diff options
| 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 /kernel/trace/trace.c | |
| parent | cc5edb0eb9ce892b530e34a5d110382483587942 (diff) | |
| download | blackbird-op-linux-e870e9a1240bcef1157ffaaf71dac63362e71904.tar.gz blackbird-op-linux-e870e9a1240bcef1157ffaaf71dac63362e71904.zip | |
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 'kernel/trace/trace.c')
| -rw-r--r-- | kernel/trace/trace.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 8683dec6946b..af9042977c08 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -344,7 +344,7 @@ static DECLARE_WAIT_QUEUE_HEAD(trace_wait); /* trace_flags holds trace_options default values */ unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK | TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_SLEEP_TIME | - TRACE_ITER_GRAPH_TIME; + TRACE_ITER_GRAPH_TIME | TRACE_ITER_RECORD_CMD; static int trace_stop_count; static DEFINE_SPINLOCK(tracing_start_lock); @@ -428,6 +428,7 @@ static const char *trace_options[] = { "latency-format", "sleep-time", "graph-time", + "record-cmd", NULL }; @@ -2561,6 +2562,9 @@ static void set_tracer_flags(unsigned int mask, int enabled) trace_flags |= mask; else trace_flags &= ~mask; + + if (mask == TRACE_ITER_RECORD_CMD) + trace_event_enable_cmd_record(enabled); } static ssize_t |
