linux-kernel - Re: [PATCH 3/3] KVM: perf: kvm events analysis tool

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Message-ID: <4F432475.4090903@gmail.com>
Date:	Mon, 20 Feb 2012 21:58:29 -0700
From:	David Ahern <dsahern@...il.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
CC:	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Avi Kivity <avi@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH 3/3] KVM: perf: kvm events analysis tool

On 2/20/12 8:52 PM, Xiao Guangrong wrote:
>>> +    /* Both begin and end events did not get the key. */
>>> +    if (!event&&   key->key == INVALID_KEY)
>>> +        return;
>>> +
>> Should not be able to get here with event unset, so the next 2 lines should not be needed. ie., you only want to process events where the begin event was seen in which case event is defined.
>
>
> In some case, the 'begin event' just records the start timestamp, the actually event
> is recognised in the 'end event'.
>
> Take mmio-read for example, in the old kernel, we use kvm-exit as the 'begin event'
> and kvm_mmio(KVM_TRACE_MMIO_READ...) is the 'end event'.

ah, ok. Please add a comment about this path.

David

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