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 <borntraeger@de.ibm.com<
Reviewed-by: David Matlack <dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index dcba0fa5176e990f8a23333f08e34e192351b407..687ddeba36117ac26ec2e8d5368daaed8b0158e2 100644 (file)
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -148,6 +148,7 @@ struct kvm_vm_stat {
 
 struct kvm_vcpu_stat {
        u32 halt_successful_poll;
+       u32 halt_attempted_poll;
        u32 halt_wakeup;
 };
 

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 415938dc45cff94600625963b71011882f3a3ae4..486594583cc62c7b739f87cb7feba915e2ca53f0 100644 (file)
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -195,6 +195,7 @@ struct kvm_vm_stat {
 
 struct kvm_vcpu_stat {
        u32 halt_successful_poll;
+       u32 halt_attempted_poll;
        u32 halt_wakeup;
 };
 

diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index e8c8d9d0c45fe7c3600ba39a44e7090ba0827a04..3a54dbca9f7e0b9d0ab11d0a65aad59ddb9bc29b 100644 (file)
--- 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 cd4c129ce7434d60fc6af74bb6b764b536de4dda..49ff3bfc007e534529d0f61d21b6fddd6578d145 100644 (file)
--- 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}
 };

diff --cc arch/powerpc/include/asm/kvm_host.h
Simple merge

diff --cc arch/powerpc/kvm/book3s.c
Simple merge

diff --cc arch/powerpc/kvm/booke.c
Simple merge

diff --cc arch/s390/include/asm/kvm_host.h
Simple merge

diff --cc arch/s390/kvm/kvm-s390.c
Simple merge

diff --cc arch/x86/include/asm/kvm_host.h
Simple merge

diff --cc arch/x86/kvm/x86.c
Simple merge

diff --cc virt/kvm/kvm_main.c
Simple merge