Messages in this thread Patch in this message | | | Subject | Re: [PATCH v6 2/3] KVM: dynamic halt_poll_ns adjustment | From | Wanpeng Li <> | Date | Fri, 4 Sep 2015 09:42:10 +0800 |
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On 9/4/15 9:16 AM, Wanpeng Li 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. > > Ah, I remember why I keep poll_ns calculation in if(). Actually > poll_ns has already been accumulated into wait_ns(see how wait_ns is > calculated) if polling does not succeed. If put poll_ns calculation > before if() I need to reset variable 'start' to ktime_get().
So how about something like:
@@ -1928,7 +1962,8 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) { ktime_t start, cur; DEFINE_WAIT(wait); - bool waited = false; + bool polled = false, waited = false; + u64 poll_ns = 0, wait_ns = 0, block_ns = 0;
start = cur = ktime_get(); if (vcpu->halt_poll_ns) { @@ -1940,11 +1975,17 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) * arrives. */ if (kvm_vcpu_check_block(vcpu) < 0) { + polled = true; ++vcpu->stat.halt_successful_poll; - goto out; + break; } cur = ktime_get(); } while (single_task_running() && ktime_before(cur, stop)); + + if (polled) { + poll_ns = ktime_to_ns(cur) - ktime_to_ns(start); + goto out; + } }
Regards, Wanpeng Li
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