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tracing: likely/unlikely branch annotation tracer

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Impact: new likely/unlikely branch tracer

This patch adds a way to record the instances of the likely() and unlikely()
branch condition annotations.

When "unlikely" is set in /debugfs/tracing/iter_ctrl the unlikely conditions
will be added to any of the ftrace tracers. The change takes effect when
a new tracer is passed into the current_tracer file.

For example:

 bash-3471  [003]   357.014755: [INCORRECT] sched_info_dequeued:sched_stats.h:177
 bash-3471  [003]   357.014756: [correct] update_curr:sched_fair.c:489
 bash-3471  [003]   357.014758: [correct] calc_delta_fair:sched_fair.c:411
 bash-3471  [003]   357.014759: [correct] account_group_exec_runtime:sched_stats.h:356
 bash-3471  [003]   357.014761: [correct] update_curr:sched_fair.c:489
 bash-3471  [003]   357.014763: [INCORRECT] calc_delta_fair:sched_fair.c:411
 bash-3471  [003]   357.014765: [correct] calc_delta_mine:sched.c:1279

Which shows the normal tracer heading, as well as whether the condition was
correct "[correct]" or was mistaken "[INCORRECT]", followed by the function,
file name and line number.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Steven Rostedt
2008-11-12 00:14:40 -05:00
committed by Ingo Molnar
parent 1f0d69a9fc
commit 52f232cb72
5 changed files with 210 additions and 0 deletions
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39
kernel/trace/trace.h
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@@ -22,6 +22,7 @@ enum trace_type {
TRACE_SPECIAL,
TRACE_MMIO_RW,
TRACE_MMIO_MAP,
TRACE_UNLIKELY,
TRACE_BOOT_CALL,
TRACE_BOOT_RET,
TRACE_FN_RET,
@@ -134,6 +135,16 @@ struct trace_boot_ret {
struct boot_trace_ret boot_ret;
};
#define TRACE_FUNC_SIZE 30
#define TRACE_FILE_SIZE 20
struct trace_unlikely {
struct trace_entry ent;
unsigned line;
char func[TRACE_FUNC_SIZE+1];
char file[TRACE_FILE_SIZE+1];
char correct;
};
/*
* trace_flag_type is an enumeration that holds different
* states when a trace occurs. These are:
@@ -236,6 +247,7 @@ extern void __ftrace_bad_type(void);
TRACE_MMIO_MAP); \
IF_ASSIGN(var, ent, struct trace_boot_call, TRACE_BOOT_CALL);\
IF_ASSIGN(var, ent, struct trace_boot_ret, TRACE_BOOT_RET);\
IF_ASSIGN(var, ent, struct trace_unlikely, TRACE_UNLIKELY); \
IF_ASSIGN(var, ent, struct ftrace_ret_entry, TRACE_FN_RET);\
__ftrace_bad_type(); \
} while (0)
@@ -456,6 +468,9 @@ enum trace_iterator_flags {
TRACE_ITER_SCHED_TREE = 0x200,
TRACE_ITER_PRINTK = 0x400,
TRACE_ITER_PREEMPTONLY = 0x800,
#ifdef CONFIG_UNLIKELY_TRACER
TRACE_ITER_UNLIKELY = 0x1000,
#endif
};
/*
@@ -515,4 +530,28 @@ static inline void ftrace_preempt_enable(int resched)
preempt_enable_notrace();
}
#ifdef CONFIG_UNLIKELY_TRACER
extern int enable_unlikely_tracing(struct trace_array *tr);
extern void disable_unlikely_tracing(void);
static inline int trace_unlikely_enable(struct trace_array *tr)
{
if (trace_flags & TRACE_ITER_UNLIKELY)
return enable_unlikely_tracing(tr);
return 0;
}
static inline void trace_unlikely_disable(void)
{
/* due to races, always disable */
disable_unlikely_tracing();
}
#else
static inline int trace_unlikely_enable(struct trace_array *tr)
{
return 0;
}
static inline void trace_unlikely_disable(void)
{
}
#endif /* CONFIG_UNLIKELY_TRACER */
#endif /* _LINUX_KERNEL_TRACE_H */