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From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
To: Avi Kivity <avi@redhat.com>
Cc: habanero@linux.vnet.ibm.com, "H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Ingo Molnar <mingo@redhat.com>, Rik van Riel <riel@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>,
	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: Wed, 11 Jul 2012 19:29:42 +0530	[thread overview]
Message-ID: <4FFD86CE.9040501@linux.vnet.ibm.com> (raw)
In-Reply-To: <4FFD4091.8040804@redhat.com>

On 07/11/2012 02:30 PM, Avi Kivity wrote:
> On 07/10/2012 12:47 AM, Andrew Theurer wrote:
>>
>> For the cpu threads in the host that are actually active (in this case
>> 1/2 of them), ~50% of their time is in kernel and ~43% in guest.  This
>> is for a no-IO workload, so that's just incredible to see so much cpu
>> wasted.  I feel that 2 important areas to tackle are a more scalable
>> yield_to() and reducing the number of pause exits itself (hopefully by
>> just tuning ple_window for the latter).
>
> One thing we can do is autotune ple_window.  If a ple exit fails to wake
> anybody (because all vcpus are either running, sleeping, or in ple
> exits) then we deduce we are not overcommitted and we can increase the
> ple window.  There's the question of how to decrease it again though.
>

I see some problem here, If I interpret situation correctly. What
happens if we have two guests with one VM having no over-commit and 
other with high over-commit. (except when we have gang scheduling).

Rather we should have something tied to VM rather than rigid PLE
window.


  reply	other threads:[~2012-07-11 14:01 UTC|newest]

Thread overview: 52+ 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  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
2012-07-09 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 [this message]
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

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