Date: Mon, 30 Jun 2008 20:20:34 -0400 From: alex@schnarff.com To: questions@freebsd.org Subject: Re: Too Much Context Switching? - FIXED Message-ID: <20080630202034.dt6mqbf5css444gg@mail.schnarff.com> In-Reply-To: <48697719.40101@FreeBSD.org> References: <20080630165205.GA3033@lpthe.jussieu.fr> <48691D7C.2090804@FreeBSD.org> <20080630181755.GA3327@lpthe.jussieu.fr> <48692DE7.3020502@FreeBSD.org> <20080630192154.nj1sns26kg44w4w8@mail.schnarff.com> <48696EB0.6000906@FreeBSD.org> <20080630200456.uf01ro1obms40cok@mail.schnarff.com> <48697719.40101@FreeBSD.org>
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Quoting Kris Kennaway <kris@FreeBSD.org>: > alex@schnarff.com wrote: >> Quoting Kris Kennaway <kris@FreeBSD.org>: >> >>> 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. >> >> WOW...it's *amazing* how much of a difference a single sysctl can make. >> >> I went ahead and set kern.threads.virtual_cpu=1, as suggested in the >> thread above, and the difference is ridiculous -- Zope is now faster >> than I've ever seen. More importantly, my ktracing shows that all of >> the kse_* garabage is now gone. >> >> I'll probably be upgrading to 7.0 in the next month or so, given >> that this is obviously a thread issue and that that release has much >> improved thread code. However, for the time being, the pressing >> issue is fixed, and for anyone in my position stuck on 6.2...this is >> night & day. > > Seriously, try libthr. No matter what you do to libkse it is going to > suck. That's why we removed it. I will, probably as part of upgrading to 7.0 (which I may accelerate, given this point). I'm just ecstatic at the difference I'm already seeing, and specifically wanted to make note of it in the archives. Point very much taken, though. :-) Alex
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