Steven Rostedt 4cd8587ce8 btrfs: Use trace condition for get_extent tracepoint ... Doing an if statement to test some condition to know if we should trigger a tracepoint is pointless when tracing is disabled. This just adds overhead and wastes a branch prediction. This is why the TRACE_EVENT_CONDITION() was created. It places the check inside the jump label so that the branch does not happen unless tracing is enabled. That is, instead of doing: if (em) trace_btrfs_get_extent(root, em); Which is basically this: if (em) if (static_key(trace_btrfs_get_extent)) { Using a TRACE_EVENT_CONDITION() we can just do: trace_btrfs_get_extent(root, em); And the condition trace event will do: if (static_key(trace_btrfs_get_extent)) { if (em) { ... The static key is a non conditional jump (or nop) that is faster than having to check if em is NULL or not. Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Josef Bacik <jbacik@fusionio.com> Signed-off-by: Chris Mason <chris.mason@fusionio.com>		2013-11-20 20:44:47 -05:00
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events	btrfs: Use trace condition for get_extent tracepoint	2013-11-20 20:44:47 -05:00
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