Date: Mon, 30 Jun 2008 19:21:54 -0400 From: alex@schnarff.com To: questions@freebsd.org Subject: Re: Too Much Context Switching? Message-ID: <20080630192154.nj1sns26kg44w4w8@mail.schnarff.com> In-Reply-To: <48692DE7.3020502@FreeBSD.org> References: <20080630165205.GA3033@lpthe.jussieu.fr> <48691D7C.2090804@FreeBSD.org> <20080630181755.GA3327@lpthe.jussieu.fr> <48692DE7.3020502@FreeBSD.org>
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Quoting Kris Kennaway <kris@FreeBSD.org>: > Michel Talon wrote: >> On Mon, Jun 30, 2008 at 07:53:00PM +0200, Kris Kennaway wrote: >>> Yep, it could be that -- what confuses me though is that it is >>> claimed that performance suddenly regressed. If so then this >>> cannot be the underlying cause. >> >> It may be that the load has augmented to the point that contention >> imposes a rapid regression on throughput. > > Yes, it could be that. I don't know off-hand whether multiple threads > are counted separately by vmstat (at a guess I'd say no), but ps/top/etc > should show how many are active in the python process. Just ran ktrace, and a bit of Googling seems to confirm my initial suspicion that the results I'm seeing are abnormal. The first several screenfulls of output look like this: 52929 python2.4 1214867016.469416 CALL kse_wakeup(0x811740c) 52929 python2.4 0.000060 RET kse_wakeup 0 52929 python2.4 0.000008 RET kse_release 0 52929 python2.4 0.000040 CALL kse_release(0x811df4c) 52929 python2.4 0.000515 CALL kse_wakeup(0x811740c) 52929 python2.4 0.000012 RET kse_wakeup 0 52929 python2.4 0.000004 RET kse_release 0 52929 python2.4 0.000012 CALL kse_release(0x811df4c) 52929 python2.4 0.000365 CALL kse_wakeup(0x811740c) 52929 python2.4 0.000012 RET kse_wakeup 0 52929 python2.4 0.000003 RET kse_release 0 52929 python2.4 0.000010 CALL kse_release(0x811df4c) 52929 python2.4 0.000413 CALL kse_wakeup(0x811740c) 52929 python2.4 0.000011 RET kse_wakeup 0 52929 python2.4 0.000004 RET kse_release 0 52929 python2.4 0.000009 CALL kse_release(0x811df4c) 52929 python2.4 0.000393 CALL kse_wakeup(0x811740c) 52929 python2.4 0.000012 RET kse_wakeup 0 52929 python2.4 0.000004 RET kse_release 0 52929 python2.4 0.000009 CALL kse_release(0x811df4c) I may be mistaken, but it seems like that's a lot of unnecessary activity managing the threads; the confirmation I found came from http://arkiv.freebsd.se/?ml=freebsd-threads&a=2007-02&t=3178634. Am I correct that this is abnormal behavior? If so, any idea what I may need to do to fix the issue? Alex
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