linux-kernel - Re: [PATCH v2 2/3] KVM: x86: add tracepoints to trace mmio begin and complete

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Date:	Thu, 02 Feb 2012 19:56:22 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong.eric@...il.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Stefan Hajnoczi <stefanha@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] KVM: x86: add tracepoints to trace mmio begin
 and complete

On 02/02/2012 07:55 PM, Xiao Guangrong wrote:
> On 02/03/2012 01:36 AM, Avi Kivity wrote:
>
> > On 02/02/2012 07:27 PM, Xiao Guangrong wrote:
> >> From: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
> >>
> >> 'perf kvm-events' 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_mmio_done to trace the time when mmio/pio is completed
> > 
> > Previously, we discussed using the kvm_entry to do this.  This reduces
> > the number of tracepoints, and is backwards compatible.  What was the
> > conclusion?
> > 
>
>
> Since using kvm_entry can cause lots of unnecessary calculated, these new two
> tracepoints can let the result be exacter.

Do you have numbers on the ratio between kvm_entry traces and
kvm_mmio_begin/end traces?

> And, they are only used in new kernel, we will fall back to using kvm_entry if
> they are not existing, that means it does not break backwards compatible.

Ah ok.


-- 
error compiling committee.c: too many arguments to function

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