On 10/08/2013 11:08 PM, Marc Zyngier wrote:
This is a respin of a patch I posted a long while ago, this time with
numbers that I hope to be convincing enough.
The basic idea is that spinning on WFE in a guest is a waste of
resource, and that we're better of running another vcpu instead. This
specially shows when the system is oversubscribed. The guest vcpus can
be seen spinning, waiting for a lock to be released while the lock
holder is nowhere near a physical CPU.
This patch series just enables WFE trapping on both ARM and arm64, and
calls kvm_vcpu_on_spin(). This is enough to boost other vcpus, and
dramatically reduce the overhead.
Branch available at:
git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git
kvm-arm64/wfe-trap
Changes from v1:
- Added CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT, as it seems to give
slightly better results (Thanks to Raghavendra K T)
- Updated commit message with results of 8x configuration
Marc Zyngier (2):
ARM: KVM: Yield CPU when vcpu executes a WFE
arm64: KVM: Yield CPU when vcpu executes a WFE
Using PLE handler and enabling CPU_RELAX_INTERCEPT part of the patches
looks fine.
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