Date: Tue, 01 Jul 2008 01:39:28 +0200 From: Kris Kennaway <kris@FreeBSD.org> To: alex@schnarff.com Cc: questions@freebsd.org Subject: Re: Too Much Context Switching? Message-ID: <48696EB0.6000906@FreeBSD.org> In-Reply-To: <20080630192154.nj1sns26kg44w4w8@mail.schnarff.com> References: <20080630165205.GA3033@lpthe.jussieu.fr> <48691D7C.2090804@FreeBSD.org> <20080630181755.GA3327@lpthe.jussieu.fr> <48692DE7.3020502@FreeBSD.org> <20080630192154.nj1sns26kg44w4w8@mail.schnarff.com>
next in thread | previous in thread | raw e-mail | index | archive | help
alex@schnarff.com wrote: > 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? Looks exactly like the python thread problem Michel described. You will get some improvement by switching to libthr and/or updating to 7.0 as I discussed, but ultimately you're hitting limits of python, not FreeBSD. Kris
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?48696EB0.6000906>