linux-kernel - Re: [PATCH v6 2/3] KVM: dynamic halt_poll

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Date:	Thu, 3 Sep 2015 09:07:39 -0700
From:	David Matlack <dmatlack@...gle.com>
To:	Wanpeng Li <wanpeng.li@...mail.com>
Cc:	Paolo Bonzini <pbonzini@...hat.com>,
	kvm list <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 2/3] KVM: dynamic halt_poll_ns adjustment

On Thu, Sep 3, 2015 at 2:23 AM, Wanpeng Li <wanpeng.li@...mail.com> wrote:
>
> 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;

I would prefer an explicit signal (e.g. set a bool to true before breaking out
of the loop, and check it here) to avoid duplicating the loop exit condition.
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