Messages in this thread | | | Date | Thu, 21 May 2009 11:47:22 +0300 | From | Avi Kivity <> | Subject | Re: [PATCH][KVM][retry 4] Add support for Pause Filtering to AMD SVM |
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Mark Langsdorf wrote: > 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. Perform > the reschedule by increasing the the credited time on > the VCPU. > > 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 1%. Further performance > improvement may be possible with a more sophisticated > yield algorithm. >
Please split this into a scheduler patch and a kvm patch.
-- error compiling committee.c: too many arguments to function
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