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authorLi Zefan <lizf@cn.fujitsu.com>2010-07-02 11:07:32 +0800
committerSteven Rostedt <rostedt@goodmis.org>2010-07-20 21:52:33 -0400
commite870e9a1240bcef1157ffaaf71dac63362e71904 (patch)
treeb8f57a68ff45b35dab8cdfa474e17622d275bdc6 /kernel/trace
parentcc5edb0eb9ce892b530e34a5d110382483587942 (diff)
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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')
-rw-r--r--kernel/trace/trace.c6
-rw-r--r--kernel/trace/trace.h3
-rw-r--r--kernel/trace/trace_events.c30
3 files changed, 36 insertions, 3 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
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 84d3f123e86f..7778f067fc8b 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -591,6 +591,7 @@ enum trace_iterator_flags {
TRACE_ITER_LATENCY_FMT = 0x20000,
TRACE_ITER_SLEEP_TIME = 0x40000,
TRACE_ITER_GRAPH_TIME = 0x80000,
+ TRACE_ITER_RECORD_CMD = 0x100000,
};
/*
@@ -723,6 +724,8 @@ filter_check_discard(struct ftrace_event_call *call, void *rec,
return 0;
}
+extern void trace_event_enable_cmd_record(bool enable);
+
extern struct mutex event_mutex;
extern struct list_head ftrace_events;
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index e8e6043f4d29..09b4fa6e4d3b 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -170,6 +170,26 @@ int ftrace_event_reg(struct ftrace_event_call *call, enum trace_reg type)
}
EXPORT_SYMBOL_GPL(ftrace_event_reg);
+void trace_event_enable_cmd_record(bool enable)
+{
+ struct ftrace_event_call *call;
+
+ mutex_lock(&event_mutex);
+ list_for_each_entry(call, &ftrace_events, list) {
+ if (!(call->flags & TRACE_EVENT_FL_ENABLED))
+ continue;
+
+ if (enable) {
+ tracing_start_cmdline_record();
+ call->flags |= TRACE_EVENT_FL_RECORDED_CMD;
+ } else {
+ tracing_stop_cmdline_record();
+ call->flags &= ~TRACE_EVENT_FL_RECORDED_CMD;
+ }
+ }
+ mutex_unlock(&event_mutex);
+}
+
static int ftrace_event_enable_disable(struct ftrace_event_call *call,
int enable)
{
@@ -179,13 +199,19 @@ static int ftrace_event_enable_disable(struct ftrace_event_call *call,
case 0:
if (call->flags & TRACE_EVENT_FL_ENABLED) {
call->flags &= ~TRACE_EVENT_FL_ENABLED;
- tracing_stop_cmdline_record();
+ if (call->flags & TRACE_EVENT_FL_RECORDED_CMD) {
+ tracing_stop_cmdline_record();
+ call->flags &= ~TRACE_EVENT_FL_RECORDED_CMD;
+ }
call->class->reg(call, TRACE_REG_UNREGISTER);
}
break;
case 1:
if (!(call->flags & TRACE_EVENT_FL_ENABLED)) {
- tracing_start_cmdline_record();
+ if (trace_flags & TRACE_ITER_RECORD_CMD) {
+ tracing_start_cmdline_record();
+ call->flags |= TRACE_EVENT_FL_RECORDED_CMD;
+ }
ret = call->class->reg(call, TRACE_REG_REGISTER);
if (ret) {
tracing_stop_cmdline_record();