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authorSteven Rostedt <srostedt@redhat.com>2008-11-21 01:30:54 -0500
committerIngo Molnar <mingo@elte.hu>2008-11-23 05:41:01 -0500
commit2bcd521a684cc94befbe2ce7d5b613c841b0d304 (patch)
tree63bc4dbc52defa27c8cac9e46dddadfcb36c1c7a /include
parentbac28bfe42ba98ee67503f78984d1d5e1ebbbb78 (diff)
trace: profile all if conditionals
Impact: feature to profile if statements This patch adds a branch profiler for all if () statements. The results will be found in: /debugfs/tracing/profile_branch For example: miss hit % Function File Line ------- --------- - -------- ---- ---- 0 1 100 x86_64_start_reservations head64.c 127 0 1 100 copy_bootdata head64.c 69 1 0 0 x86_64_start_kernel head64.c 111 32 0 0 set_intr_gate desc.h 319 1 0 0 reserve_ebda_region head.c 51 1 0 0 reserve_ebda_region head.c 47 0 1 100 reserve_ebda_region head.c 42 0 0 X maxcpus main.c 165 Miss means the branch was not taken. Hit means the branch was taken. The percent is the percentage the branch was taken. This adds a significant amount of overhead and should only be used by those analyzing their system. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include')
-rw-r--r--include/asm-generic/vmlinux.lds.h11
-rw-r--r--include/linux/compiler.h38
2 files changed, 46 insertions, 3 deletions
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 8bccb49981e5..eba835a2c2cd 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -53,6 +53,14 @@
53#define LIKELY_PROFILE() 53#define LIKELY_PROFILE()
54#endif 54#endif
55 55
56#ifdef CONFIG_PROFILE_ALL_BRANCHES
57#define BRANCH_PROFILE() VMLINUX_SYMBOL(__start_branch_profile) = .; \
58 *(_ftrace_branch) \
59 VMLINUX_SYMBOL(__stop_branch_profile) = .;
60#else
61#define BRANCH_PROFILE()
62#endif
63
56/* .data section */ 64/* .data section */
57#define DATA_DATA \ 65#define DATA_DATA \
58 *(.data) \ 66 *(.data) \
@@ -72,7 +80,8 @@
72 VMLINUX_SYMBOL(__start___tracepoints) = .; \ 80 VMLINUX_SYMBOL(__start___tracepoints) = .; \
73 *(__tracepoints) \ 81 *(__tracepoints) \
74 VMLINUX_SYMBOL(__stop___tracepoints) = .; \ 82 VMLINUX_SYMBOL(__stop___tracepoints) = .; \
75 LIKELY_PROFILE() 83 LIKELY_PROFILE() \
84 BRANCH_PROFILE()
76 85
77#define RO_DATA(align) \ 86#define RO_DATA(align) \
78 . = ALIGN((align)); \ 87 . = ALIGN((align)); \
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 0628a2013fae..ea7c6be354b7 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -63,8 +63,16 @@ struct ftrace_branch_data {
63 const char *func; 63 const char *func;
64 const char *file; 64 const char *file;
65 unsigned line; 65 unsigned line;
66 unsigned long correct; 66 union {
67 unsigned long incorrect; 67 struct {
68 unsigned long correct;
69 unsigned long incorrect;
70 };
71 struct {
72 unsigned long miss;
73 unsigned long hit;
74 };
75 };
68}; 76};
69 77
70/* 78/*
@@ -103,6 +111,32 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
103# ifndef unlikely 111# ifndef unlikely
104# define unlikely(x) (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 0)) 112# define unlikely(x) (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 0))
105# endif 113# endif
114
115#ifdef CONFIG_PROFILE_ALL_BRANCHES
116/*
117 * "Define 'is'", Bill Clinton
118 * "Define 'if'", Steven Rostedt
119 */
120#define if(cond) if (__builtin_constant_p((cond)) ? !!(cond) : \
121 ({ \
122 int ______r; \
123 static struct ftrace_branch_data \
124 __attribute__((__aligned__(4))) \
125 __attribute__((section("_ftrace_branch"))) \
126 ______f = { \
127 .func = __func__, \
128 .file = __FILE__, \
129 .line = __LINE__, \
130 }; \
131 ______r = !!(cond); \
132 if (______r) \
133 ______f.hit++; \
134 else \
135 ______f.miss++; \
136 ______r; \
137 }))
138#endif /* CONFIG_PROFILE_ALL_BRANCHES */
139
106#else 140#else
107# define likely(x) __builtin_expect(!!(x), 1) 141# define likely(x) __builtin_expect(!!(x), 1)
108# define unlikely(x) __builtin_expect(!!(x), 0) 142# define unlikely(x) __builtin_expect(!!(x), 0)