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  • Strange performance issue with Dell R7610 and LSI 2208 RAID controller

    - by GregC
    Connecting controller to any of the three PCIe x16 slots yield choppy read performance around 750 MB/sec Lowly PCIe x4 slot yields steady 1.2 GB/sec read Given same files, same Windows Server 2008 R2 OS, same RAID6 24-disk Seagate ES.2 3TB array on LSI 9286-8e, same Dell R7610 Precision Workstation with A03 BIOS, same W5000 graphics card (no other cards), same settings etc. I see super-low CPU utilization in both cases. SiSoft Sandra reports x8 at 5GT/sec in x16 slot, and x4 at 5GT/sec in x4 slot, as expected. I'd like to be able to rely on the sheer speed of x16 slots. What gives? What can I try? Any ideas? Please assist Cross-posted from http://en.community.dell.com/support-forums/desktop/f/3514/t/19526990.aspx Follow-up information We did some more performance testing with reading from 8 SSDs, connected directly (without an expander chip). This means that both SAS cables were utilized. We saw nearly double performance, but it varied from run to run: {2.0, 1.8, 1.6, and 1.4 GB/sec were observed, then performance jumped back up to 2.0}. The SSD RAID0 tests were conducted in a x16 PCIe slot, all other variables kept the same. It seems to me that we were getting double the performance of HDD-based RAID6 array. Just for reference: maximum possible read burst speed over single channel of SAS 6Gb/sec is 570 MB/sec due to 8b/10b encoding and protocol limitations (SAS cable provides four such channels).

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  • Looking for application performance tracking software

    - by JavaRocky
    I have multiple java-based applications which produce statistics on how long method calls take. Right now the information is being written into a log file and I analyse performance that way. However with multiple apps and more monitoring requirements this is being becoming a bit overwhelming. I am looking for an application which will collect stats and graph them so I can analyse performance and be aware of performance degradation. I have looked at Solarwinds Application Performance Monitoring, however this polls periodically to gather information. My applications are totally event based and we would like to graph and track this accordingly. I almost started hacking together some scripts to produce Google Charts but surely there are applications which do this already. Suggestions?

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  • Hyper-V performance comparisons vs physical client?

    - by rwmnau
    Are there any comparisons between Hyper-V client machines and their physical equivalent? I've looked around and can find 4000 articles about improving Hyper-V performance, but I can't find any that actually do a side-by-side comparison or give benchmarking numbers. Ideally, I'm interested in a comparison of CPU, memory, disk, and graphics performance between something like the following: Some powerful workstation (with plenty of RAM) with Windows 7 installed on it directly Same exact worksation with Hyper-V Server 2008 R2 (the bare Server role) and a full-screen Windows 7 client machine Virtual Server 2005 had performance that didn't compare at all with actual hardware, but with the advances in CPU and hardware-level virtualization, has performance improved significantly? How obvious would it be to a user of the two above scenarios that one of them was virtualized, and does anybody know of actual benchmarking of this type?

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  • LTO 2 tape performance in LTO 3 drive

    - by hmallett
    I have a pile of LTO 2 tapes, and both an LTO 2 drive (HP Ultrium 460e), and an autoloader with an LTO 3 drive in (Tandberg T24 autoloader, with a HP drive). Performance of the LTO 2 tapes in the LTO 2 drive is adequate and consistent. HP L&TT tells me that the tapes can be read and written at 64 MB/s, which seems in line with the performance specifications of the drive. When I perform a backup (over the network) using Symantec Backup Exec, I get about 1700 MB/min backup and verify speeds, which is slower, but still adequate. Performance of the LTO 2 tapes in the LTO 3 drive in the autoloader is a different story. HP L&TT tells me that the tapes can be read at 82 MB/s and written at 49 MB/s, which seems unusual at the write speed drop, but not the end of the world. When I perform a backup (over the network) using Symantec Backup Exec though, I get about 331 MB/min backup speed and 205 MB/min verify speeds, which is not only much slower, but also much slower for reads than for writes. Notes: The comparison testing was done on the same server, SCSI card and SCSI cable, with the same backup data set and the same tape each time. The tape and drives are error-free (according to HP L&TT and Backup Exec). The SCSI card is a U160 card, which is not normally recommended for LTO 3, but we're not writing to LTO 3 tapes at LTO 3 speeds, and a U320 SCSI card is not available to me at the moment. As I'm scratching my head to determine the reason for the performance drop, my first question is: While LTO drives can write to the previous generation LTO tapes, does doing so normally incur a performance penalty?

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  • Raid-5 Performance per spindle scaling

    - by Bill N.
    So I am stuck in a corner, I have a storage project that is limited to 24 spindles, and requires heavy random Write (the corresponding read side is purely sequential). Needs every bit of space on my Drives, ~13TB total in a n-1 raid-5, and has to go fast, over 2GB/s sort of fast. The obvious answer is to use a Stripe/Concat (Raid-0/1), or better yet a raid-10 in place of the raid-5, but that is disallowed for reasons beyond my control. So I am here asking for help in getting a sub optimal configuration to be as good as it can be. The array built on direct attached SAS-2 10K rpm drives, backed by a ARECA 18xx series controller with 4GB of cache. 64k array stripes and an 4K stripe aligned XFS File system, with 24 Allocation groups (to avoid some of the penalty for being raid 5). The heart of my question is this: In the same setup with 6 spindles/AG's I see a near disk limited performance on the write, ~100MB/s per spindle, at 12 spindles I see that drop to ~80MB/s and at 24 ~60MB/s. I would expect that with a distributed parity and matched AG's, the performance should scale with the # of spindles, or be worse at small spindle counts, but this array is doing the opposite. What am I missing ? Should Raid-5 performance scale with # of spindles ? Many thanks for your answers and any ideas, input, or guidance. --Bill Edit: Improving RAID performance The other relevant thread I was able to find, discusses some of the same issues in the answers, though it still leaves me with out an answer on the performance scaling.

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  • How to limit disk performance?

    - by DrakeES
    I am load-testing a web application and studying the impact of some config tweaks (related to disk i/o) on the overall app performance, i.e. the amount of users that can be handled simultaneously. But the problem is that I hit 100% CPU before I can see any effect of the disk-related config settings. I am therefore wondering if there is a way I could deliberately limit the disk performance so that it becomes the bottleneck and the tweaks I am trying to play with actually start impacting performance. Should I just make the hard disk busy with something else? What would serve the best for this purpose? More details (probably irrelevant, but anyway): PHP/Magento/Apache, studying the impact of apc.stat. Setting it to 0 makes APC not checking PHP scripts for modification which should increase performance where disk is the bottleneck. Using JMeter for benchmarking.

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  • Good C++ books regarding Performance?

    - by Leon
    Besides the books everyone knows about, like Meyer's 3 Effective C++/STL books, are there any other really good C++ books specifically aimed towards performance code? Maybe this is for gaming, telecommunications, finance/high frequency etc? When I say performance I mean things where a normal C++ book wouldnt bother advising because the gain in performance isn't worthwhile for 95% of C++ developers. Maybe suggestions like avoiding virtual pointers, going into great depth about inlining etc? A book going into great depth on C++ memory allocation or multithreading performance would obviously be very useful.

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  • puzzled with java if else performance

    - by user1906966
    I am doing an investigation on a method's performance and finally identified the overhead was caused by the "else" portion of the if else statement. I have written a small program to illustrate the performance difference even when the else portion of the code never gets executed: public class TestIfPerf { public static void main( String[] args ) { boolean condition = true; long time = 0L; int value = 0; // warm up test for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } else { value = 1 + 3; } } // benchmark if condition only time = System.nanoTime(); for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } } time = System.nanoTime() - time; System.out.println( "1) performance " + time ); time = System.nanoTime(); // benchmark if else condition for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } else { value = 1 + 3; } } time = System.nanoTime() - time; System.out.println( "2) performance " + time ); } } and run the test program with java -classpath . -Dmx=800m -Dms=800m TestIfPerf. I performed this on both Mac and Linux Java with 1.6 latest build. Consistently the first benchmark, without the else is much faster than the second benchmark with the else section even though the code is structured such that the else portion is never executed because of the condition. I understand that to some, the difference might not be significant but the relative performance difference is large. I wonder if anyone has any insight to this (or maybe there is something I did incorrectly). Linux benchmark (in nano) performance 1215488 performance 2629531 Mac benchmark (in nano) performance 1667000 performance 4208000

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  • Performance Testing Versus Unit Testing

    - by Mystagogue
    I'm reading Osherove's "The Art of Unit Testing," and though I've not yet seen him say anything about performance testing, two thoughts still cross my mind: Performance tests generally can't be unit tests, because performance tests generally need to run for long periods of time. Performance tests generally can't be unit tests, because performance issues too often manifest at an integration or system level (or at least the logic of a single unit test needed to re-create the performance of the integration environment would be too involved to be a unit test). Particularly for the first reason stated above, I doubt it makes sense for performance tests to be handled by a unit testing framework (such as NUnit). My question is: do my findings / leanings correspond with the thoughts of the community?

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  • What do you think of a performance engineer should have?

    - by Vance
    I believe performance tuning (or even testing) is one the most challenging for an engineer. Well, in lots of company, this is the lowest priority than others "important" thing. My purpose of opening this post is to know what do you think*good* performance engineer should have. I can list some things like: Solid database,programming knowledge. Do single thread performance testing. Good knowledge of using the load generator tools to simulate the concurrent loads. Use different tools to monitor/measure the app/db server performance status Understand and can debug the codes. Even tune the codes. Any more ideas are always appreciated!

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  • In MATLAB, how can 'preallocating' cell arrays improve performance?

    - by Alex McMurray
    I was reading this article on MathWorks about improving MATLAB performance and you will notice that one of the first suggestions is to preallocate arrays, which makes sense. But it also says that preallocating Cell arrays (that is arrays which may contain different, unknown datatypes) will improve performance. But how will doing so improve performance because the datatypes are unknown so it doesn't know how much contiguous memory it will require even if it knows the shape of the cell array, and therefore it can't preallocate the memory surely? So how does this result in any improvement in performance? I apologise if this question is better suited for StackOverflow than Programmers but it isn't asking about a specific problem so I thought it fit better here, please let me know if I am mistaken though. Any explanation would be greatly appreciated :)

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  • Does software rot refer primarily to performance, or to messy code?

    - by Kazark
    Wikipedia's definition of software rot focuses on the performance of the software. This is a different usage than I am used to; I had thought of it much more in terms of the cleanliness and design of the code—in terms of the code's having all the standard quality characteristics: readability, maintainability, etc. Now, performance is likely to go down when the code becomes unreadable, because no one knows what is going on. But does the term software rot have special reference to performance? or am I right in thinking it refers to the cleanliness of the code? or is this perhaps a case of multiple senses of the term being in common usage—from the user's perspective, it has do with performance; but for the software craftsman, it has to do more specifically with how the code reads?

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  • Simple vs Complex (but performance efficient) solution - which one to choose and when?

    - by ManojGumber
    I have been programming for a couple of years and have often found myself at a dilemma. There are two solutions - one is simple one i.e. simple approach, easier to understand and maintain. It involves some redundancy, some extra work (extra IO, extra processing) and therefore is not the most optimal solution. but other uses a complex approach,difficult to implement, often involving interaction between lot of modules and is a performance efficient solution. Which solution should I strive for when I do not have hard performance SLA to meet and even the simple solution can meet the performance SLA? I have felt disdain among my fellow developers for simple solution. Is it good practice to come up with most optimal complex solution if your performance SLA can be met by a simple solution?

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  • In the days of modern computing, in 'typical business apps' - why does performance matter?

    - by Prog
    This may seem like an odd question to some of you. I'm a hobbyist Java programmer. I have developed several games, an AI program that creates music, another program for painting, and similar stuff. This is to tell you that I have an experience in programming, but not in professional development of business applications. I see a lot of talk on this site about performance. People often debate what would be the most efficient algorithm in C# to perform a task, or why Python is slow and Java is faster, etc. What I'm trying to understand is: why does this matter? There are specific areas of computing where I see why performance matters: games, where tens of thousands of computations are happening every second in a constant-update loop, or low level systems which other programs rely on, such as OSs and VMs, etc. But for the normal, typical high-level business app, why does performance matter? I can understand why it used to matter, decades ago. Computers were much slower and had much less memory, so you had to think carefully about these things. But today, we have so much memory to spare and computers are so fast: does it actually matter if a particular Java algorithm is O(n^2)? Will it actually make a difference for the end users of this typical business app? When you press a GUI button in a typical business app, and behind the scenes it invokes an O(n^2) algorithm, in these days of modern computing - do you actually feel the inefficiency? My question is split in two: In practice, today does performance matter in a typical normal business program? If it does, please give me real-world examples of places in such an application, where performance and optimizations are important.

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  • Google I/O 2010 - Optimizing apps with the GWT Compiler

    Google I/O 2010 - Optimizing apps with the GWT Compiler Google I/O 2010 - Faster apps faster - Optimizing apps with the GWT Compiler GWT 201 Ray Cromwell The GWT compiler isn't just a Java to JavaScript transliterator. It performs many optimizations along the way. In this session, we'll show you not only the optimizations performed, but how you can get more out of the compiler itself. Learn how to speed up compiles, use -draftCompile, compile for only one locale/browser permutation, and more. For all I/O 2010 sessions, please go to code.google.com From: GoogleDevelopers Views: 7 0 ratings Time: 56:17 More in Science & Technology

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  • Optimizing code using PIL

    - by freakazo
    Firstly sorry for the long piece of code pasted below. This is my first time actually having to worry about performance of an application so I haven't really ever worried about performance. This piece of code pretty much searches for an image inside another image, it takes 30 seconds to run on my computer, converting the images to greyscale and other changes shaved of 15 seconds, I need another 15 shaved off. I did read a bunch of pages and looked at examples but I couldn't find the same problems in my code. So any help would be greatly appreciated. From the looks of it (cProfile) 25 seconds is spent within the Image module, and only 5 seconds in my code. from PIL import Image import os, ImageGrab, pdb, time, win32api, win32con import cProfile def GetImage(name): name = name + '.bmp' try: print(os.path.join(os.getcwd(),"Images",name)) image = Image.open(os.path.join(os.getcwd(),"Images",name)) except: print('error opening image;', name) return image def Find(name): image = GetImage(name) imagebbox = image.getbbox() screen = ImageGrab.grab() #screen = Image.open(os.path.join(os.getcwd(),"Images","Untitled.bmp")) YLimit = screen.getbbox()[3] - imagebbox[3] XLimit = screen.getbbox()[2] - imagebbox[2] image = image.convert("L") Screen = screen.convert("L") Screen.load() image.load() #print(XLimit, YLimit) Found = False image = image.getdata() for y in range(0,YLimit): for x in range(0,XLimit): BoxCoordinates = x, y, x+imagebbox[2], y+imagebbox[3] ScreenGrab = screen.crop(BoxCoordinates) ScreenGrab = ScreenGrab.getdata() if image == ScreenGrab: Found = True #print("woop") return x,y if Found == False: return "Not Found" cProfile.run('print(Find("Login"))')

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  • Performance of ClearCase servers on VMs?

    - by Garen
    Where I work, we are in need of upgrading our ClearCase servers and it's been proposed that we move them into a new (yet-to-be-deployed) VMmare system. In the past I've not noticed a significant problem with performance with most applications when running in VMs, but given that ClearCase "speed" (i.e. dynamic-view response times) is so latency sensitive I am concerned that this will not be a good idea. VMWare has numerous white-papers detailing performance related issues based on network traffic patterns that re-inforces my hypothesis, but nothing particularly concrete for this particular use case that I can see. What I can find are various forum posts online, but which are somewhat dated, e.g.: ClearCase clients are supported on VMWare, but not for performance issues. I would never put a production server on VM. It will work but will be slower. The more complex the slower it gets. accessing or building from a local snapshot view will be the fastest, building in a remote VM stored dynamic view using clearmake will be painful..... VMWare is best used for test environments (via http://www.cmcrossroads.com/forums?func=view&catid=31&id=44094&limit=10&start=10) and: VMware + ClearCase = works but SLUGGISH!!!!!! (windows)(not for production environment) My company tried to mandate that all new apps or app upgrades needed to be on/moved VMware instances. The VMware instance could not handle the demands of ClearCase. (come to find out that I was sharing a box with a database server) Will you know what else would be on that box besides ClearCase? Karl (via http://www.cmcrossroads.com/forums?func=view&id=44094&catid=31) and: ... are still finding we can't get the performance using dynamic views to below 2.5 times that of a physical machine. Interestingly, speaking to a few people with much VMWare experience and indeed from running builds, we are finding that typically, VMWare doesn't take that much longer for most applications and about 10-20% longer has been quoted. (via http://www.cmcrossroads.com/forums?func=view&catid=31&id=44094&limit=10&start=10) Which brings me to the more direct question: Does anyone have any more recent experience with ClearCase servers on VMware (if not any specific, relevant performance advice)?

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  • Logging hurts MySQL performance - but, why?

    - by jimbo
    I'm quite surprised that I can't see an answer to this anywhere on the site already, nor in the MySQL documentation (section 5.2 seems to have logging otherwise well covered!) If I enable binlogs, I see a small performance hit (subjectively), which is to be expected with a little extra IO -- but when I enable a general query log, I see an enormous performance hit (double the time to run queries, or worse), way in excess of what I see with binlogs. Of course I'm now logging every SELECT as well as every UPDATE/INSERT, but, other daemons record their every request (Apache, Exim) without grinding to a halt. Am I just seeing the effects of being close to a performance "tipping point" when it comes to IO, or is there something fundamentally difficult about logging queries that causes this to happen? I'd love to be able to log all queries to make development easier, but I can't justify the kind of hardware it feels like we'd need to get performance back up with general query logging on. I do, of course, log slow queries, and there's negligible improvement in general usage if I disable this. (All of this is on Ubuntu 10.04 LTS, MySQLd 5.1.49, but research suggests this is a fairly universal issue)

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  • Looking for a short term solution to improve website performance with additional server

    - by Tanim Mirza
    I am working with a small team to run an internal website running with PHP 5.3.9, MySQL 5.0.77. All the files and database are hosted on a dedicated Linux machine with the following configuration: Intel Xeon E5450 8 CPU cores @3.00GHz, 2992.498 MHz, Cache 6148 KB, Cent OS – Red Hat Enterprise Linux Server release 5.4 We started small and then the database got bigger and now the website performance degraded significantly. We often get server space overrun, mysql overloaded with too many calls, etc. We don't have much experience dealing with these issues. We recently got another server that we were thinking to use to improve performance. Since it has better configuration, some of us wanted to completely move everything to the new machine. But I am trying to find out how we can utilize both machine for optimized performance. I found options such as MySQL clustering, Load balancer, etc. I was wondering if I could get any suggestion for this situation "How to utilize two machines in short term for best performance", that would be great. By short term we are looking for something that we can deploy in a month or so. Thanks in advance for your time.

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  • Improving browser performance while using lots of tabs?

    - by Andrew
    My browsing habits cause me to open lots of windows and tabs, either related to different projects I'm working on or things I may want to read later. I use OSX and use about 5 spaces with multiple windows in each space. The problem is eventually I'll have around 200 or more tabs open (spread over 15-20 windows) that I don't want to close. Needless to say, my computer's performance starts to degrade. As I write this on my mobile, Safari on my laptop is locking up the computer. I used to use Chrome but found better performance with Safari. What I'd like to know, is there a graph of browser performance based on tab usage? I don't need a browser that keeps all tabs active. It would be great if the browser could increase performance by "putting tabs to sleep". Or if there was some sort of tool for saving a "workspace" of tabs that you could reactivate the next time you are working on that project. What sort of solution can you recommend to solve this problem?

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  • Load and Web Performance Testing using Visual Studio Ultimate 2010-Part 3

    - by Tarun Arora
    Welcome back once again, in Part 1 of Load and Web Performance Testing using Visual Studio 2010 I talked about why Performance Testing the application is important, the test tools available in Visual Studio Ultimate 2010 and various test rig topologies, in Part 2 of Load and Web Performance Testing using Visual Studio 2010 I discussed the details of web performance & load tests as well as why it’s important to follow a goal based pattern while performance testing your application. In part 3 I’ll be discussing Test Result Analysis, Test Result Drill through, Test Report Generation, Test Run Comparison, Asp.net Profiler and some closing thoughts. Test Results – I see some creepy worms! In Part 2 we put together a web performance test and a load test, lets run the test to see load test to see how the Web site responds to the load simulation. While the load test is running you will be able to see close to real time analysis in the Load Test Analyser window. You can use the Load Test Analyser to conduct load test analysis in three ways: Monitor a running load test - A condensed set of the performance counter data is maintained in memory. To prevent the results memory requirements from growing unbounded, up to 200 samples for each performance counter are maintained. This includes 100 evenly spaced samples that span the current elapsed time of the run and the most recent 100 samples.         After the load test run is completed - The test controller spools all collected performance counter data to a database while the test is running. Additional data, such as timing details and error details, is loaded into the database when the test completes. The performance data for a completed test is loaded from the database and analysed by the Load Test Analyser. Below you can see a screen shot of the summary view, this provides key results in a format that is compact and easy to read. You can also print the load test summary, this is generated after the test has completed or been stopped.         Analyse the load test results of a previously run load test – We’ll see this in the section where i discuss comparison between two test runs. The performance counters can be plotted on the graphs. You also have the option to highlight a selected part of the test and view details, drill down to the user activity chart where you can hover over to see more details of the test run.   Generate Report => Test Run Comparisons The level of reports you can generate using the Load Test Analyser is astonishing. You have the option to create excel reports and conduct side by side analysis of two test results or to track trend analysis. The tools also allows you to export the graph data either to MS Excel or to a CSV file. You can view the ASP.NET profiler report to conduct further analysis as well. View Data and Diagnostic Attachments opens the Choose Diagnostic Data Adapter Attachment dialog box to select an adapter to analyse the result type. For example, you can select an IntelliTrace adapter, click OK and open the IntelliTrace summary for the test agent that was used in the load test.   Compare results This creates a set of reports that compares the data from two load test results using tables and bar charts. I have taken these screen shots from the MSDN documentation, I would highly recommend exploring the wealth of knowledge available on MSDN. Leaving Thoughts While load testing the application with an excessive load for a longer duration of time, i managed to bring the IIS to its knees by piling up a huge queue of requests waiting to be processed. This clearly means that the IIS had run out of threads as all the threads were busy processing existing request, one easy way of fixing this is by increasing the default number of allocated threads, but this might escalate the problem. The better suggestion is to try and drill down to the actual root cause of the problem. When ever the garbage collection runs it stops processing any pages so all requests that come in during that period are queued up, but realistically the garbage collection completes in fraction of a a second. To understand this better lets look at the .net heap, it is divided into large heap and small heap, anything greater than 85kB in size will be allocated to the Large object heap, the Large object heap is non compacting and remember large objects are expensive to move around, so if you are allocating something in the large object heap, make sure that you really need it! The small object heap on the other hand is divided into generations, so all objects that are supposed to be short-lived are suppose to live in Gen-0 and the long living objects eventually move to Gen-2 as garbage collection goes through.  As you can see in the picture below all < 85 KB size objects are first assigned to Gen-0, when Gen-0 fills up and a new object comes in and finds Gen-0 full, the garbage collection process is started, the process checks for all the dead objects and assigns them as the valid candidate for deletion to free up memory and promotes all the remaining objects in Gen-0 to Gen-1. So in the future when ever you clean up Gen-1 you have to clean up Gen-0 as well. When you fill up Gen – 0 again, all of Gen – 1 dead objects are drenched and rest are moved to Gen-2 and Gen-0 objects are moved to Gen-1 to free up Gen-0, but by this time your Garbage collection process has started to take much more time than it usually takes. Now as I mentioned earlier when garbage collection is being run all page requests that come in during that period are queued up. Does this explain why possibly page requests are getting queued up, apart from this it could also be the case that you are waiting for a long running database process to complete.      Lets explore the heap a bit more… What is really a case of crisis is when the objects are living long enough to make it to Gen-2 and then dying, this is definitely a high cost operation. But sometimes you need objects in memory, for example when you cache data you hold on to the objects because you need to use them right across the user session, which is acceptable. But if you wanted to see what extreme caching can do to your server then write a simple application that chucks in a lot of data in cache, run a load test over it for about 10-15 minutes, forcing a lot of data in memory causing the heap to run out of memory. If you get to such a state where you start running out of memory the IIS as a mode of recovery restarts the worker process. It is great way to free up all your memory in the heap but this would clear the cache. The problem with this is if the customer had 10 items in their shopping basket and that data was stored in the application cache, the user basket will now be empty forcing them either to get frustrated and go to a competitor website or if the customer is really patient, give it another try! How can you address this, well two ways of addressing this; 1. Workaround – A x86 bit processor only allows a maximum of 4GB of RAM, this means the machine effectively has around 3.4 GB of RAM available, the OS needs about 1.5 GB of RAM to run efficiently, the IIS and .net framework also need their share of memory, leaving you a heap of around 800 MB to play with. Because Team builds by default build your application in ‘Compile as any mode’ it means the application is build such that it will run in x86 bit mode if run on a x86 bit processor and run in a x64 bit mode if run on a x64 but processor. The problem with this is not all applications are really x64 bit compatible specially if you are using com objects or external libraries. So, as a quick win if you compiled your application in x86 bit mode by changing the compile as any selection to compile as x86 in the team build, you will be able to run your application on a x64 bit machine in x86 bit mode (WOW – By running Windows on Windows) and what that means is, you could use 8GB+ worth of RAM, if you take away everything else your application will roughly get a heap size of at least 4 GB to play with, which is immense. If you need a heap size of more than 4 GB you have either build a software for NASA or there is something fundamentally wrong in your application. 2. Solution – Now that you have put a workaround in place the IIS will not restart the worker process that regularly, which means you can take a breather and start working to get to the root cause of this memory leak. But this begs a question “How do I Identify possible memory leaks in my application?” Well i won’t say that there is one single tool that can tell you where the memory leak is, but trust me, ‘Performance Profiling’ is a great start point, it definitely gets you started in the right direction, let’s have a look at how. Performance Wizard - Start the Performance Wizard and select Instrumentation, this lets you measure function call counts and timings. Before running the performance session right click the performance session settings and chose properties from the context menu to bring up the Performance session properties page and as shown in the screen shot below, check the check boxes in the group ‘.NET memory profiling collection’ namely ‘Collect .NET object allocation information’ and ‘Also collect the .NET Object lifetime information’.    Now if you fire off the profiling session on your pages you will notice that the results allows you to view ‘Object Lifetime’ which shows you the number of objects that made it to Gen-0, Gen-1, Gen-2, Large heap, etc. Another great feature about the profile is that if your application has > 5% cases where objects die right after making to the Gen-2 storage a threshold alert is generated to alert you. Since you have the option to also view the most expensive methods and by capturing the IntelliTrace data you can drill in to narrow down to the line of code that is the root cause of the problem. Well now that we have seen how crucial memory management is and how easy Visual Studio Ultimate 2010 makes it for us to identify and reproduce the problem with the best of breed tools in the product. Caching One of the main ways to improve performance is Caching. Which basically means you tell the web server that instead of going to the database for each request you keep the data in the webserver and when the user asks for it you serve it from the webserver itself. BUT that can have consequences! Let’s look at some code, trust me caching code is not very intuitive, I define a cache key for almost all searches made through the common search page and cache the results. The approach works fine, first time i get the data from the database and second time data is served from the cache, significant performance improvement, EXCEPT when two users try to do the same operation and run into each other. But it is easy to handle this by adding the lock as you can see in the snippet below. So, as long as a user comes in and finds that the cache is empty, the user locks and starts to get the cache no more concurrency issues. But lets say you are processing 10 requests per second, by the time i have locked the operation to get the results from the database, 9 other users came in and found that the cache key is null so after i have come out and populated the cache they will still go in to get the results again. The application will still be faster because the next set of 10 users and so on would continue to get data from the cache. BUT if we added another null check after locking to build the cache and before actual call to the db then the 9 users who follow me would not make the extra trip to the database at all and that would really increase the performance, but didn’t i say that the code won’t be very intuitive, may be you should leave a comment you don’t want another developer to come in and think what a fresher why is he checking for the cache key null twice !!! The downside of caching is, you are storing the data outside of the database and the data could be wrong because the updates applied to the database would make the data cached at the web server out of sync. So, how do you invalidate the cache? Well if you only had one way of updating the data lets say only one entry point to the data update you can write some logic to say that every time new data is entered set the cache object to null. But this approach will not work as soon as you have several ways of feeding data to the system or your system is scaled out across a farm of web servers. The perfect solution to this is Micro Caching which means you cache the query for a set time duration and invalidate the cache after that set duration. The advantage is every time the user queries for that data with in the time span for which you have cached the results there are no calls made to the database and the data is served right from the server which makes the response immensely quick. Now figuring out the appropriate time span for which you micro cache the query results really depends on the application. Lets say your website gets 10 requests per second, if you retain the cache results for even 1 minute you will have immense performance gains. You would reduce 90% hits to the database for searching. Ever wondered why when you go to e-bookers.com or xpedia.com or yatra.com to book a flight and you click on the book button because the fare seems too exciting and you get an error message telling you that the fare is not valid any more. Yes, exactly => That is a cache failure! These travel sites or price compare engines are not going to hit the database every time you hit the compare button instead the results will be served from the cache, because the query results are micro cached, its a perfect trade-off, by micro caching the results the site gains 100% performance benefits but every once in a while annoys a customer because the fare has expired. But the trade off works in the favour of these sites as they are still able to process up to 30+ page requests per second which means cater to the site traffic by may be losing 1 customer every once in a while to a competitor who is also using a similar caching technique what are the odds that the user will not come back to their site sooner or later? Recap   Resources Below are some Key resource you might like to review. I would highly recommend the documentation, walkthroughs and videos available on MSDN. You can always make use of Fiddler to debug Web Performance Tests. Some community test extensions and plug ins available on Codeplex might also be of interest to you. The Road Ahead Thank you for taking the time out and reading this blog post, you may also want to read Part I and Part II if you haven’t so far. If you enjoyed the post, remember to subscribe to http://feeds.feedburner.com/TarunArora. Questions/Feedback/Suggestions, etc please leave a comment. Next ‘Load Testing in the cloud’, I’ll be working on exploring the possibilities of running Test controller/Agents in the Cloud. See you on the other side! Thank You!   Share this post : CodeProject

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  • Effects of HTTP/TCP connection handshakes and server performance

    - by Blankman
    When running apache bench on the same server as the website like: ab -n 1000 -c 10 localhost:8080/ I am most probably not getting accurate results when compared to users hitting the server from various locations. I'm trying to understand how or rather why this will effect real world performance since a user in china will have different latency issues when compared to someone in the same state/country. Say my web server has a maximum thread limit of 100. Can someone explain in detail how end user latency can/will effect server performance. I'm assuming here that each request will be computed equally at say 10ms. What I'm not understand is how external factors can effect overal server performance, specifically internet connections (location, or even device like mobile) and http/tcp handshakes etc.

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  • Query performance counters from powershell

    - by Frane Borozan
    I am trying this script to query performance counters in different localized windows server versions. http://www.powershellmagazine.com/2013/07/19/querying-performance-counters-from-powershell/ Everything works as in the article, well partially :-) I am trying to access a counter ID 3906 Terminal Services Session and works well for English windows. However for example in French and German that counter doesn't exist under that ID. I think I figured to find the exact counter under ID 1548 in french and German, but that ID in English is something completely different. Anybody seen this behavior on the performance counters?

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  • RAID Array performance on an HP Proliant ML350 G5 Smart Array E200i

    - by Nate Pinchot
    We have a client who is complaining about performance of an application which utilizes an MS SQL database. They do not believe the performance issues are the fault of the application itself. The Smart Array E200i RAID controller has 128MB cache and we have the cache set to 75% read/25% write. The disk array set to enable write caching. Recently we ran a disk performance test using SQLIO based on this guide. We used a 10 GB file for the test found that the average sequential read rate was ~60 MB/sec (megabytes/sec) and the average random read rate was ~30 MB/sec. Are these numbers on par for what the server should be performing? Better than on par? Horrible? Amazing?

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