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>
hifive-unleashed-5.1
Steven Rostedt
Ingo Molnar
parent
bac28bfe42
commit
2bcd521a68
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@ -53,6 +53,14 @@
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#define LIKELY_PROFILE()
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#endif
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#ifdef CONFIG_PROFILE_ALL_BRANCHES
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#define BRANCH_PROFILE() VMLINUX_SYMBOL(__start_branch_profile) = .; \
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*(_ftrace_branch) \
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VMLINUX_SYMBOL(__stop_branch_profile) = .;
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#else
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#define BRANCH_PROFILE()
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#endif
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/* .data section */
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#define DATA_DATA \
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*(.data) \
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@ -72,7 +80,8 @@
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VMLINUX_SYMBOL(__start___tracepoints) = .; \
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*(__tracepoints) \
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VMLINUX_SYMBOL(__stop___tracepoints) = .; \
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LIKELY_PROFILE()
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LIKELY_PROFILE() \
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BRANCH_PROFILE()
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#define RO_DATA(align) \
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. = ALIGN((align)); \
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@ -63,8 +63,16 @@ struct ftrace_branch_data {
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const char *func;
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const char *file;
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unsigned line;
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unsigned long correct;
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unsigned long incorrect;
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union {
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struct {
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unsigned long correct;
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unsigned long incorrect;
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};
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struct {
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unsigned long miss;
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unsigned long hit;
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};
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};
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};
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/*
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@ -103,6 +111,32 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
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# ifndef unlikely
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# define unlikely(x) (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 0))
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# endif
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#ifdef CONFIG_PROFILE_ALL_BRANCHES
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/*
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* "Define 'is'", Bill Clinton
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* "Define 'if'", Steven Rostedt
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*/
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#define if(cond) if (__builtin_constant_p((cond)) ? !!(cond) : \
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({ \
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int ______r; \
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static struct ftrace_branch_data \
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__attribute__((__aligned__(4))) \
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__attribute__((section("_ftrace_branch"))) \
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______f = { \
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.func = __func__, \
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.file = __FILE__, \
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.line = __LINE__, \
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}; \
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______r = !!(cond); \
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if (______r) \
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______f.hit++; \
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else \
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______f.miss++; \
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______r; \
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}))
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#endif /* CONFIG_PROFILE_ALL_BRANCHES */
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#else
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# define likely(x) __builtin_expect(!!(x), 1)
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# define unlikely(x) __builtin_expect(!!(x), 0)
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@ -173,6 +173,22 @@ config TRACE_BRANCH_PROFILING
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Say N if unsure.
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config PROFILE_ALL_BRANCHES
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bool "Profile all if conditionals"
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depends on TRACE_BRANCH_PROFILING
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help
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This tracer profiles all branch conditions. Every if ()
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taken in the kernel is recorded whether it hit or miss.
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The results will be displayed in:
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/debugfs/tracing/profile_branch
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This configuration, when enabled, will impose a great overhead
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on the system. This should only be enabled when the system
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is to be analyzed
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Say N if unsure.
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config TRACING_BRANCHES
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bool
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help
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@ -185,6 +185,7 @@ EXPORT_SYMBOL(ftrace_likely_update);
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struct ftrace_pointer {
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void *start;
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void *stop;
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int hit;
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};
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static void *
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@ -223,13 +224,17 @@ static void t_stop(struct seq_file *m, void *p)
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static int t_show(struct seq_file *m, void *v)
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{
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struct ftrace_pointer *fp = m->private;
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struct ftrace_branch_data *p = v;
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const char *f;
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long percent;
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if (v == (void *)1) {
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seq_printf(m, " correct incorrect %% "
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" Function "
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if (fp->hit)
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seq_printf(m, " miss hit %% ");
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else
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seq_printf(m, " correct incorrect %% ");
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seq_printf(m, " Function "
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" File Line\n"
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" ------- --------- - "
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" -------- "
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@ -243,6 +248,9 @@ static int t_show(struct seq_file *m, void *v)
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f--;
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f++;
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/*
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* The miss is overlayed on correct, and hit on incorrect.
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*/
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if (p->correct) {
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percent = p->incorrect * 100;
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percent /= p->correct + p->incorrect;
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@ -284,6 +292,18 @@ static const struct file_operations tracing_branch_fops = {
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.llseek = seq_lseek,
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};
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#ifdef CONFIG_PROFILE_ALL_BRANCHES
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extern unsigned long __start_branch_profile[];
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extern unsigned long __stop_branch_profile[];
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static struct ftrace_pointer ftrace_branch_pos = {
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.start = __start_branch_profile,
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.stop = __stop_branch_profile,
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.hit = 1,
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};
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#endif /* CONFIG_PROFILE_ALL_BRANCHES */
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extern unsigned long __start_annotated_branch_profile[];
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extern unsigned long __stop_annotated_branch_profile[];
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@ -306,6 +326,15 @@ static __init int ftrace_branch_init(void)
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pr_warning("Could not create debugfs "
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"'profile_annotatet_branch' entry\n");
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#ifdef CONFIG_PROFILE_ALL_BRANCHES
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entry = debugfs_create_file("profile_branch", 0444, d_tracer,
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&ftrace_branch_pos,
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&tracing_branch_fops);
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if (!entry)
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pr_warning("Could not create debugfs"
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" 'profile_branch' entry\n");
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#endif
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return 0;
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}
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