Message-ID: <4D010CD4.4020400@redhat.com>
Date: Thu, 09 Dec 2010 12:07:32 -0500
From: Rik van Riel <riel@redhat.com>
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To: Avi Kivity <avi@redhat.com>
CC: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>, Ingo Molnar <mingo@elte.hu>,
        Anthony Liguori <aliguori@linux.vnet.ibm.com>
Subject: Re: [RFC PATCH 3/3] kvm: use yield_to instead of sleep in kvm_vcpu_on_spin
References: <20101202144129.4357fe00@annuminas.surriel.com> <20101202144516.45a0385d@annuminas.surriel.com> <4CFB8BFA.4040100@redhat.com> <4D0008D5.1040102@redhat.com> <4D00AF3C.40603@redhat.com>
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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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