KVM_HALT_POLL_NS_DEFAULT is an arch specific constant which sets the default value of the halt_poll_ns kvm module parameter which determines the global maximum halt polling interval.
The current value for powerpc is 500000 (500us) which means that any repetitive workload with a period of less than that can drive the cpu usage to 100% where it may have been mostly idle without halt polling. This presents the possibility of a large increase in power usage with a comparatively small performance benefit. Reduce the default to 10000 (10us) and a user can tune this themselves to set their affinity for halt polling based on the trade off between power and performance which they are willing to make. Signed-off-by: Suraj Jitindar Singh <sjitindarsi...@gmail.com> --- arch/powerpc/include/asm/kvm_host.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index 28350a2..037b6a1 100644 --- a/arch/powerpc/include/asm/kvm_host.h +++ b/arch/powerpc/include/asm/kvm_host.h @@ -48,7 +48,7 @@ #ifdef CONFIG_KVM_MMIO #define KVM_COALESCED_MMIO_PAGE_OFFSET 1 #endif -#define KVM_HALT_POLL_NS_DEFAULT 500000 +#define KVM_HALT_POLL_NS_DEFAULT 10000 /* 10 us */ /* These values are internal and can be increased later */ #define KVM_NR_IRQCHIPS 1 -- 2.5.5