linux-kernel - Re: [RFC PATCH 3/3] kvm: use yield_to instead of sleep in kvm_vcpu_on

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Message-ID: <4D010CD4.4020400@redhat.com>
Date:	Thu, 09 Dec 2010 12:07:32 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Avi Kivity <avi@...hat.com>
CC:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>,
	Anthony Liguori <aliguori@...ux.vnet.ibm.com>
Subject: Re: [RFC PATCH 3/3] kvm: use yield_to instead of sleep in kvm_vcpu_on_spin

On 12/09/2010 05:28 AM, Avi Kivity wrote:
> On 12/09/2010 12:38 AM, Rik van Riel wrote:
>>
>>>> - /* Sleep for 100 us, and hope lock-holder got scheduled */
>>>> - expires = ktime_add_ns(ktime_get(), 100000UL);
>>>> - schedule_hrtimeout(&expires, HRTIMER_MODE_ABS);
>>>> + if (first_round&& last_boosted_vcpu == kvm->last_boosted_vcpu) {
>>>> + /* We have not found anyone yet. */
>>>> + first_round = 0;
>>>> + goto again;
>>>
>>> Need to guarantee termination.
>>
>> We do that by setting first_round to 0 :)
>>
>> We at most walk N+1 VCPUs in a VM with N VCPUs, with
>> this patch.
>>
>
> Right. May be clearer by using a for () loop instead of the goto.

And open coding kvm_for_each_vcpu ?

Somehow I suspect that won't add to clarity...

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