On Tue, Oct 06, 2009 at 02:25:02PM -0500, Mark Langsdorf wrote: > >From 8ec340648103510095ff339b914706c81e9d815d Mon Sep 17 00:00:00 2001 > From: Mark Langsdorf <mark.langsdorf@xxxxxxx> > Date: Wed, 9 Sep 2009 22:12:51 -0500 > Subject: [PATCH] [PATCH] Support Pause Filter in AMD processors > > New AMD processors (Family 0x10 models 8+) support the Pause > Filter Feature. This feature creates a new field in the VMCB > called Pause Filter Count. If Pause Filter Count is greater > than 0 and intercepting PAUSEs is enabled, the processor will > increment an internal counter when a PAUSE instruction occurs > instead of intercepting. When the internal counter reaches the > Pause Filter Count value, a PAUSE intercept will occur. > > This feature can be used to detect contended spinlocks, > especially when the lock holding VCPU is not scheduled. > Rescheduling another VCPU prevents the VCPU seeking the > lock from wasting its quantum by spinning idly. > > Experimental results show that most spinlocks are held > for less than 1000 PAUSE cycles or more than a few > thousand. Default the Pause Filter Counter to 3000 to > detect the contended spinlocks. > > Processor support for this feature is indicated by a CPUID > bit. > > On a 24 core system running 4 guests each with 16 VCPUs, > this patch improved overall performance of each guest's > 32 job kernbench by approximately 3-5% when combined > with a scheduler algorithm thati caused the VCPU to > sleep for a brief period. Further performance improvement > may be possible with a more sophisticated yield algorithm. > > This patch depends on the changes to the kvm code from > "KVM:VMX: Add support for Pause Loop Exiting" > http://www.mail-archive.com/kvm@xxxxxxxxxxxxxxx/msg23089.html > > -Mark Langsdorf > Operating System Research Center > AMD > > Signed-of-by: Mark Langsdorf <mark.langsdorf@xxxxxxx> Applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
