Messages in this thread Patch in this message | | | From | Wanpeng Li <> | Subject | Re: [PATCH v6 2/3] KVM: dynamic halt_poll_ns adjustment | Date | Thu, 3 Sep 2015 17:23:39 +0800 |
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On 9/3/15 2:09 AM, David Matlack wrote: [...] >> + >> static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu) >> { >> if (kvm_arch_vcpu_runnable(vcpu)) { >> @@ -1929,6 +1963,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) >> ktime_t start, cur; >> DEFINE_WAIT(wait); >> bool waited = false; >> + u64 poll_ns = 0, wait_ns = 0, block_ns = 0; >> >> start = cur = ktime_get(); >> if (vcpu->halt_poll_ns) { >> @@ -1941,10 +1976,15 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) >> */ >> if (kvm_vcpu_check_block(vcpu) < 0) { >> ++vcpu->stat.halt_successful_poll; >> - goto out; >> + break; >> } >> cur = ktime_get(); >> } while (single_task_running() && ktime_before(cur, stop)); >> + >> + if (ktime_before(cur, stop)) { > You can't use 'cur' to tell if the interrupt arrived. single_task_running() > can break us out of the loop before 'stop'. > >> + poll_ns = ktime_to_ns(cur) - ktime_to_ns(start); > Put this line before the if(). block_ns should always include the time > spent polling; even if polling does not succeed.
How about something like:
@@ -1941,10 +1976,14 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) */ if (kvm_vcpu_check_block(vcpu) < 0) { ++vcpu->stat.halt_successful_poll; - goto out; + break; } cur = ktime_get(); } while (single_task_running() && ktime_before(cur, stop)); + + poll_ns = ktime_to_ns(cur) - ktime_to_ns(start); + if (ktime_before(cur, stop) && single_task_running()) + goto out; }
> >> + goto out; >> + } >> } >> >> for (;;) { >> @@ -1959,9 +1999,24 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) >> >> finish_wait(&vcpu->wq, &wait); >> cur = ktime_get(); >> + wait_ns = ktime_to_ns(cur) - ktime_to_ns(start); >> >> out: >> - trace_kvm_vcpu_wakeup(ktime_to_ns(cur) - ktime_to_ns(start), waited); >> + block_ns = poll_ns + wait_ns; >> + >> + if (halt_poll_ns) { > If you want, you can leave this if() out and save some indentation.
Then we will miss the tracepoint.
Regards, Wanpeng Li
> >> + if (block_ns <= vcpu->halt_poll_ns) >> + ; >> + /* we had a long block, shrink polling */ >> + else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns) >> + shrink_halt_poll_ns(vcpu); >> + /* we had a short halt and our poll time is too small */ >> + else if (vcpu->halt_poll_ns < halt_poll_ns && >> + block_ns < halt_poll_ns) >> + grow_halt_poll_ns(vcpu); >> + } >> + >> + trace_kvm_vcpu_wakeup(block_ns, waited); >> } >> EXPORT_SYMBOL_GPL(kvm_vcpu_block); >> >> -- >> 1.9.1 >>
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