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    SubjectRe: Ftrace: can trace kthread?
    From
    On Thu, Oct 21, 2010 at 4:59 PM, Figo.zhang
    <zhangtianfei@leadcoretech.com> wrote:
    >
    >> I just
    >> echo  0 > tracing_enabled
    >> echo function > current_tracer
    >> echo 374(pid of flush) > set_ftrace_pid
    >> echo 1 > tracing_enabled
    >> wait some time
    >> echo 0 > tracing_enabled
    >> cat trace
    >>
    >> So I think this answer your question "could kthread be traced?"
    >
    > i do it the same of you.
    >
    > [root@myhost 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@myhost tracing]#
    >
    > so my flusher pid is 1205, i do it as below:
    >
    > [root@myhost tracing]# echo 0 > tracing_enabled
    > [root@myhost tracing]# echo function > current_tracer
    > [root@myhost tracing]# echo 1205 > set_ftrace_pid
    > [root@myhost tracing]# echo 1 > tracing_enabled
    >
    > wait ... and open some pdf files, let system eat huge memory...
    >
    > [root@myhost tracing]# echo 0 > tracing_enabled
    > [root@myhost 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.

    Thanks,
    Yong
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