linux-kernel - Re: [PATCH] ftrace: add tgid information in task switch event.

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Message-ID: <52171E4F.2020109@nvidia.com>
Date:	Fri, 23 Aug 2013 16:33:19 +0800
From:	Jiejing Zhang <jiejzhang@...dia.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	Jiejing Zhang <kzjeef@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Eric Miao <emiao@...dia.com>
Subject: Re: [PATCH] ftrace: add tgid information in task switch event.


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@...dia.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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