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WPA kicks off many short lived threads that do nothing but fight each other for locks RRS feed

  • Question

  • I have been noticing that WPA tends to be a bit slow at expanding tree nodes. Alas, if only I had a tool available to investigate such things… oh, right!

    So here we see the rather curious CPU usage pattern WPA shows while expanding a group of about 40,000 stack traces (taking over 300ms):

    Each one of the big humps involves kicking off 8 new threads, each of which hangs around for just 50ms or so. And the tiny little bump at 5.82 seconds involves 4 new threads that only run for about 1ms each!

    That seems less than ideal... what do the stacks show for those periods?

    Stack, Count, Weight (in view) (ms) microsoft.performance.shell.dll!Microsoft.Performance.Shell.Tables.Columns.StackFrameTagPathNodeColumn+StackFrameTagPathNodeColumnGenerator`2[System.__Canon,Microsoft.Performance.Shell.Tables.Columns.Generators.CachedOnFirstUseColumnGenerator`2[Microsoft.Performance.PerfCore4.StackTopCPtr,M, 593, 592.057600   |- microsoft.performance.shell.dll!Microsoft.Performance.Shell.Stacks.StackFrameTagsReferenceService::FrameTagsFromTop 0x0, 585, 583.954800   |    |- clr.dll!JIT_MonEnterWorker_InlineGetThread_GetThread_PatchLabel, , 542, 540.769400   |    |- microsoft.performance.core4.interop.dll!Microsoft.Performance.PerfCore4.StackFrameTagMapperExtensions::FrameTagsFromTop 0x0, 37, 37.151800   |    |- microsoft.performance.shell.dll!Microsoft.Performance.Shell.Stacks.StackFrameTagsReferenceService::FrameTagsFromTop 0x0<itself>, 3, 2.980300

     

    Spinning up all those threads to get worse than single threaded performance seems not so great. And why is it doing it twice? I've only expanded a single node!



    • Edited by Zhentar Thursday, April 25, 2019 7:48 PM Fix images
    Saturday, April 13, 2019 11:08 PM

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