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High context switching

  • July 14, 2008 at 9:35 am

    #126452

    All,

    My configuration: 4*quadcore CPU, MSSQL2K5 sp2+cu6, 32GB RAM (28GB for MSSQL), Windows server2003, Cluster

    Running Axapta 3.0 database (100GB, 16 datafiles), 200 users connected.

    Since 11.00 this morning, context switching changed from 25.000 to 250.000

    3 CPUs are at 80%, the rest operates normal.

    Tempdb was blown up by a user, killed that user (in the database :D)

    It's 17:30 now, with 60 users and context switching is still 250.000.

    Problem might be caused by an Axapta (application) server, but not sure

    Questions:

    - How can i determine what's causing this high switching?

    - Somebody else who have this experience?

    thanks!

    Wilfred
    The best things in life are the simple things

  • July 14, 2008 at 9:38 am

    #842504

    forgot to say : it's 64bit

    Wilfred
    The best things in life are the simple things

  • July 14, 2008 at 9:52 am

    #842515

    you can use windows Fibers(Lightweight Pooling) mode setting in SQL Server 2005.

    SQLMail will not be suported if you are running in Lightweight pooling mode. This occurs when the OS/application is forced to change the executing thread across processor's.

    so if the CPU usage is higher or there is I/O contention, the higher the context switching, and will result in lower throughput.

    so the number of context switches should be as small as possible.

    So Read this: http://support.microsoft.com/default.aspx?scid=kb;%5BLN%5D;319942

    Maninder
    www.dbanation.com

  • July 14, 2008 at 12:17 pm

    #842621

    Thanks for your reply, but that's not what I'm looking for.

    I'm just curious to know what's causing this problem and how I can identify these types of problems.

    Implementing NT fibers is for me like ignoring the "no oil" alertsign in my car ...

    Wilfred
    The best things in life are the simple things

  • July 16, 2008 at 2:00 am

    #843583

    UPDATE:

    For some reason, somebody blew up the tempdb. This caused a Quest databaseperformance collector (quest_sccollector64.exe) to go mad and hammered the CPU. After killing this process, SQL is normal (including context switching) :Wow:

    I'm still investigating who blew up the TempDb, but at least I got my SQL back to normal.

    If somebody has some interesting facts/site about context switching, let me know ...

    Wilfred
    The best things in life are the simple things

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