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| author | Paolo Bonzini <pbonzini@redhat.com> | 2015-09-15 18:27:57 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2015-09-16 12:17:00 +0200 |
| commit | 62bea5bff486644ecf363fe8a1a2f6f32c614a49 (patch) | |
| tree | 774180da187dabef4995896aec803248b075a36d /arch/s390 | |
| parent | 8f4216c7d28976f7ec1b2bcbfa0a9f787133c45e (diff) | |
| download | linux-62bea5bff486644ecf363fe8a1a2f6f32c614a49.tar.bz2 | |
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.h | 1 | ||||
| -rw-r--r-- | arch/s390/kvm/kvm-s390.c | 1 |
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) }, |