Groups > comp.programming.threads > #1494

Thread scaling in Windows

Newsgroups	comp.programming.threads
Subject	Thread scaling in Windows
From	Paavo Helde <myfirstname@osa.pri.ee>
Organization	PKI
Message-ID	<XnsA1CFD0BECDBADmyfirstnameosapriee@216.196.109.131> (permalink)
Date	2013-05-29 12:31 -0500

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Hi group,

We have a portable C++ app using Boost mutexes and doing some memory and 
cpu intensive calculations. The problem is it seems to scale much better 
in Linux than in Windows. We are testing on an Intel Ivy Bridge machine 
with 12 cores, 24 with hyperthreading. On Linux the performance goes more 
or less linearly up when increasing the number of worker threads, up to 
some 18 threads or so. When the same machine is booted into Windows (Win7 
Pro 64-bit), the performance goes up to 4 threads (even slightly 
outperforming Linux), then actually starts to come down so that adding 
more worker threads actually makes it slower. 

We ran it also in the Intel VTune analyzer, with 24 worker threads. It 
reported that we have excellent thread concurrency, ca 24 threads running 
or runnable by the OS at every time. However, the cpu utilization was 
several times worse, meaning that the runnable threads actually did not 
run. The laconic help in VTune says that concurrency may be better than 
cpu usage if threads are "scheduled for running, but do not actually 
spend cpu time", which does not help much. 

What might be reasons for such behavior? Obvious thing like disabling 
virus scanners and ensuring no other apps are running we have already 
done. How to study it more, in VTune or otherwise (not much experience 
with VTune actually so don't know where to look exactly)?

TIA
Paavo

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Thread

Thread scaling in Windows Paavo Helde <myfirstname@osa.pri.ee> - 2013-05-29 12:31 -0500
  Re: Thread scaling in Windows Robert Miles <robertmilesxyz@gmail.com> - 2013-05-29 17:26 -0700
    Re: Thread scaling in Windows Paavo Helde <myfirstname@osa.pri.ee> - 2013-05-30 16:11 -0500
      Re: Thread scaling in Windows Gerald Breuer <Gerald.Breuer@googlemail.com> - 2013-05-31 03:44 +0200
        Re: Thread scaling in Windows Paavo Helde <myfirstname@osa.pri.ee> - 2013-05-31 00:29 -0500
  Re: Thread scaling in Windows Marcel Müller <news.5.maazl@spamgourmet.org> - 2013-05-30 23:28 +0200
    Re: Thread scaling in Windows Paavo Helde <myfirstname@osa.pri.ee> - 2013-05-30 17:52 -0500
      Re: Thread scaling in Windows Melzzzzz <mel@zzzzz.com> - 2013-05-31 04:18 +0200
      Re: Thread scaling in Windows Robert Wessel <robertwessel2@yahoo.com> - 2013-05-31 01:11 -0500
        Re: Thread scaling in Windows Paavo Helde <myfirstname@osa.pri.ee> - 2013-06-01 12:15 -0500
          Re: Thread scaling in Windows Paavo Helde <myfirstname@osa.pri.ee> - 2013-06-01 16:52 -0500
            Re: Thread scaling in Windows [SOLVED] Paavo Helde <myfirstname@osa.pri.ee> - 2013-06-03 12:00 -0500
              Re: Thread scaling in Windows [SOLVED] Casper H.S. Dik <Casper.Dik@OrSPaMcle.COM> - 2013-06-04 08:16 +0000
              Re: Thread scaling in Windows [SOLVED] Noob <root@127.0.0.1> - 2013-06-04 10:25 +0200
      Re: Thread scaling in Windows Marcel Müller <news.5.maazl@spamgourmet.org> - 2013-05-31 15:53 +0200
        Re: Thread scaling in Windows Paavo Helde <myfirstname@osa.pri.ee> - 2013-05-31 12:57 -0500
          Re: Thread scaling in Windows Marcel Müller <news.5.maazl@spamgourmet.org> - 2013-05-31 22:59 +0200
            Re: Thread scaling in Windows Paavo Helde <myfirstname@osa.pri.ee> - 2013-06-01 03:06 -0500
              Re: Thread scaling in Windows Marcel Müller <news.5.maazl@spamgourmet.org> - 2013-06-01 15:20 +0200
                Re: Thread scaling in Windows Drazen Kacar <dave@fly.srk.fer.hr> - 2013-06-02 06:35 +0000
            Re: Thread scaling in Windows Casper H.S. Dik <Casper.Dik@OrSPaMcle.COM> - 2013-06-01 12:34 +0000
              Re: Thread scaling in Windows Marcel Müller <news.5.maazl@spamgourmet.org> - 2013-06-01 15:09 +0200
                Re: Thread scaling in Windows Casper H.S. Dik <Casper.Dik@OrSPaMcle.COM> - 2013-06-01 17:12 +0000

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