Date: Fri, 4 Jun 2004 16:30:28 -0400 (EDT) From: Robert Watson <rwatson@freebsd.org> To: Steven Hartland <killing@multiplay.co.uk> Cc: Ali Niknam <ali@transip.nl> Subject: Re: FreeBSD 5.2.1: Mutex/Spinlock starvation? Message-ID: <Pine.NEB.3.96L.1040604162906.34555P-100000@fledge.watson.org> In-Reply-To: <00fb01c44a71$c7f26d10$b3db87d4@multiplay.co.uk>
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On Fri, 4 Jun 2004, Steven Hartland wrote: > > You might want to try adding "options ADAPTIVE_MUTEXES" to your kernel > > configuration, which will cause mutexes to spin briefly on SMP systems > > before sleeping, and has been observed to improve performance quite a bit. > > Thats very interesting is there a specific set off conditions where it > would pay off that you guys know of or is it more a try it and see? > > We run ~ 100 dual machines here the vast majority FreeBSD as game > servers and would consider upgrading the kernels if you thought it would > help. Well, I know a bit about the general conditions -- situations where mutexes are held for short periods of time, rather than over long transactions. I know from experience that adaptive mutexes can make an observable difference for system builds and IPC activities. To what extent do you have systems where you can reproduce your production load without impacting production quality? I may have some interesting patches for you to try running with, if so :-). Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Senior Research Scientist, McAfee Research
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