From 97e7e4f391cac2b00417b581b432533d245d4fd0 Mon Sep 17 00:00:00 2001 From: Witold Baryluk Date: Tue, 17 Mar 2009 21:15:44 +0100 Subject: 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 Signed-off-by: Steven Rostedt --- include/linux/compiler.h | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'include/linux/compiler.h') diff --git a/include/linux/compiler.h b/include/linux/compiler.h index d95da1020f1c..6faa7e549de4 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 */ -- cgit v1.2.3 From aeeae86859f4319de0a4946b44771d9926eeed54 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 7 Apr 2009 07:59:41 -0700 Subject: Fix build errors due to CONFIG_BRANCH_TRACER=y The code that enables branch tracing for all (non-constant) branches plays games with the preprocessor and #define's the C 'if ()' construct to do tracing. That's all fine, but it fails for some unusual but valid C code that is sometimes used in macros, notably by the intel-iommu code: if (i=drhd->iommu, drhd->ignored) .. because now the preprocessor complains about multiple arguments to the 'if' macro. So make the macro expansion of this particularly horrid trick use varargs, and handle the case of comma-expressions in if-statements. Use another macro to do it cleanly in just one place. This replaces a patch by David (and acked by Steven) that did this all inside that one already-too-horrid macro. Tested-by: Ingo Molnar Cc: David Woodhouse Cc: Steven Rostedt Signed-off-by: Linus Torvalds --- include/linux/compiler.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'include/linux/compiler.h') diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 6faa7e549de4..cebfdcd3dbdd 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -114,7 +114,9 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); * "Define 'is'", Bill Clinton * "Define 'if'", Steven Rostedt */ -#define if(cond) if (__builtin_constant_p((cond)) ? !!(cond) : \ +#define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) ) +#define __trace_if(cond) \ + if (__builtin_constant_p((cond)) ? !!(cond) : \ ({ \ int ______r; \ static struct ftrace_branch_data \ -- cgit v1.2.3