Oleg Nesterov d027e6a9c8 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>		2013-08-13 21:06:30 -04:00
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events	tracing/perf: Reimplement TP_perf_assign() logic	2013-08-13 21:05:57 -04:00
define_trace.h	tracing: Add DEFINE_EVENT_FN() macro	2013-06-20 22:24:32 -07:00
ftrace.h	tracing/perf: Avoid perf_trace_buf_*() in perf_trace_##call() when possible	2013-08-13 21:06:30 -04:00
syscall.h	tracing: Add missing syscall_metadata comment	2013-07-01 20:34:25 -04:00