From: Jes Sorensen <Jes.Sorensen@redhat.com>
To: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Cc: Avi Kivity <avi@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
kvm@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Fr??d??ric Weisbecker <fweisbec@gmail.com>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Lin Ming <ming.m.lin@intel.com>,
Sheng Yang <sheng@linux.intel.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
oerg Roedel <joro@8bytes.org>, Gleb Natapov <gleb@redhat.com>,
Zachary Amsden <zamsden@redhat.com>,
zhiteng.huang@intel.com, tim.c.chen@intel.com,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH V2 1/5] ara virt interface of perf to support kvm guest os statistics collection in guest os
Date: Wed, 23 Jun 2010 10:15:23 +0200 [thread overview]
Message-ID: <4C21C29B.70902@redhat.com> (raw)
In-Reply-To: <1277255624.2096.728.camel@ymzhang.sh.intel.com>
On 06/23/10 03:13, Zhang, Yanmin wrote:
> On Tue, 2010-06-22 at 09:58 +0200, Jes Sorensen wrote:
>> Exposing the counters read-only would save a lot of overhead for sure.
>>>> Question is if it is safe to drop overflow support?
>>> Not safe. One of PMU hardware design objectives is to use interrupt or NMI to notify
>>> software when event counter overflows. Without overflow support, software need poll
>>> the PMU registers looply. That is not good and consumes more cpu resources.
>>
>> Here is an idea, how about having the overflow NMI in the host trigger a
>> flag that causes the PMU register read to trap and get special handling?
>> That way you could propagate the overflow back down to the guest.
> That doesn't resolve the issue that guest os software has to poll register.
That is true, but it could set a flag through the para virt interface.
Cheers,
Jes
next prev parent reply other threads:[~2010-06-23 8:15 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-21 9:31 [PATCH V2 1/5] ara virt interface of perf to support kvm guest os statistics collection in guest os Zhang, Yanmin
2010-06-21 11:45 ` Avi Kivity
2010-06-22 1:49 ` Zhang, Yanmin
2010-06-22 7:14 ` Jes Sorensen
2010-06-22 7:47 ` Zhang, Yanmin
2010-06-22 7:55 ` Peter Zijlstra
2010-06-22 8:00 ` Jes Sorensen
2010-06-22 9:29 ` Zhang, Yanmin
2010-06-22 9:31 ` Peter Zijlstra
2010-06-22 9:39 ` Jes Sorensen
2010-06-22 9:46 ` Peter Zijlstra
2010-06-22 9:53 ` Avi Kivity
2010-06-22 10:02 ` Peter Zijlstra
2010-06-22 10:06 ` Avi Kivity
2010-06-22 10:10 ` Peter Zijlstra
2010-06-22 11:01 ` Avi Kivity
2010-06-22 7:58 ` Jes Sorensen
2010-06-23 1:13 ` Zhang, Yanmin
2010-06-23 8:15 ` Jes Sorensen [this message]
2010-06-22 8:59 ` Avi Kivity
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