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

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Message-ID: <55E7F75B.2030502@redhat.com>
Date:	Thu, 3 Sep 2015 09:31:39 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	David Matlack <dmatlack@...gle.com>
Cc:	Wanpeng Li <wanpeng.li@...mail.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 02/09/2015 21:23, David Matlack wrote:
> 
> I actually wasn't thinking about vcpu->halt_poll_ns though. If
> single_task_running() breaks us out of the loop we will "goto out" instead
> of scheduling. My suspicion is this will cause us to loop calling
> kvm_vcpu_block and starve the waiting task (at least until need_resched()),
> which would break the "only hog the cpu when idle" aspect of halt-polling.

That's definitely a bug, yes.

Paolo
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