From: Avi Kivity <avi@redhat.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: "Zhai, Edwin" <edwin.zhai@intel.com>, Ingo Molnar <mingo@elte.hu>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH] [RESEND] KVM:VMX: Add support for Pause-Loop Exiting
Date: Sun, 27 Sep 2009 10:31:21 +0200 [thread overview]
Message-ID: <4ABF22D9.3040308@redhat.com> (raw)
In-Reply-To: <20090925204339.GA29634@8bytes.org>
On 09/25/2009 11:43 PM, Joerg Roedel wrote:
> On Wed, Sep 23, 2009 at 05:09:38PM +0300, Avi Kivity wrote:
>
>> We haven't sorted out what is the correct thing to do here. I think we
>> should go for a directed yield, but until we have it, you can use
>> hrtimers to sleep for 100 microseconds and hope the holding vcpu will
>> get scheduled. Even if it doesn't, we're only wasting a few percent cpu
>> time instead of spinning.
>>
> How do you plan to find out to which vcpu thread the current thread
> should yield?
>
We can't find exactly which vcpu, but we can:
- rule out threads that are not vcpus for this guest
- rule out threads that are already running
A major problem with sleep() is that it effectively reduces the vm
priority relative to guests that don't have spinlock contention. By
selecting a random nonrunnable vcpu belonging to this guest, we at least
preserve the guest's timeslice.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
next prev parent reply other threads:[~2009-09-27 8:31 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-23 14:04 [PATCH] [RESEND] KVM:VMX: Add support for Pause-Loop Exiting Zhai, Edwin
2009-09-23 14:09 ` Avi Kivity
2009-09-25 1:11 ` Zhai, Edwin
2009-09-27 8:28 ` Avi Kivity
2009-09-28 9:33 ` Zhai, Edwin
2009-09-29 12:05 ` Zhai, Edwin
2009-09-29 13:34 ` Avi Kivity
2009-09-30 1:01 ` Zhai, Edwin
2009-09-30 6:28 ` Avi Kivity
2009-09-30 16:22 ` Marcelo Tosatti
2009-10-02 18:28 ` Marcelo Tosatti
2009-10-09 10:03 ` Zhai, Edwin
2009-10-11 15:34 ` Avi Kivity
2009-10-12 19:13 ` Marcelo Tosatti
2009-09-25 20:43 ` Joerg Roedel
2009-09-27 8:31 ` Avi Kivity [this message]
2009-09-27 13:46 ` Joerg Roedel
2009-09-27 13:47 ` Avi Kivity
2009-09-27 14:07 ` Joerg Roedel
2009-09-27 14:18 ` Avi Kivity
2009-09-27 14:53 ` Joerg Roedel
2009-09-29 16:46 ` Avi Kivity
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