Message-ID: <52171E4F.2020109@nvidia.com>
Date: Fri, 23 Aug 2013 16:33:19 +0800
From: Jiejing Zhang <jiejzhang@nvidia.com>
Reply-To: <jiejzhang@nvidia.com>
Organization: Nvidia
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To: Peter Zijlstra <peterz@infradead.org>
CC: Steven Rostedt <rostedt@goodmis.org>, Jiejing Zhang <kzjeef@gmail.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Ingo Molnar <mingo@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Eric Miao <emiao@nvidia.com>
Subject: Re: [PATCH] ftrace: add tgid information in task switch event.
References: <1377097520-24898-1-git-send-email-jasozhang@nvidia.com> <20130821110944.32bdf03a@gandalf.local.home> <20130821152305.GD31370@twins.programming.kicks-ass.net>
In-Reply-To: <20130821152305.GD31370@twins.programming.kicks-ass.net>
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On 08/21/2013 11:23 PM, Peter Zijlstra wrote:
> On Wed, Aug 21, 2013 at 11:09:44AM -0400, Steven Rostedt wrote:
>>> From: Jiejing Zhang <jiejzhang@nvidia.com>
>>>
>>> ftrace only report pid in task switch event, which is
>>> actually thread ID in user space view, the comm of
>>> the thread will be like "Thread-1", "Compiler", etc
>>> in android system, it's useful if we can add tgid
>>> information in ftrace event to find out the process
>>> id, and the process id's comm will help us to figure
>>> out the application, which was useful on data analysis
>>> tools.
> Meh.. are you telling me you really can't do that otherwise?
>
> Adding this information makes the tracepoint slower for everybody else.
> How about you enable trace_sched_process_fork() and track things that
> way?
Thanks for the tip, I have tried fix this by avoid add tgid in ftrace,
actually the relationship between thread and process can be figure by 
analysis these two command's output:
`ps aTH -F` and `ps a -F`

also with fork event, it can totally avoid add such a patch in kernel.

Thanks.
>
> Also, last time I tried to change one of these stupid tracepoints
> userspace broke.. Rostedt says people should be using libtraceevent but
> I'm sceptical.
>
>>> Change-Id: Ia99f58a56d691d770b3beb2f76de0351e6194a4a
> That needs to die.

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