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authorPaolo Bonzini <pbonzini@redhat.com>2015-09-15 18:27:57 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2015-09-16 12:17:00 +0200
commit62bea5bff486644ecf363fe8a1a2f6f32c614a49 (patch)
tree774180da187dabef4995896aec803248b075a36d /arch/s390
parent8f4216c7d28976f7ec1b2bcbfa0a9f787133c45e (diff)
downloadlinux-62bea5bff486644ecf363fe8a1a2f6f32c614a49.tar.gz
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>
Diffstat (limited to 'arch/s390')
-rw-r--r--arch/s390/include/asm/kvm_host.h1
-rw-r--r--arch/s390/kvm/kvm-s390.c1
2 files changed, 2 insertions, 0 deletions
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 3d012e071647..6ce4a0b7e8da 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -210,6 +210,7 @@ struct kvm_vcpu_stat {
u32 exit_validity;
u32 exit_instruction;
u32 halt_successful_poll;
+ u32 halt_attempted_poll;
u32 halt_wakeup;
u32 instruction_lctl;
u32 instruction_lctlg;
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index c91eb941b444..2f807ab1725e 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -63,6 +63,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
{ "exit_program_interruption", VCPU_STAT(exit_program_interruption) },
{ "exit_instr_and_program_int", VCPU_STAT(exit_instr_and_program) },
{ "halt_successful_poll", VCPU_STAT(halt_successful_poll) },
+ { "halt_attempted_poll", VCPU_STAT(halt_attempted_poll) },
{ "halt_wakeup", VCPU_STAT(halt_wakeup) },
{ "instruction_lctlg", VCPU_STAT(instruction_lctlg) },
{ "instruction_lctl", VCPU_STAT(instruction_lctl) },