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| author | Li Zefan <lizf@cn.fujitsu.com> | 2010-07-02 11:07:32 +0800 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2010-07-20 21:52:33 -0400 |
| commit | e870e9a1240bcef1157ffaaf71dac63362e71904 (patch) | |
| tree | b8f57a68ff45b35dab8cdfa474e17622d275bdc6 /include/linux/ftrace_event.h | |
| parent | cc5edb0eb9ce892b530e34a5d110382483587942 (diff) | |
| download | kernel_goldelico_gta04-e870e9a1240bcef1157ffaaf71dac63362e71904.zip kernel_goldelico_gta04-e870e9a1240bcef1157ffaaf71dac63362e71904.tar.gz kernel_goldelico_gta04-e870e9a1240bcef1157ffaaf71dac63362e71904.tar.bz2 | |
tracing: Allow to disable cmdline recording
We found that even enabling a single trace event that will rarely be
triggered can add big overhead to context switch.
(lmbench context switch test)
-------------------------------------------------
2p/0K 2p/16K 2p/64K 8p/16K 8p/64K 16p/16K 16p/64K
ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw
------ ------ ------ ------ ------ ------- -------
2.19 2.3 2.21 2.56 2.13 2.54 2.07
2.39 2.51 2.35 2.75 2.27 2.81 2.24
The overhead is 6% ~ 11%.
It's because when a trace event is enabled 3 tracepoints (sched_switch,
sched_wakeup, sched_wakeup_new) will be activated to map pid to cmdname.
We'd like to avoid this overhead, so add a trace option '(no)record-cmd'
to allow to disable cmdline recording.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4C2D57F4.2050204@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'include/linux/ftrace_event.h')
| -rw-r--r-- | include/linux/ftrace_event.h | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h index 01df7ca..2b7b139 100644 --- a/include/linux/ftrace_event.h +++ b/include/linux/ftrace_event.h @@ -152,11 +152,13 @@ extern int ftrace_event_reg(struct ftrace_event_call *event, enum { TRACE_EVENT_FL_ENABLED_BIT, TRACE_EVENT_FL_FILTERED_BIT, + TRACE_EVENT_FL_RECORDED_CMD_BIT, }; enum { - TRACE_EVENT_FL_ENABLED = (1 << TRACE_EVENT_FL_ENABLED_BIT), - TRACE_EVENT_FL_FILTERED = (1 << TRACE_EVENT_FL_FILTERED_BIT), + TRACE_EVENT_FL_ENABLED = (1 << TRACE_EVENT_FL_ENABLED_BIT), + TRACE_EVENT_FL_FILTERED = (1 << TRACE_EVENT_FL_FILTERED_BIT), + TRACE_EVENT_FL_RECORDED_CMD = (1 << TRACE_EVENT_FL_RECORDED_CMD_BIT), }; struct ftrace_event_call { @@ -174,6 +176,7 @@ struct ftrace_event_call { * 32 bit flags: * bit 1: enabled * bit 2: filter_active + * bit 3: enabled cmd record * * Changes to flags must hold the event_mutex. * |