Date: Wed, 24 Oct 2012 14:43:25 -0400 From: John Baldwin <jhb@freebsd.org> To: Jim Harris <jimharris@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r242014 - head/sys/kern Message-ID: <201210241443.25988.jhb@freebsd.org> In-Reply-To: <201210241836.q9OIafqo073002@svn.freebsd.org> References: <201210241836.q9OIafqo073002@svn.freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Wednesday, October 24, 2012 2:36:41 pm Jim Harris wrote: > Author: jimharris > Date: Wed Oct 24 18:36:41 2012 > New Revision: 242014 > URL: http://svn.freebsd.org/changeset/base/242014 > > Log: > Pad tdq_lock to avoid false sharing with tdq_load and tdq_cpu_idle. > > This enables CPU searches (which read tdq_load) to operate independently > of any contention on the spinlock. Some scheduler-intensive workloads > running on an 8C single-socket SNB Xeon show considerable improvement with > this change (2-3% perf improvement, 5-6% decrease in CPU util). > > Sponsored by: Intel > Reviewed by: jeff > > Modified: > head/sys/kern/sched_ule.c > > Modified: head/sys/kern/sched_ule.c > ============================================================================== > --- head/sys/kern/sched_ule.c Wed Oct 24 18:33:44 2012 (r242013) > +++ head/sys/kern/sched_ule.c Wed Oct 24 18:36:41 2012 (r242014) > @@ -223,8 +223,13 @@ static int sched_idlespinthresh = -1; > * locking in sched_pickcpu(); > */ > struct tdq { > - /* Ordered to improve efficiency of cpu_search() and switch(). */ > + /* > + * Ordered to improve efficiency of cpu_search() and switch(). > + * tdq_lock is padded to avoid false sharing with tdq_load and > + * tdq_cpu_idle. > + */ > struct mtx tdq_lock; /* run queue lock. */ > + char pad[64 - sizeof(struct mtx)]; Can this use 'tdq_lock __aligned(CACHE_LINE_SIZE)' instead? -- John Baldwin
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201210241443.25988.jhb>