From: Suraj Jitindar Singh Date: Fri, 14 Oct 2016 00:53:22 +0000 (+1100) Subject: KVM: PPC: Decrease the powerpc default halt poll max value X-Git-Tag: v4.10-rc1~139^2~18^2~2 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=f4944613ad1ab6760589d5791488be1236c07fcc;p=linux.git KVM: PPC: Decrease the powerpc default halt poll max value 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 Signed-off-by: Paul Mackerras --- diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index f15713ae3f34..e59b172666cd 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