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| author | Oleg Nesterov <oleg@redhat.com> | 2013-08-06 18:08:47 +0200 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2013-08-13 21:06:30 -0400 |
| commit | d027e6a9c83440bf1ca9e5503539d58d8e0914f1 (patch) | |
| tree | 8f7397e15dd463c878939fa9d063adf167580573 /include/trace | |
| parent | 12473965c38a527a0c6f7a38d23edce60957f873 (diff) | |
| download | linux-d027e6a9c83440bf1ca9e5503539d58d8e0914f1.tar.gz linux-d027e6a9c83440bf1ca9e5503539d58d8e0914f1.tar.bz2 linux-d027e6a9c83440bf1ca9e5503539d58d8e0914f1.zip | |
tracing/perf: Avoid perf_trace_buf_*() in perf_trace_##call() when possible
perf_trace_buf_prepare() + perf_trace_buf_submit(task => NULL)
make no sense if hlist_empty(head). Change perf_trace_##call()
to check ->perf_events beforehand and do nothing if it is empty.
This removes the overhead for tasks without events associated
with them. For example, "perf record -e sched:sched_switch -p1"
attaches the counter(s) to the single task, but every task in
system will do perf_trace_buf_prepare/submit() just to realize
that it was not attached to this event.
However, we can only do this if __task == NULL, so we also add
the __builtin_constant_p(__task) check.
With this patch "perf bench sched pipe" shows approximately 4%
improvement when "perf record -p1" runs in parallel, many thanks
to Steven for the testing.
Link: http://lkml.kernel.org/r/20130806160847.GA2746@redhat.com
Tested-by: David Ahern <dsahern@gmail.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'include/trace')
| -rw-r--r-- | include/trace/ftrace.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h index 4163d93ccf38..5c7ab17cbb02 100644 --- a/include/trace/ftrace.h +++ b/include/trace/ftrace.h @@ -667,6 +667,12 @@ perf_trace_##call(void *__data, proto) \ int rctx; \ \ __data_size = ftrace_get_offsets_##call(&__data_offsets, args); \ + \ + head = this_cpu_ptr(event_call->perf_events); \ + if (__builtin_constant_p(!__task) && !__task && \ + hlist_empty(head)) \ + return; \ + \ __entry_size = ALIGN(__data_size + sizeof(*entry) + sizeof(u32),\ sizeof(u64)); \ __entry_size -= sizeof(u32); \ @@ -681,7 +687,6 @@ perf_trace_##call(void *__data, proto) \ \ { assign; } \ \ - head = this_cpu_ptr(event_call->perf_events); \ perf_trace_buf_submit(entry, __entry_size, rctx, __addr, \ __count, &__regs, head, __task); \ } |