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 d95da1020f1..6faa7e549de 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 v1.2.3-70-g09d2 From d9ad8bc0ca823705413f75b50c442a88cc518b35 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Sun, 5 Apr 2009 16:20:02 +0200 Subject: branch tracer: Fix for enabling branch profiling makes sparse unusable One of the changes between kernels 2.6.28 and 2.6.29 is that a branch profiler has been added for if() statements. Unfortunately this patch makes the sparse output unusable with CONFIG_TRACE_BRANCH_PROFILING=y: when branch profiling is enabled, sparse prints so much false positives that the real issues are no longer visible. This behavior can be reproduced as follows: * enable CONFIG_TRACE_BRANCH_PROFILING, e.g. by running make allyesconfig or make allmodconfig. * run make C=2 Result: a huge number of the following sparse warnings. ... include/linux/cpumask.h:547:2: warning: symbol '______r' shadows an earlier one include/linux/cpumask.h:547:2: originally declared here ... The patch below fixes this by disabling branch profiling while analyzing the kernel code with sparse. See also: * http://lkml.org/lkml/2008/11/21/18 * http://bugzilla.kernel.org/show_bug.cgi?id=12925 Signed-off-by: Bart Van Assche Cc: Andrew Morton Cc: Steven Rostedt LKML-Reference: <200904051620.02311.bart.vanassche@gmail.com> Signed-off-by: Ingo Molnar --- include/linux/compiler.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include/linux/compiler.h') diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 6faa7e549de..8872ad6dd89 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -76,7 +76,8 @@ struct ftrace_branch_data { * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code * to disable branch tracing on a per file basis. */ -#if defined(CONFIG_TRACE_BRANCH_PROFILING) && !defined(DISABLE_BRANCH_PROFILING) +#if defined(CONFIG_TRACE_BRANCH_PROFILING) \ + && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__) void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); #define likely_notrace(x) __builtin_expect(!!(x), 1) -- cgit v1.2.3-70-g09d2 From ab3c9c686e22ab264269337ce7b75d9760211198 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 7 Apr 2009 07:59:41 -0700 Subject: branch tracer, intel-iommu: fix build with CONFIG_BRANCH_TRACER=y Fix the branch tracer barfing on comma statements within if () statements. Signed-off-by: Ingo Molnar --- 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 8872ad6dd89..37bcb50a4d7 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -115,7 +115,9 @@ 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 v1.2.3-70-g09d2