On Tue, Feb 22, 2011 at 10:08:18AM +0800, Li Zefan wrote: > 于 2011年02月22日 09:58, Han Pingtian 写道: > > On Mon, Feb 21, 2011 at 03:44:11PM +0800, Li Zefan wrote: > >> Han Pingtian wrote: > >>> It seems we need echo -1 to set_ftrace_pid to disable in. Or we'll get > >>> these error message when running ftrace_stress: > >>> > >> > >> kernel version? > > 2.6.32-114.0.1.el6.x86_64 , RHEL6.1. > >> > >> This is the result from latest kernel: > >> > >> # echo > set_ftrace_pid > >> # echo -1 > set_ftrace_pid > >> bash: echo: write error: Invalid argument > >> > > Looks like latest kernel changed the behaviour. But the > > The change came from commit 756d17ee7ee4fbc8238bdf97100af63e6ac441ef > > So we have to check the kernel version, or try both "echo > ..." and > "echo -1 > ...". I believe the second method is better. > > > Documentation/trace/ftrace.txt hasn't been updated: > > > > yum-updatesd-3111 [003] 1637.254683: lock_hrtimer_base > > <-hrtimer_try_to_cancel > > yum-updatesd-3111 [003] 1637.254685: fget_light <-do_sys_poll > > yum-updatesd-3111 [003] 1637.254686: pipe_poll <-do_sys_poll > > # echo -1 > set_ftrace_pid > > # cat trace |head > > # tracer: function > > # > > # TASK-PID CPU# TIMESTAMP FUNCTION
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