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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 <sjitindarsingh@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This commit is contained in:
Suraj Jitindar Singh 2016-10-14 11:53:22 +11:00 committed by Paul Mackerras
parent e03f3921e5
commit f4944613ad
1 changed files with 1 additions and 1 deletions
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2
arch/powerpc/include/asm/kvm_host.h
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@ -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