linux-kernel - Re: Ftrace: can trace kthread?

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Message-ID: <1287654765.2237.18.camel@myhost>
Date:	Thu, 21 Oct 2010 17:52:45 +0800
From:	"Figo.zhang" <zhangtianfei@...dcoretech.com>
To:	Yong Zhang <yong.zhang0@...il.com>
Cc:	Li Zefan <lizf@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: Ftrace: can trace kthread?


> >
> > [root@...ost tracing]# ps -ax | grep flush
> > Warning: bad ps syntax, perhaps a bogus '-'? See http://procps.sf.net/faq.html
> >  1205 ?        S      0:01 [flush-8:0]
> > 11852 pts/1    S+     0:00 grep flush
> > [root@...ost tracing]#
> >
> > so my flusher pid is 1205, i do it as below:
> >
> > [root@...ost tracing]# echo 0 > tracing_enabled
> > [root@...ost tracing]# echo function > current_tracer
> > [root@...ost tracing]# echo 1205 > set_ftrace_pid
> > [root@...ost tracing]# echo 1 > tracing_enabled
> >
> > wait ... and open some pdf files, let system eat huge memory...
> >
> > [root@...ost tracing]# echo 0 > tracing_enabled
> > [root@...ost tracing]# cat trace
> > # tracer: function
> > #
> > #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
> > #              | |       |          |         |
> >
> >
> > but i canot trace nothing.
> 
> Is tracing_on enable(1) on your system?
> I enable it on my system by default, so I didn't show it in the previous mail.
> 

tracing_on is sure on, my kernel is 2.6.36-rc8, what is your kernel
version?

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