From: Rik van Riel <riel@redhat.com>
To: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Marcelo Tosatti <mtosatti@redhat.com>,
Ingo Molnar <mingo@redhat.com>, Avi Kivity <avi@redhat.com>,
S390 <linux-s390@vger.kernel.org>,
Carsten Otte <cotte@de.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
KVM <kvm@vger.kernel.org>, chegu vinod <chegu_vinod@hp.com>,
"Andrew M. Theurer" <habanero@linux.vnet.ibm.com>,
LKML <linux-kernel@vger.kernel.org>, X86 <x86@kernel.org>,
Gleb Natapov <gleb@redhat.com>,
linux390@de.ibm.com,
Srivatsa Vaddagiri <srivatsa.vaddagiri@gmail.com>,
Joerg Roedel <joerg.roedel@amd.com>
Subject: Re: [PATCH RFC 0/2] kvm: Improving directed yield in PLE handler
Date: Mon, 09 Jul 2012 18:28:03 -0400 [thread overview]
Message-ID: <4FFB5AF3.4010805@redhat.com> (raw)
In-Reply-To: <20120709062012.24030.37154.sendpatchset@codeblue>
On 07/09/2012 02:20 AM, Raghavendra K T wrote:
> Currently Pause Looop Exit (PLE) handler is doing directed yield to a
> random VCPU on PL exit. Though we already have filtering while choosing
> the candidate to yield_to, we can do better.
>
> Problem is, for large vcpu guests, we have more probability of yielding
> to a bad vcpu. We are not able to prevent directed yield to same guy who
> has done PL exit recently, who perhaps spins again and wastes CPU.
>
> Fix that by keeping track of who has done PL exit. So The Algorithm in series
> give chance to a VCPU which has:
>
> (a) Not done PLE exit at all (probably he is preempted lock-holder)
>
> (b) VCPU skipped in last iteration because it did PL exit, and probably
> has become eligible now (next eligible lock holder)
>
> Future enhancemnets:
Your patch series looks good to me. Simple changes with a
significant result.
However, the simple heuristic could use some comments :)
--
All rights reversed
prev parent reply other threads:[~2012-07-09 22:28 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-09 6:20 [PATCH RFC 0/2] kvm: Improving directed yield in PLE handler Raghavendra K T
2012-07-09 6:20 ` [PATCH RFC 1/2] kvm vcpu: Note down pause loop exit Raghavendra K T
2012-07-09 6:33 ` Raghavendra K T
2012-07-09 22:39 ` Rik van Riel
2012-07-10 11:22 ` Raghavendra K T
2012-07-11 8:53 ` Avi Kivity
2012-07-11 10:52 ` Raghavendra K T
2012-07-11 11:18 ` Avi Kivity
2012-07-11 11:56 ` Raghavendra K T
2012-07-11 12:41 ` Andrew Jones
2012-07-12 10:58 ` Nikunj A Dadhania
2012-07-12 11:02 ` Raghavendra K T
2012-07-09 6:20 ` [PATCH RFC 2/2] kvm PLE handler: Choose better candidate for directed yield Raghavendra K T
2012-07-09 22:30 ` Rik van Riel
2012-07-10 11:46 ` Raghavendra K T
2012-07-09 7:55 ` [PATCH RFC 0/2] kvm: Improving directed yield in PLE handler Christian Borntraeger
2012-07-10 8:27 ` Raghavendra K T
2012-07-11 9:06 ` Avi Kivity
2012-07-11 10:17 ` Christian Borntraeger
2012-07-11 11:04 ` Avi Kivity
2012-07-11 11:16 ` Alexander Graf
2012-07-11 11:23 ` Avi Kivity
2012-07-11 11:52 ` Alexander Graf
2012-07-11 12:48 ` Avi Kivity
2012-07-12 2:19 ` Benjamin Herrenschmidt
2012-07-11 11:18 ` Christian Borntraeger
2012-07-11 11:39 ` Avi Kivity
2012-07-12 5:11 ` Raghavendra K T
2012-07-12 8:11 ` Avi Kivity
2012-07-12 8:32 ` Raghavendra K T
2012-07-12 2:17 ` Benjamin Herrenschmidt
2012-07-12 8:12 ` Avi Kivity
2012-07-12 11:24 ` Benjamin Herrenschmidt
2012-07-12 10:38 ` Nikunj A Dadhania
2012-07-11 11:51 ` Raghavendra K T
2012-07-11 11:55 ` Christian Borntraeger
2012-07-11 12:04 ` Raghavendra K T
2012-07-11 13:04 ` Raghavendra K T
2012-07-09 21:47 ` Andrew Theurer
2012-07-10 9:26 ` Raghavendra K T
2012-07-10 10:07 ` [PATCH RFC 0/2] kvm: Improving directed yield in PLE handler : detailed result Raghavendra K T
2012-07-10 11:54 ` [PATCH RFC 0/2] kvm: Improving directed yield in PLE handler Raghavendra K T
2012-07-10 13:27 ` Andrew Theurer
2012-07-11 9:00 ` Avi Kivity
2012-07-11 13:59 ` Raghavendra K T
2012-07-11 14:01 ` Raghavendra K T
2012-07-12 8:15 ` Avi Kivity
2012-07-12 8:25 ` Raghavendra K T
2012-07-12 12:31 ` Avi Kivity
2012-07-09 22:28 ` Rik van Riel [this message]
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