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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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  • How to virtualize a qnap NAS with virtualbox?

    - by l1zard
    I want to deploy an owncloud based cloud service at a qnap NAS. And i need to test it before we can use it on the production system. there is a french site which made it possible to download a virtualbox disk image but the documentaion about how to use this image is very poor or in french, so i can't read it. Has anybody ever been successfully virtualized a qnap NAS and could tell me exactly how this can be acclomlish?

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  • How can I make Webalizer work with rolling apache logs?

    - by Simon
    I am using Webalizer to view my site stats, and it's working ok with one exception; I have log rolling configured so my log directory looks something like this: :/var/log/apache2$ ls access.log access.log.1 access.log.2.gz access.log.3.gz ... Webalizer ends up only storing the last ~4 days each time it runs, so I only ever get a rolling window of stats rather than the full month. How can I make Webalizer process the full set of logs?

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  • JBOD with PERC H810

    - by primero
    I'm wondering if anybody has ever used Dell storage products like the MD3220 array in a JBOD configuration. From what I can tell only perc h810 will work for external JBOD but that is not terribly specific, and for some reason I couldn't find many examples on the web of people configuring dell storage products as JBOD. My question is: Is it possible to connect to am MD3220 array, or other Dell arrays using a PERC h810 controller and use it as JBOD, and if so do I have to configure every disk in the array as a RAID 0 volume?

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  • Linux: how to use Jellyfish from Jack Meterbridge?

    - by klox
    dear all, i have installed Meterbridge. But,i'm just need to use Jellyfish from this package. I changed the Meterbridge properties become: /usr/bin/meterbridge -t jf alsa_pcm:playback_1 alsa_pcm:playback_2 My problem come here, i can open the Jellyfish window but i can't show the wave from input jack. How should i do? have you ever try this? some tell me to set up the Jack Audio Connection Kit, But i don't understand how to do it because i'm new for this

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  • Opensource Dns based incoming Load balancing ?

    - by sahil
    Hi, I am using Linkproof device for incoming load balancing based on which is based on dns. For example my linkprrof have 3 isp link.... it also act as a dns sevrer for my sites...so when someone connect me by using my dns name my linkprrof give them ip from 3 isp which ever is responding fast. so is there any same kind of open source solution for dns based incoming load balance is possible ??? sahil

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  • mac os x - detect file system read

    - by quano
    I want to know what files a specific application is trying to access on my disc. I know that you can use fs_usage, but this outputs events from all applications. I know that you can target a single application, but only one that is already running. I want to detect all readfile-events an application is trying to do, ever since it is started. I don't want to miss out on any event. How do you achieve this?

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  • WiseCustomCalla.dll ? What is that?

    - by HeavyWave
    I have a few folders in my Windows folder (I'm running Windows 7) like this: C:\Windows\1C4551A64743409391E41477CD655043.TMP\WiseCustomCalla.dll All they contain is WiseCustomCalla.dll. I've read that it is part of McAfee antivirus or whatever. The problem is: I have never ever installed any antivirus software on my machine. What is this file and what is it doing on my machine? I am also using Steam and PunkBuster if that helps.

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  • Windows 7 boot problem (with colorful blinking smilies)

    - by Ishmael Smyrnow
    I put my computer (Windows 7) to sleep, and a couple hours later, tried to wake it back up, but the monitor wouldn't come back on. I did a hard reset (held power button), but I still couldn't get the monitor to show anything. I plugged it into my laptop, and the monitor works fine. I then swapped out the video card with an older one I have. The monitor came on and started showing the boot process. However, shortly after the Windows 7 animated logo came up, the screen went blank, it made this weird beeping noise, and I seen the strangest thing ever. Small, colorful blocks started to fill my screen, and flash, as if something was loading. Inside of those blocks, were smilies (like the ASCII character kind). This continued for about a minute, then the computer rebooted. It scared the sh!t out of me. I've never had a virus before, and I'm savvy enough to keep myself from one, but I'm wondering if that's what it was. I've been using computers for ages, and never seen anything quite like this. Has anyone ever seen something like this? I'm doing hardware diagnostics before trying to boot into Windows again. Hopefully I can figure this out, but I thought I would consult the SU community while I wait on these results. -- UPDATE -- I did a Memory Diagnostic, which turned up nothing. I also booted into Safe Mode no problem, and scheduled a disk check on both of my drives (I dual boot XP & 7). I was feeling good, and tried putting my regular video card back in, and the monitor won't display anything with it. Also, even though the monitor displays nothing, the system sounds like it's booting up. However, I hear a clicking in one of my hard drives that isn't there with the older video card. Could this be a problem with my hard drive, video card, or PSU? PSU makes sense, except for the fact I've been using the same setup for over a year, and the video card doesn't require it's own power plug thing.

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  • Daisy-chaining network switches with multiple cables

    - by user72153
    This might just be the dumbest question you'll ever read, but I digress. Say I have two 100Mbps Ethernet switches with 2 computers on each, connected together by a single cable. This way, the two PCs on each switch share the 100Mbps bandwidth with the others. If I added another cable between the 2 switches, would there be 200Mbps throughput available between the switches? Or am I completely off my rocker? Thanks for the help.

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  • ActiveSync / Exchange 2007 password expiration buffer on device

    - by Matt Hamende
    I'm trying to determine if there is any buffer of time from the time a password expires in AD to the time that users would stop receiving email on their mobile devices our setup is Exchange 2007 ActiveSync DC's are Server 2008 R2 primarily Android shop, with maybe a few iOS devices I've heard some rumors of people still receiving email after their password expired / changed on the domain, just want to see if anyone else has ever heard of this. Did a bit more reading, read about Token Cache in IIS 7.0 and 15min lagtime, still would like to hear any thoughts about this.

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  • Use synergy with KVM

    - by Mr. Man
    I am using synergy on a Linux Mint server with a Mac as the client. I also have a physical KVM switch. The problem I have is that when ever I switch the physical KVM to my Mac, synergy stops working as in the keyboard and mouse don't work with the Mac. Thanks in advance!

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  • Make IE stop asking me to install adobe flash player

    - by Sam
    I don't have adobe flash player installed, and don't miss the flashing ads a bit. The only thing that annoys me: IE8 keeps asking me "this web site wants to install Adobe Flash Player", and I want to get rid of this question. I don't want to install it, not now, not ever. So how do I make IE stop asking me about it?

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  • Bind9 wont start on ubuntu 9.10

    - by Logikdev
    Ever since i've upgraded to ubuntu 9.10, bind9 wont start: Setting up bind9 (1:9.6.1.dfsg.P1-3ubuntu0.2) ... * Starting domain name service... bind9 [fail] invoke-rc.d: initscript bind9, action "start" failed. dpkg: error processing bind9 (--configure): subprocess installed post-installation script returned error exit status 1 Errors were encountered while processing: bind9 E: Sub-process /usr/bin/dpkg returned an error code (1) Any ideas?

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  • sqlldr job not running through Autosys

    - by Frank
    I have a shell script that if run manually or via Cron executes fine and loads a delimited file using sqlldr to the database successfully. However via Autosys the script executes, sqlldr says it was successful, however the data is never actually loaded into the database. Has anyone ever experienced this before with the sqlldr/Autosys combination, and if so, knows of a workaround/fix?

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  • Obscure Operating Systems

    - by DLH
    Do you ever get the urge to try random obscure operating systems? I think it's sometimes just fun to use systems that are not widely used. What obscure operating systems have you tried (or have thought about trying)? I've been looking into Haiku lately.

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