Commit 97e7e4f3 authored Mar 17, 2009 by Witold Baryluk Committed by Steven Rostedt Mar 17, 2009

tracing: optimization of branch tracer



Impact: better performance for if branch tracer

Use an array to count the hit and misses of a conditional instead
of using another conditional. This cuts down on saturation of branch
predictions and increases performance of modern pipelined architectures.

Signed-off-by: Witold Baryluk <baryluk@smp.if.uj.edu.pl>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>

parent af4617bd

include/linux/compiler.h

+2 −4

Original line number	Diff line number	Diff line
		@@ -68,6 +68,7 @@ struct ftrace_branch_data {
		unsigned long miss;
		unsigned long hit;
		};
		unsigned long miss_hit[2];
		};
		};

		@@ -125,10 +126,7 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
		.line = __LINE__, \
		}; \
		______r = !!(cond); \
		if (______r) \
		______f.hit++; \
		else \
		______f.miss++; \
		______f.miss_hit[______r]++; \
		______r; \
		}))
		#endif /* CONFIG_PROFILE_ALL_BRANCHES */