From: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
To: David Ahern <dsahern@gmail.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
Avi Kivity <avi@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH 2/3] KVM: improve trace events of vmexit/mmio/ioport
Date: Wed, 18 Jan 2012 10:32:08 +0800 [thread overview]
Message-ID: <4F162F28.4010001@linux.vnet.ibm.com> (raw)
In-Reply-To: <4F15B08D.5090000@gmail.com>
On 01/18/2012 01:31 AM, David Ahern wrote:
>>>>
>>>> Relying on the existing tracepoints will make the tool work on older
>>>> kernels.
>>>>
>>>
>>>
>>> We can drop all new events, but unfortunately, the information of the origin
>>> tracepoints is not enough, at least vcpu_id need be traced in theses events
>>> to match its events. Yes?
>>
>> Yes, and if you don't add completed events, you'll have to use kvm_entry
>> whose collection adds a lot of overhead.
>
>
> vcpus run as threads and hence have their own tid which is available in
> the perf samples.
>
Nice, thanks for your information, David!
> There is an ongoing 'discussion' about modifying existing tracepoints
> which your proposed patch violates. This is the start of it:
>
Hmm, i think we can still add completed tracepoints in the new version kernel,
if old version kernel is used, we can fall back to use kvm_entry instead?
And there is a exception for mmio read, in current code, the mmio read event is
actually used to trace the time when then read emulation is completed, i think
we can add a tracepoint like mmio_read_begin to trace the start time of mmio read.
So:
- for the new kernel, we use mmio_read_begion and kvm_mmio(READ...) to calculate
start time and end time.
- for the old kernel, we use kvm_exit and kvm_mmio(READ...) to calculate start time
and end time.
Your idea?
next prev parent reply other threads:[~2012-01-18 2:32 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-16 9:30 [RFC][PATCH] KVM: perf: a smart tool to analyse kvm events Xiao Guangrong
2012-01-16 9:31 ` [PATCH 1/3] KVM: trace mmio read event properly Xiao Guangrong
2012-01-16 10:18 ` Avi Kivity
2012-01-17 2:36 ` Xiao Guangrong
2012-01-16 9:32 ` [PATCH 2/3] KVM: improve trace events of vmexit/mmio/ioport Xiao Guangrong
2012-01-16 9:38 ` Avi Kivity
2012-01-17 2:28 ` Xiao Guangrong
2012-01-17 11:55 ` Marcelo Tosatti
2012-01-17 17:31 ` David Ahern
2012-01-18 2:32 ` Xiao Guangrong [this message]
2012-01-18 5:34 ` David Ahern
2012-01-24 12:44 ` Avi Kivity
2012-01-16 9:32 ` [PATCH 3/3] KVM: perf: kvm events analysis tool Xiao Guangrong
2012-01-16 10:04 ` Avi Kivity
2012-01-17 2:30 ` Xiao Guangrong
2012-01-24 12:49 ` Avi Kivity
2012-01-16 10:08 ` Stefan Hajnoczi
2012-01-17 2:37 ` Xiao Guangrong
2012-01-17 11:59 ` Marcelo Tosatti
2012-01-24 12:51 ` Avi Kivity
2012-01-16 10:11 ` [RFC][PATCH] KVM: perf: a smart tool to analyse kvm events Avi Kivity
2012-01-17 2:30 ` Xiao Guangrong
2012-01-16 22:53 ` David Ahern
2012-01-17 2:41 ` Xiao Guangrong
2012-01-17 4:49 ` David Ahern
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