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    KVM: add halt_attempted_poll to VCPU stats · 62bea5bf
    Paolo Bonzini 提交于
    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: NDavid Matlack <dmatlack@google.com>
    Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
    62bea5bf
x86.c 204.4 KB