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Subject[PATCH 3/5] tracing: optimization of branch tracer
From: Witold Baryluk <baryluk@smp.if.uj.edu.pl>

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>
---
include/linux/compiler.h | 6 ++----
1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index d95da10..6faa7e5 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -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 */
--
1.6.2
--


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