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Subject[PATCH -tip -v12 11/11] tracing: Add kprobes event profiling interface
Date
Add profiling interaces for each kprobes event.

Changes from v11:
- Fix a typo and remove redundant check.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
---
Documentation/trace/kprobetrace.txt | 8 ++++++
kernel/trace/trace_kprobe.c | 45 +++++++++++++++++++++++++++++++++++
2 files changed, 53 insertions(+), 0 deletions(-)
diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
index 437ad49..9c6be05 100644
--- a/Documentation/trace/kprobetrace.txt
+++ b/Documentation/trace/kprobetrace.txt
@@ -69,6 +69,14 @@ filter:
names and field names for describing filters.


+Event Profiling
+---------------
+ You can check the total number of probe hits and probe miss-hits via
+/sys/kernel/debug/tracing/kprobe_profile.
+ The first column is event name, the second is the number of probe hits,
+the third is the number of probe miss-hits.
+
+
Usage examples
--------------
To add a probe as a new event, write a new definition to kprobe_events
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 3444d1d..21e619f 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -178,6 +178,7 @@ struct trace_probe {
struct kprobe kp;
struct kretprobe rp;
};
+ unsigned long nhits;
const char *symbol; /* symbol name */
struct ftrace_event_call call;
unsigned int nr_args;
@@ -766,6 +767,39 @@ static const struct file_operations kprobe_events_ops = {
.write = probes_write,
};

+/* Probes profiling interfaces */
+static int profile_seq_show(struct seq_file *m, void *v)
+{
+ struct trace_probe *tp = v;
+
+ seq_printf(m, "%s", tp->call.name);
+
+ seq_printf(m, "\t%8lu %8lu\n", tp->nhits,
+ probe_is_return(tp) ? tp->rp.kp.nmissed : tp->kp.nmissed);
+
+ return 0;
+}
+
+static const struct seq_operations profile_seq_op = {
+ .start = probes_seq_start,
+ .next = probes_seq_next,
+ .stop = probes_seq_stop,
+ .show = profile_seq_show
+};
+
+static int profile_open(struct inode *inode, struct file *file)
+{
+ return seq_open(file, &profile_seq_op);
+}
+
+static const struct file_operations kprobe_profile_ops = {
+ .owner = THIS_MODULE,
+ .open = profile_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
/* Kprobe handler */
static __kprobes int kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
{
@@ -776,6 +810,8 @@ static __kprobes int kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
unsigned long irq_flags;
struct ftrace_event_call *call = &tp->call;

+ tp->nhits++;
+
local_save_flags(irq_flags);
pc = preempt_count();

@@ -1152,9 +1188,18 @@ static __init int init_kprobe_trace(void)
entry = debugfs_create_file("kprobe_events", 0644, d_tracer,
NULL, &kprobe_events_ops);

+ /* Event list interface */
if (!entry)
pr_warning("Could not create debugfs "
"'kprobe_events' entry\n");
+
+ /* Profile interface */
+ entry = debugfs_create_file("kprobe_profile", 0444, d_tracer,
+ NULL, &kprobe_profile_ops);
+
+ if (!entry)
+ pr_warning("Could not create debugfs "
+ "'kprobe_profile' entry\n");
return 0;
}
fs_initcall(init_kprobe_trace);

--
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com


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