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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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  • Linux RAID-0 performance doesn't scale up over 1 GB/s

    - by wazoox
    I have trouble getting the max throughput out of my setup. The hardware is as follow : dual Quad-Core AMD Opteron(tm) Processor 2376 16 GB DDR2 ECC RAM dual Adaptec 52245 RAID controllers 48 1 TB SATA drives set up as 2 RAID-6 arrays (256KB stripe) + spares. Software : Plain vanilla 2.6.32.25 kernel, compiled for AMD-64, optimized for NUMA; Debian Lenny userland. benchmarks run : disktest, bonnie++, dd, etc. All give the same results. No discrepancy here. io scheduler used : noop. Yeah, no trick here. Up until now I basically assumed that striping (RAID 0) several physical devices should augment performance roughly linearly. However this is not the case here : each RAID array achieves about 780 MB/s write, sustained, and 1 GB/s read, sustained. writing to both RAID arrays simultaneously with two different processes gives 750 + 750 MB/s, and reading from both gives 1 + 1 GB/s. however when I stripe both arrays together, using either mdadm or lvm, the performance is about 850 MB/s writing and 1.4 GB/s reading. at least 30% less than expected! running two parallel writer or reader processes against the striped arrays doesn't enhance the figures, in fact it degrades performance even further. So what's happening here? Basically I ruled out bus or memory contention, because when I run dd on both drives simultaneously, aggregate write speed actually reach 1.5 GB/s and reading speed tops 2 GB/s. So it's not the PCIe bus. I suppose it's not the RAM. It's not the filesystem, because I get exactly the same numbers benchmarking against the raw device or using XFS. And I also get exactly the same performance using either LVM striping and md striping. What's wrong? What's preventing a process from going up to the max possible throughput? Is Linux striping defective? What other tests could I run?

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  • Books and resources for Java Performance tuning - when working with databases, huge lists

    - by Arvind
    Hi All, I am relatively new to working on huge applications in Java. I am working on a Java web service which is pretty heavily used by various clients. The service basically queries the database (hibernate) and then works with a lot of Lists (there are adapters to convert list returned from DB to the interface which the service publishes) and I am seeing lot of issues with the service like high CPU usage or high heap space. While I can troubleshoot the performance issues using a profiler, I want to actually learn about what all I need to take care when I actually write code. Like what kind of List to use or things like using StringBuilder instead of String, etc... Is there any book or blogs which I can refer which will help me while I write new services? Also my application is multithreaded - each service call from a client is a new thread, and I want to know some best practices around that area as well. I did search the web but I found many tips which are not relevant in the latest Java 6 releases, so wanted to know what kind of resources would help a developer starting out now on Java for heavily used applications. Arvind

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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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  • After writing SQL statements in MySQL, how to measure the speed / performance of them?

    - by Jian Lin
    I saw something from an "execution plan" article: 10 rows fetched in 0.0003s (0.7344s) How come there are 2 durations shown? What if I don't have large data set yet. For example, if I have only 20, 50, or even just 100 records, I can't really measure how faster 2 different SQL statements compare in term of speed in real life situation? In other words, there needs to be at least hundreds of thousands of records, or even a million records to accurately compares the performance of 2 different SQL statements?

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  • Harness MySQL's Continued Performance Tuning Improvements

    - by Antoinette O'Sullivan
    To fully harness the continued improvements in performance tuning you get with MySQL, take the MySQL Performance Tuning course. This 4 day class teaches you practical, safe, highly efficient ways to optimize performance for the MySQL Server. You will learn the skills needed to use tools for monitoring, evaluating and tuning.  You can take this course in the following three ways: Training-on-Demand: Follow this course at your own pace and from your own desk with streaming video of instructor delivery and booking time to follow hands-on exercises at your own convenience. Live-Virtual: Attend a live instructor-led event from your own desk. Choose from the numerous events on the schedule. In-Class:  Travel to an education center to follow this class. A sample of events on the schedule is shown below:  Location  Date  Delivery Language  Tokyo, Japan  19 November 2012  Japanese  Mechelen, Belgium  4 February 2013  English  London, England  19 November 2012  English  Budapest, Hungary  21 May 2013  Hungarian  Milan, Italy  14 January 2013  Italian  Rome, Italy  3 December 2012  Italian  Riga, Latvia  10 December 2012  Latvian  Amsterdam, Netherlands  7 January 2013  Dutch  Nieuwegein, Netherlands  26 November 2012  Dutch  Warsaw, Poland  3 December 2012  Polish  Lisbon, Portugal  4 February 2013  European Portugese  Porto, Portugal  4 February 2013  European Portugese  Barcelona, Spain  25 March 2013  Spanish  Madrid, Spain  17 December 2012  Spanish  Sydney, Australia  26 November 2012  English  Edmonton, Canada  10 December 2012  English  Montreal, Canada  26 November 2012  English  Ottawa, Canada  26 November 2012  English  Toronto, Canada  26 November 2012  English  Vancouver, Canada  10 December 2012  English  Sao Paolo, Brazil  26 November 2012  Brazilan Portugese For more information on this class or to know more about other courses on the authentic MySQL curriculum. see http://oracle.com/education/mysql. Note, many organizations deploy both Oracle Database and MySQL side by side to serve different needs, and as a database professional you can find training courses on both topics at Oracle University! Check out the upcoming Oracle Database training courses and MySQL training courses. Even if you're only managing Oracle Databases at this point of time, getting familiar with MySQL will broaden your career path with growing job demand.

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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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  • SQL SERVER – BI Quiz Hint – Performance Tuning Cubes – Hints

    - by pinaldave
    I earlier wrote about SQL BI Quiz over here and here. The details of the quiz is here: Working with huge data is very common when it is about Data Warehousing. It is necessary to create Cubes on the data to make it meaningful and consumable. There are cases when retrieving the data from cube takes lots of the time. Let us assume that your cube is returning you data very quickly. Suddenly on one day it is returning the data very slowly. What are the three things will you to diagnose this. After diagnose what you will do to resolve performance issue. Participate in my question over here I required BI Expert Jason Thomas to help with few hints to blog readers. He is one of the leading SSAS expert and writes a complicated subject in simple words. If queries were executing properly before but now take a long time to return the data, it means that there has been a change in the environment in which it is running. Some possible changes are listed below:-  1) Data factors:- Compare the data size then and now. Increase in data can result in different execution times. Poorly written queries as well as poor design will not start showing issues till the data grows. How to find it out? (Ans : SQL Server profiler and Perfmon Counters can be used for identifying the issues and performance  tuning the MDX queries)  2) Internal Factors:- Is some slow MDX query / multiple mdx queries running at the same time, which was not running when you had tested it before? Is there any locking happening due to proactive caching or processing operations? Are the measure group caches being cleared by processing operations? (Ans : Again, profiler and perfmon counters will help in finding it out. Load testing can be done using AS Performance Workbench (http://asperfwb.codeplex.com/) by running multiple queries at once)  3) External factors:- Is some other application competing for the same resources?  HINT : Read “Identifying and Resolving MDX Query Performance Bottlenecks in SQL Server 2005 Analysis Services” (http://sqlcat.com/whitepapers/archive/2007/12/16/identifying-and-resolving-mdx-query-performance-bottlenecks-in-sql-server-2005-analysis-services.aspx) Well, these are great tips. Now win big prizes by participate in my question over here. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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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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  • Tuning Distributed Applications to Access Big Data

    Distributed applications are just that: distributed across one or more hardware platforms across the enterprise. The database administrator (DBA) has the unenviable task of monitoring these environments and configuring and tuning the database server to meet multiple needs. As multiple distributed applications now require access to a very large data store, what tuning options are available to help? Get your SQL Server database under version control now!Version control is standard for applications, but databases haven’t caught up. So how can you bring database development up to speed? Why should you start? Find out…

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  • Advisor Webcast ?7?!~ OBIEE 11g ?????·??????????????? ??????

    - by yvetteyvette
    Advisor Webcast ?7?!~ OBIEE 11g ?????·??????????????? ?????? 2013???????????? Advisor Webcast? ??????????????????? ??????????????????7?????Oracle Business Intelligence Enterprise Edition (?? OBIEE)???????OBIEE 11g ?????·?????????????????10?14?(?)16????????? OBIEE ????????????????????????????????????????????????????????????????? Advisor Webcast ??: ??????????????????????????????????????·??????????? ????Web???????Web Conferencing????????????????????????????????????????????????(Q&A)??????????????? OBIEE 11g ?????·??????????????? ??: 2014?10?14?(?) 16?~17? ??: ???????????????????????????? ?????????????????????????? ??????????????????????? ????: ?????????????(My Oracle Support ???????????)

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  • Openfiler iSCSI performance

    - by Justin
    Hoping someone can point me in the right direction with some iSCSI performance issues I'm having. I'm running Openfiler 2.99 on an older ProLiant DL360 G5. Dual Xeon processor, 6GB ECC RAM, Intel Gigabit Server NIC, SAS controller with and 3 10K SAS drives in a RAID 5. When I run a simple write test from the box directly the performance is very good: [root@localhost ~]# dd if=/dev/zero of=tmpfile bs=1M count=1000 1000+0 records in 1000+0 records out 1048576000 bytes (1.0 GB) copied, 4.64468 s, 226 MB/s So I created a LUN, attached it to another box I have running ESXi 5.1 (Core i7 2600k, 16GB RAM, Intel Gigabit Server NIC) and created a new datastore. Once I created the datastore I was able to create and start a VM running CentOS with 2GB of RAM and 16GB of disk space. The OS installed fine and I'm able to use it but when I ran the same test inside the VM I get dramatically different results: [root@localhost ~]# dd if=/dev/zero of=tmpfile bs=1M count=1000 1000+0 records in 1000+0 records out 1048576000 bytes (1.0 GB) copied, 26.8786 s, 39.0 MB/s [root@localhost ~]# Both servers have brand new Intel Server NIC's and I have Jumbo Frames enabled on the switch, the openfiler box as well as the VMKernel adapter on the ESXi box. I can confirm this is set up properly by using the vmkping command from the ESXi host: ~ # vmkping 10.0.0.1 -s 9000 PING 10.0.0.1 (10.0.0.1): 9000 data bytes 9008 bytes from 10.0.0.1: icmp_seq=0 ttl=64 time=0.533 ms 9008 bytes from 10.0.0.1: icmp_seq=1 ttl=64 time=0.736 ms 9008 bytes from 10.0.0.1: icmp_seq=2 ttl=64 time=0.570 ms The only thing I haven't tried as far as networking goes is bonding two interfaces together. I'm open to trying that down the road but for now I am trying to keep things simple. I know this is a pretty modest setup and I'm not expecting top notch performance but I would like to see 90-100MB/s. Any ideas?

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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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  • mysql medium int vs. int performance?

    - by aviv
    Hi, I have a simple users table, i guess the maximum users i am going to have is 300,000. Currently i am using: CREATE TABLE users ( id INT UNSIGEND AUTOINCEREMENT PRIMARY KEY, .... Of course i have many other tables that the users(id) is a FOREIGN KEY in them. I read that since the id is not going to use the full maximum of INT it is better to use: MEDIUMINT and it will give better performance. Is it true? (I am using mysql on Windows Server 2008) Thanks.

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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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  • Performance tuning of tabular data models in Analysis Services

    - by Greg Low
    More and more practical information around working with tabular data models is starting to appear as more and more sites get deployed.At SQL Down Under, we've already helped quite a few customers move to tabular data models in Analysis Services and have started to collect quite a bit of information on what works well (and what doesn't) in terms of performance of these models. We've also been running a lot of training on tabular data models.It was great to see a whitepaper on the performance of these models released today.Performance Tuning of Tabular Models in SQL Server 2012 Analysis Services was written by John Sirmon, Greg Galloway, Cindy Gross and Karan Gulati. You'll find it here: http://msdn.microsoft.com/en-us/library/dn393915.aspx

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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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