From: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
To: Avi Kivity <avi@redhat.com>
Cc: Dong Hao <haodong@linux.vnet.ibm.com>,
acme@infradead.org, mtosatti@redhat.com, mingo@elte.hu,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH v7 2/3] KVM: x86: trace mmio begin and complete
Date: Tue, 04 Sep 2012 12:06:42 +0800 [thread overview]
Message-ID: <50457E52.1070702@linux.vnet.ibm.com> (raw)
In-Reply-To: <50448F72.80702@redhat.com>
On 09/03/2012 07:07 PM, Avi Kivity wrote:
> On 08/27/2012 12:51 PM, Dong Hao wrote:
>> From: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
>>
>> 'perf kvm stat record/report' will use kvm_exit and kvm_mmio(read...) to
>> calculate mmio read emulated time for the old kernel, in order to trace
>> mmio read event more exactly, we add kvm_mmio_begin to trace the time when
>> mmio read begins, also, add kvm_io_done to trace the time when mmio/pio is
>> completed
>>
>
> Why is this so critical?
>
> If a lot of time is spent in in-kernel mmio, then 'perf top' will report
> it. Otherwise the time between kvm_exit and kvm_entry describes the
> time spent in the host. Not all of it is mmio handling, but it is quite
> close.
I have done some test, the new events can get more exact result, this is a
example in my slides:
the event handled time calculated by old events is: 0.000066(s)
calculated by new events, the result is: 0.000005(s).
So, i think it is worth introducing these new events.
But if you do not care it or think these events are duplicate with current
events or unmaintainable, i do not have strong opinion on that. Please let
me know, i will drop them in the next version.
next prev parent reply other threads:[~2012-09-04 4:06 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-27 9:51 [PATCH v7 0/3] KVM: perf: kvm events analysis tool Dong Hao
2012-08-27 9:51 ` [PATCH v7 1/3] KVM: x86: export svm/vmx exit code and vector code to userspace Dong Hao
2012-09-03 11:13 ` Avi Kivity
2012-09-04 3:53 ` Xiao Guangrong
2012-08-27 9:51 ` [PATCH v7 2/3] KVM: x86: trace mmio begin and complete Dong Hao
2012-09-03 11:07 ` Avi Kivity
2012-09-04 4:06 ` Xiao Guangrong [this message]
2012-08-27 9:51 ` [PATCH v7 3/3] KVM: perf: kvm events analysis tool Dong Hao
2012-08-27 15:53 ` Andrew Jones
2012-08-27 19:34 ` David Ahern
2012-08-28 6:35 ` Andrew Jones
2012-08-28 17:19 ` David Ahern
2012-09-02 13:51 ` don
2012-08-30 18:29 ` David Ahern
2012-09-03 8:48 ` don
2012-09-03 16:04 ` David Ahern
2012-09-13 4:56 ` David Ahern
2012-09-13 13:45 ` Arnaldo Carvalho de Melo
2012-09-13 14:14 ` David Ahern
2012-09-13 14:31 ` Arnaldo Carvalho de Melo
2012-09-14 2:56 ` Xiao Guangrong
2012-09-14 11:51 ` David Ahern
2012-08-27 9:59 ` [PATCH v7 0/3] " Xiao Guangrong
2012-08-27 12:53 ` David Ahern
-- strict thread matches above, loose matches on Subject: below --
2012-08-24 1:15 Dong Hao
2012-08-24 1:15 ` [PATCH v7 2/3] KVM: x86: trace mmio begin and complete Dong Hao
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