From 62bea5bff486644ecf363fe8a1a2f6f32c614a49 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Tue, 15 Sep 2015 18:27:57 +0200 Subject: KVM: add halt_attempted_poll to VCPU stats This new statistic can help diagnosing VCPUs that, for any reason, trigger bad behavior of halt_poll_ns autotuning. For example, say halt_poll_ns = 480000, and wakeups are spaced exactly like 479us, 481us, 479us, 481us. Then KVM always fails polling and wastes 10+20+40+80+160+320+480 = 1110 microseconds out of every 479+481+479+481+479+481+479 = 3359 microseconds. The VCPU then is consuming about 30% more CPU than it would use without polling. This would show as an abnormally high number of attempted polling compared to the successful polls. Acked-by: Christian Borntraeger Signed-off-by: Paolo Bonzini --- arch/mips/include/asm/kvm_host.h | 1 + arch/mips/kvm/mips.c | 1 + 2 files changed, 2 insertions(+) (limited to 'arch/mips') diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h index e8c8d9d0c45f..3a54dbca9f7e 100644 --- a/arch/mips/include/asm/kvm_host.h +++ b/arch/mips/include/asm/kvm_host.h @@ -128,6 +128,7 @@ struct kvm_vcpu_stat { u32 msa_disabled_exits; u32 flush_dcache_exits; u32 halt_successful_poll; + u32 halt_attempted_poll; u32 halt_wakeup; }; diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index cd4c129ce743..49ff3bfc007e 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -55,6 +55,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = { { "msa_disabled", VCPU_STAT(msa_disabled_exits), KVM_STAT_VCPU }, { "flush_dcache", VCPU_STAT(flush_dcache_exits), KVM_STAT_VCPU }, { "halt_successful_poll", VCPU_STAT(halt_successful_poll), KVM_STAT_VCPU }, + { "halt_attempted_poll", VCPU_STAT(halt_attempted_poll), KVM_STAT_VCPU }, { "halt_wakeup", VCPU_STAT(halt_wakeup), KVM_STAT_VCPU }, {NULL} }; -- cgit v1.2.3