC403GA) processor (revision 0x11) with 8192K/1024K bytes of memory. Processor board ID FAB0409X1WS, with hardware revision 0x01 Last reset from power-on Processor is running Enterprise Edition Software Cluster command switch capable Cluster member switch capable 12 FastEthernet/IEEE 802.3 interface(s) 32K bytes of flash-simulated non-volatile configuration memory. Base ethernet MAC Address: 00:01:42:D0:67:00 Motherboard assembly number: 73-3397-08 Power supply part number: 34-0834-01 Motherboard serial number: FAB040843G4 Power supply serial number: DAB05030HR8 Model revision number: A0 Motherboard revision number: C0 Model number: WS-C2912-XL-EN System serial number: FAB0409X1WS Configuration register is 0xF thanks, -ankit

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• CentOS 6.3 X86_64 RAM detection

  - by Peter

  I have a machine with 8GB ram (BIOS sees it, so my motherboard and CPU supports it), and I installed CentOS 6.3 on it. When it starts up, it only see 3.1GB. uname says: 2.6.32-279.1.1.el6.x86_64 #1 SMP BIOS-provided physical RAM map: BIOS-e820: 0000000000000000 - 000000000009fc00 (usable) BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved) BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved) BIOS-e820: 0000000000100000 - 00000000cf65f000 (usable) BIOS-e820: 00000000cf65f000 - 00000000cf6e8000 (ACPI NVS) BIOS-e820: 00000000cf6e8000 - 00000000cf6ec000 (usable) BIOS-e820: 00000000cf6ec000 - 00000000cf6ff000 (ACPI data) BIOS-e820: 00000000cf6ff000 - 00000000cf700000 (usable) dmesg | grep -i memory says: initial memory mapped : 0 - 20000000 init_memory_mapping: 0000000000000000-00000000cf700000 Reserving 129MB of memory at 48MB for crashkernel (System RAM: 3319MB) PM: Registered nosave memory: 000000000009f000 - 00000000000a0000 PM: Registered nosave memory: 00000000000a0000 - 00000000000e0000 PM: Registered nosave memory: 00000000000e0000 - 0000000000100000 PM: Registered nosave memory: 00000000cf65f000 - 00000000cf6e8000 PM: Registered nosave memory: 00000000cf6ec000 - 00000000cf6ff000 Memory: 3184828k/3398656k available (5152k kernel code, 1016k absent, 212812k reserved, 7166k data, 1260k init) please try 'cgroup_disable=memory' option if you don't want memory cgroups Initializing cgroup subsys memory Freeing initrd memory: 16136k freed Non-volatile memory driver v1.3 agpgart-intel 0000:00:00.0: detected 8192K stolen memory crash memory driver: version 1.1 Freeing unused kernel memory: 1260k freed Freeing unused kernel memory: 972k freed Freeing unused kernel memory: 1732k freed Update: Memtest see all the 8GB, and dmidecode -t 17 | grep Size too. But free -m still see only 3.1 GB. Question: How can I repair/modify the system, to see all the 8GB RAM? Thanks in advance!

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• Better approach to archiving large amounts of original video footage using optical media (DVD/Blu-ra

  - by Rob

  This question is to share my experience as well as ask for suggestions for better methods. Along with 2 friends, I completed the making of a short documentary film in 2006. Clip is at: http://www.youtube.com/mediamotioninvision The film was edited in Adobe Premiere Pro 1.5 on Windows XP. More details and screenshot here: http://www.flickr.com/photos/smilingrobbie/1350235514/ ( note this is not intended to be a plug, we've moved on from this initial learning curve project ;) ) The film is in 4:3 standard definition 720x576 PAL format. As well as retaining the final 30minute film, I wanted to keep all original files that assembled together to make the film. The footage was 83.5Gb So I archived them to over 20 4.7Gb DVD recordables in the original .avi format (i.e. data DVD-ROM format, NOT DVD-Video Mpeg2) Some .avi DV video files were larger than 4.7Gb so I used 7-zip to split them ( here is a guide as to how to do that: http://www.linglom.com/2008/10/12/how-to-split-a-large-file-using-7-zip/ ) To recombine them, a dos shell command like this would do that: copy /b file.avi.* file.avi would do the job, where .* is a wild card to include all the split parts e.g. 001, 002...00n assuming they are all in the same directory path folder. file.avi is the recombined file identical to the original. Later on, I bought a LG BE06 LU10 USB 2.0 Super-multi Blu-ray burner and archived the footage to 2 (two) x 50Gb BD-R DL discs. Again in the original format, written as files to a BD-R in the BD-R BD-ROM UDF format readable by PC/Mac etc, NOT Blu-ray video/film format. This seems to be a good solution for me, because: the archive is in a robust, reasonably permanent, non-volatile medium, i.e. DVD recordable / Blu-ray (debates about stability of optical media organic chemical dye compounds/substrates aside) the format of the archive is accessible by open source tools or just plain Windows Explorer and it's not in a proprietary format I just thought I'd ask folks for their experience on better methods, if such exist.

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• Cisco Catalyst 4500 Policy Based Routing

  - by Logan

  In order to test a new firewall I just set up I'm trying to implement policy based routing on our core switch. I want traffic from certain vlans to be routed to the new firewall while everything else continues being routed through the old firewall. I was trying to use this guide. Everything from that guide works fine except trying to run the "ip policy route-map" command in the interface configuration mode. IOS is telling me that such a command doesn't exist. A "show ip interface vlan" command says that policy routing is disabled. Any ideas? Output of "show ver": Cisco IOS Software, Catalyst 4500 L3 Switch Software (cat4500-IPBASEK9-M), Version 12.2(53)SG, RELEASE SOFTWARE (fc3) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2009 by Cisco Systems, Inc. Compiled Thu 16-Jul-09 19:49 by prod_rel_team Image text-base: 0x10000000, data-base: 0x11D1E3CC ROM: 12.2(31r)SG2 Dagobah Revision 226, Swamp Revision 34 RTTMCB2223-1 uptime is 3 years, 22 weeks, 2 days, 19 hours, 28 minutes Uptime for this control processor is 51 weeks, 2 days, 18 hours, 2 minutes System returned to ROM by power-on System restarted at 19:22:02 UTC Tue Jul 12 2011 System image file is "bootflash:cat4500-ipbasek9-mz.122-53.sg.bin" ... cisco WS-C4510R (MPC8245) processor (revision 4) with 524288K bytes of memory. Processor board ID FOX103703W3 MPC8245 CPU at 400Mhz, Supervisor V Last reset from PowerUp 42 Virtual Ethernet interfaces 244 Gigabit Ethernet interfaces 511K bytes of non-volatile configuration memory. Configuration register is 0x2

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• Access to File being restricted after Ubuntu crashed

  - by Tim

  My Ubuntu 8.10 crashed due to the overheating problem of the CPU when I am opening some directory and intend to do some file transfer under Nautilus. After reboot, under gnome, all the files cannot be removed, their properties cannot be viewed and they can only be opened, although all are still fine under terminal. I was wondering why is that and how can I fix it? Thanks and regards UPdate $ cat /etc/mtab /dev/sda7 / ext3 rw,relatime,errors=remount-ro 0 0 tmpfs /lib/init/rw tmpfs rw,nosuid,mode=0755 0 0 /proc /proc proc rw,noexec,nosuid,nodev 0 0 sysfs /sys sysfs rw,noexec,nosuid,nodev 0 0 varrun /var/run tmpfs rw,nosuid,mode=0755 0 0 varlock /var/lock tmpfs rw,noexec,nosuid,nodev,mode=1777 0 0 udev /dev tmpfs rw,mode=0755 0 0 tmpfs /dev/shm tmpfs rw,nosuid,nodev 0 0 devpts /dev/pts devpts rw,noexec,nosuid,gid=5,mode=620 0 0 fusectl /sys/fs/fuse/connections fusectl rw 0 0 lrm /lib/modules/2.6.27-15-generic/volatile tmpfs rw,mode=755 0 0 /dev/sda8 /home ext3 rw,relatime 0 0 /dev/sda2 /windows-c vfat rw,utf8,umask=007,gid=46 0 0 /dev/sda5 /windows-d fuseblk rw,allow_other,blksize=4096 0 0 securityfs /sys/kernel/security securityfs rw 0 0 binfmt_misc /proc/sys/fs/binfmt_misc binfmt_misc rw,noexec,nosuid,nodev 0 0 gvfs-fuse-daemon /home/tim/.gvfs fuse.gvfs-fuse-daemon rw,nosuid,nodev,user=tim 0 0

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• How to have a shell script available everywhere I SSH to

  - by aib

  I have a shell script which I simply cannot do without: bar from Theiling Online I use SSH a lot and on a variety of *nix servers. However, I am not a system administrator and usually don't have the time or privileges to install it on every server I connect to. It is apparently a very portable sh script and has command line options to export itself as a shell function, which got me thinking: Could I use one of OpenSSH's subjectively obscure features to export it everywhere I go? My first thought was to assign the source to an environment variable like BAR = "cat -v" and then execute it on the other side as `$BAR`, but 1) I can't even get the cat example to to work locally, 2) I don't know how to put the script's actual multiline source into an environment variable and 3) I have yet to see a machine with PermitUserEnvironment enabled. I guess I could even do with an ssh option to write a file called ~/bar at logon, but a more volatile solution would be better. Calling wget http://.../bar at logon would be unacceptable. Any ideas? P.S. Putty-specific solutions, though I doubt any would exist, are also fine.

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• Backing up a Windos 7 partition from Macbook with no OS X

  - by mattcodes

  I have a 3 year macbook with Windows 7 installed as 40gb and OS X as 40gb (80gb HD). I want to remove OS X as Im at the limit of 40gb on Windows and I have not logged on to Mac OS X since installed Win7 (dont flame me). So I want to delete OS X partition and expand my win partition to 80gb BUT I still would like to be able to regularly (once a week/month) backup my Windows 7 partition - its took a while to setup everything up right - not just docs and programs - so when the hard drive dies I want to be able to restore the partition and boot away, (the daily volatile bits I can pull down from dropbox and project from soure control). With Mac OS X I could use Winclone - and this worked flawless last time the HD failed with XP but with the absence of OS X I will need something else. Im thinking can I use a Linux Live boot CD along with an external USB hard drive. Boot from CD and then dd? the partition to the USB? What linux distro live CD should I use? I say dd as if I know what am taking about (I dont) is this the best way to backup a partition (when it will be restored to same hardware as bootable) ? What command?

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• Large, high performance object or key/value store for HTTP serving on Linux

  - by Tommy

  I have a service that serves images to end users at a very high rate using plain HTTP. The images vary between 4 and 64kbytes, and there are 1.300.000.000 of them in total. The dataset is about 30TiB in size and changes (new objects, updates, deletes) make out less than 1% of the requests. The number of requests pr. second vary from 240 to 9000 and is dispersed pretty much all over, with few objects being especially "hot". As of now, these images are files on a ext3 filesystem distributed read only across a large amount of mid range servers. This poses several problems: Using a fileysystem is very inefficient since the metadata size is large, the inode/dentry cache is volatile on linux and some daemons tend to stat()/readdir() it's way through the directory structure, which in my case becomes very expensive. Updating the dataset is very time consuming and requires remounting between set A and B. The only reasonable handling is operating on the block device for backup, copying, etc. What I would like is a deamon that: speaks HTTP (get, put, delete and perhaps update) stores data it in an efficient structure. The index should remain in memory, and considering the amount of objects, the overhead must be small. The software should be able to handle massive connections with slow (if any) time needed to ramp up. Index should be read in memory at startup. Statistics would be nice, but not mandatory. I have experimented a bit with riak, redis, mongodb, kyoto and varnish with persistent storage, but I haven't had the chance to dig in really deep yet.

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• How do I add a second disk to my zfs root pool

  - by ankimal

  I am trying to add a new disk to my zfs root pool. Here is my current config: zpool status pool: rpool state: ONLINE scrub: none requested config: NAME STATE READ WRITE CKSUM rpool ONLINE 0 0 0 c0d0s0 ONLINE 0 0 0 errors: No known data errors bash-3.00# df -h Filesystem Size Used Avail Use% Mounted on rpool/ROOT/s10x_u7wos_08 311G 18G 293G 6% / swap 14G 384K 14G 1% /etc/svc/volatile /usr/lib/libc/libc_hwcap1.so.1 311G 18G 293G 6% /lib/libc.so.1 swap 14G 52K 14G 1% /tmp swap 14G 40K 14G 1% /var/run rpool/export 293G 19K 293G 1% /export rpool/export/home 430G 138G 293G 32% /export/home rpool 293G 36K 293G 1% /rpool # format Searching for disks...done AVAILABLE DISK SELECTIONS: 0. c0d0 <DEFAULT cyl 60797 alt 2 hd 255 sec 63> /pci@0,0/pci-ide@1f,2/ide@0/cmdk@0,0 1. c2d0 <Hitachi- JK1181YAHL0YK-0001-16777216.> /pci@0,0/pci-ide@1f,5/ide@1/cmdk@0,0 Disk 1 above is the new disk I need to attach to expand my root pool (give /export/home some extra space). If I try to attach my new disk to the pool # zpool attach -f rpool c0d0s0 c2d0s0 cannot attach c2d0s0 to c0d0s0: new device must be a single disk # uname -a SunOS dsol1 5.10 Generic_139556-08 i86pc i386 i86pc Solaris Any ideas?

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• GDI+ crashes when loading PNG from IStream

  - by konforce

  I wrote something to load PNG files from a custom C++ IStream via GDI+. It worked great until I ran it on Vista machines. Crashes every time. When compiled on VS 2008, I found that inserting code into the IStream::AddRef method, such as a cout, made the problem go away. When compiling with VS 2010, it still crashes regardless of that. I stripped the program down to its basics. I copied a FileStream straight from Microsoft's documentation. It can load PNGs when using Bitmap::FromFile. It can load JPEGs, GIFs, and BMPs via FromFile or FromStream. So in short: on Vista, PNG files loaded via Bitmap::FromStream crash. #pragma comment(lib, "gdiplus.lib") #include <iostream> #include <objidl.h> #include <gdiplus.h> class FileStream : public IStream { public: FileStream(HANDLE hFile) { _refcount = 1; _hFile = hFile; } ~FileStream() { if (_hFile != INVALID_HANDLE_VALUE) { ::CloseHandle(_hFile); } } public: HRESULT static OpenFile(LPCWSTR pName, IStream ** ppStream, bool fWrite) { HANDLE hFile = ::CreateFileW(pName, fWrite ? GENERIC_WRITE : GENERIC_READ, FILE_SHARE_READ, NULL, fWrite ? CREATE_ALWAYS : OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL); if (hFile == INVALID_HANDLE_VALUE) return HRESULT_FROM_WIN32(GetLastError()); *ppStream = new FileStream(hFile); if(*ppStream == NULL) CloseHandle(hFile); return S_OK; } virtual HRESULT STDMETHODCALLTYPE QueryInterface(REFIID iid, void ** ppvObject) { if (iid == __uuidof(IUnknown) || iid == __uuidof(IStream) || iid == __uuidof(ISequentialStream)) { *ppvObject = static_cast<IStream*>(this); AddRef(); return S_OK; } else return E_NOINTERFACE; } virtual ULONG STDMETHODCALLTYPE AddRef(void) { return (ULONG)InterlockedIncrement(&_refcount); } virtual ULONG STDMETHODCALLTYPE Release(void) { ULONG res = (ULONG) InterlockedDecrement(&_refcount); if (res == 0) delete this; return res; } // ISequentialStream Interface public: virtual HRESULT STDMETHODCALLTYPE Read(void* pv, ULONG cb, ULONG* pcbRead) { ULONG local_pcbRead; BOOL rc = ReadFile(_hFile, pv, cb, &local_pcbRead, NULL); if (pcbRead) *pcbRead = local_pcbRead; return (rc) ? S_OK : HRESULT_FROM_WIN32(GetLastError()); } virtual HRESULT STDMETHODCALLTYPE Write(void const* pv, ULONG cb, ULONG* pcbWritten) { BOOL rc = WriteFile(_hFile, pv, cb, pcbWritten, NULL); return rc ? S_OK : HRESULT_FROM_WIN32(GetLastError()); } // IStream Interface public: virtual HRESULT STDMETHODCALLTYPE SetSize(ULARGE_INTEGER) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE CopyTo(IStream*, ULARGE_INTEGER, ULARGE_INTEGER*, ULARGE_INTEGER*) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE Commit(DWORD) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE Revert(void) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE LockRegion(ULARGE_INTEGER, ULARGE_INTEGER, DWORD) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE UnlockRegion(ULARGE_INTEGER, ULARGE_INTEGER, DWORD) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE Clone(IStream **) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE Seek(LARGE_INTEGER liDistanceToMove, DWORD dwOrigin, ULARGE_INTEGER* lpNewFilePointer) { DWORD dwMoveMethod; switch(dwOrigin) { case STREAM_SEEK_SET: dwMoveMethod = FILE_BEGIN; break; case STREAM_SEEK_CUR: dwMoveMethod = FILE_CURRENT; break; case STREAM_SEEK_END: dwMoveMethod = FILE_END; break; default: return STG_E_INVALIDFUNCTION; break; } if (SetFilePointerEx(_hFile, liDistanceToMove, (PLARGE_INTEGER) lpNewFilePointer, dwMoveMethod) == 0) return HRESULT_FROM_WIN32(GetLastError()); return S_OK; } virtual HRESULT STDMETHODCALLTYPE Stat(STATSTG* pStatstg, DWORD grfStatFlag) { if (GetFileSizeEx(_hFile, (PLARGE_INTEGER) &pStatstg->cbSize) == 0) return HRESULT_FROM_WIN32(GetLastError()); return S_OK; } private: volatile HANDLE _hFile; volatile LONG _refcount; }; #define USE_STREAM int main() { Gdiplus::GdiplusStartupInput gdiplusStartupInput; ULONG_PTR gdiplusToken; Gdiplus::GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL); Gdiplus::Bitmap *bmp; #ifndef USE_STREAM bmp = Gdiplus::Bitmap::FromFile(L"test.png", false); if (!bmp) { std::cerr << " Unable to open image file." << std::endl; return 1; } #else IStream *s; if (FileStream::OpenFile(L"test.png", &s, false) != S_OK) { std::cerr << "Unable to open image file." << std::endl; return 1; } bmp = Gdiplus::Bitmap::FromStream(s, false); #endif std::cout << "Image is " << bmp->GetWidth() << " by " << bmp->GetHeight() << std::endl; Gdiplus::GdiplusShutdown(gdiplusToken); #ifdef USE_STREAM s->Release(); #endif return 0; } Tracing and debugging, shows that it does make some calls to the IStream class. It crashes inside of lastResult = DllExports::GdipCreateBitmapFromStream(stream, &bitmap); from GdiPlusBitmap.h, which is a static inline wrapper over the flat API. Other than the reference counting, the only IStream methods it calls is stat (for file size), read, and seek. Call stack looks like: ntdll.dll!_DbgBreakPoint@0() + 0x1 bytes ntdll.dll!_RtlpBreakPointHeap@4() + 0x28 bytes ntdll.dll!_RtlpValidateHeapEntry@12() + 0x70a3c bytes ntdll.dll!_RtlDebugFreeHeap@12() + 0x9a bytes ntdll.dll!@RtlpFreeHeap@16() + 0x13cdd bytes ntdll.dll!_RtlFreeHeap@12() + 0x2e49 bytes kernel32.dll!_HeapFree@12() + 0x14 bytes ole32.dll!CRetailMalloc_Free() + 0x1c bytes ole32.dll!_CoTaskMemFree@4() + 0x13 bytes GdiPlus.dll!GpPngDecoder::GetImageInfo() + 0x68 bytes GdiPlus.dll!GpDecodedImage::InternalGetImageInfo() + 0x3c bytes GdiPlus.dll!GpDecodedImage::GetImageInfo() + 0x18 bytes GdiPlus.dll!CopyOnWriteBitmap::CopyOnWriteBitmap() + 0x49 bytes GdiPlus.dll!CopyOnWriteBitmap::Create() + 0x1d bytes GdiPlus.dll!GpBitmap::GpBitmap() + 0x2c bytes I was unable to find anybody else with the same problem, so I assume there's something wrong with my implementation...

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• Unable to apt-get upgrade in ubuntu 11.10

  - by blackhole

  These are the errors shows by different client Update Manager: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 968, in simulate trans.unauthenticated = self._simulate_helper(trans) File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 1092, in _simulate_helper return depends, self._cache.required_download, \ File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 235, in required_download pm.get_archives(fetcher, self._list, self._records) SystemError: E:Method has died unexpectedly!, E:Sub-process returned an error code (100), E:Method /usr/lib/apt/methods/ did not start correctly Synaptic package Manager E: Method has died unexpectedly! E: Sub-process returned an error code (100) E: Method /usr/lib/apt/methods/ did not start correctly E: Unable to lock the download directory Command: sudo apt-get upgrade Reading package lists... Done Building dependency tree Reading state information... Done The following packages will be upgraded: libfreetype6 libfreetype6-dev 2 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. Failed to exec method /usr/lib/apt/methods/ E: Method has died unexpectedly! E: Sub-process returned an error code (100) E: Method /usr/lib/apt/methods/ did not start correctly Can anyone one tell me how to resolve these issues ? I have no volatile packages or anything so i am even posting the preview of my sources.list file. # deb cdrom:[Ubuntu 10.10 _Maverick Meerkat_ - Release i386 (20101007)]/ maverick main restricted # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to # newer versions of the distribution. deb http://in.archive.ubuntu.com/ubuntu/ oneiric main restricted ## Major bug fix updates produced after the final release of the ## distribution. deb http://in.archive.ubuntu.com/ubuntu/ oneiric-updates main restricted ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu ## team. Also, please note that software in universe WILL NOT receive any ## review or updates from the Ubuntu security team. deb http://in.archive.ubuntu.com/ubuntu/ oneiric universe deb http://in.archive.ubuntu.com/ubuntu/ oneiric-updates universe ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu ## team, and may not be under a free licence. Please satisfy yourself as to ## your rights to use the software. Also, please note that software in ## multiverse WILL NOT receive any review or updates from the Ubuntu ## security team. deb http://in.archive.ubuntu.com/ubuntu/ oneiric multiverse deb http://in.archive.ubuntu.com/ubuntu/ oneiric-updates multiverse ## Uncomment the following two lines to add software from the 'backports' ## repository. ## N.B. software from this repository may not have been tested as ## extensively as that contained in the main release, although it includes ## newer versions of some applications which may provide useful features. ## Also, please note that software in backports WILL NOT receive any review ## or updates from the Ubuntu security team. # deb http://in.archive.ubuntu.com/ubuntu/ maverick-backports main restricted universe multiverse # deb-src http://in.archive.ubuntu.com/ubuntu/ maverick-backports main restricted universe multiverse ## Uncomment the following two lines to add software from Canonical's ## 'partner' repository. ## This software is not part of Ubuntu, but is offered by Canonical and the ## respective vendors as a service to Ubuntu users. deb http://archive.canonical.com/ubuntu oneiric partner deb-src http://archive.canonical.com/ubuntu oneiric partner ## This software is not part of Ubuntu, but is offered by third-party ## developers who want to ship their latest software. deb http://extras.ubuntu.com/ubuntu oneiric main deb-src http://extras.ubuntu.com/ubuntu oneiric main deb http://in.archive.ubuntu.com/ubuntu/ oneiric-security main restricted deb http://in.archive.ubuntu.com/ubuntu/ oneiric-security universe deb http://in.archive.ubuntu.com/ubuntu/ oneiric-security multiverse # deb http://archive.canonical.com/ lucid partner Here is the preview of my sources.list file

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• Lies, damned lies, and statistics Part 2

  - by Maria Colgan

  There was huge interest in our OOW session last year on Managing Optimizer Statistics. It seems statistics and the maintenance of them continues to baffle people. In order to help dispel the mysteries surround statistics management we have created a two part white paper series on Optimizer statistics.  Part one of this series was released in November last years and describes in detail, with worked examples, the different concepts of Optimizer statistics. Today we have published part two of the series, which focuses on the best practices for gathering statistics, and examines specific use cases including, the fears that surround histograms and statistics management of volatile tables like Global Temporary Tables. Here is a quick look at the Introduction and the start of the paper. You can find the full paper here. Happy Reading! Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman","serif";} Introduction The Oracle Optimizer examines all of the possible plans for a SQL statement and picks the one with the lowest cost, where cost represents the estimated resource usage for a given plan. In order for the Optimizer to accurately determine the cost for an execution plan it must have information about all of the objects (table and indexes) accessed in the SQL statement as well as information about the system on which the SQL statement will be run. This necessary information is commonly referred to as Optimizer statistics. Understanding and managing Optimizer statistics is key to optimal SQL execution. Knowing when and how to gather statistics in a timely manner is critical to maintaining acceptable performance. This whitepaper is the second of a two part series on Optimizer statistics. The first part of this series, Understanding Optimizer Statistics, focuses on the concepts of statistics and will be referenced several times in this paper as a source of additional information. This paper will discuss in detail, when and how to gather statistics for the most common scenarios seen in an Oracle Database. The topics are · How to gather statistics · When to gather statistics · Improving the efficiency of gathering statistics · When not to gather statistics · Gathering other types of statistics How to gather statistics The preferred method for gathering statistics in Oracle is to use the supplied automatic statistics-gathering job. Automatic statistics gathering job The job collects statistics for all database objects, which are missing statistics or have stale statistics by running an Oracle AutoTask task during a predefined maintenance window. Oracle internally prioritizes the database objects that require statistics, so that those objects, which most need updated statistics, are processed first. The automatic statistics-gathering job uses the DBMS_STATS.GATHER_DATABASE_STATS_JOB_PROC procedure, which uses the same default parameter values as the other DBMS_STATS.GATHER_*_STATS procedures. The defaults are sufficient in most cases. However, it is occasionally necessary to change the default value of one of the statistics gathering parameters, which can be accomplished by using the DBMS_STATS.SET_*_PREF procedures. Parameter values should be changed at the smallest scope possible, ideally on a per-object bases. You can find the full paper here. Happy Reading! +Maria Colgan

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