tracing: Add kprobes event profiling interface

Add profiling interfaces for each kprobes event. This interface provides
how many times each probe hit or missed.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Frank Ch. Eigler <fche@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Przemysław Pawełczyk <przemyslaw@pawelczyk.it>
Cc: Roland McGrath <roland@redhat.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
LKML-Reference: <20090813203541.31965.8452.stgit@localhost.localdomain>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

2 files changed, 51 insertions, 0 deletions

diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
index 5e59e854e71b..3de751747164 100644
--- a/Documentation/trace/kprobetrace.txt
+++ b/Documentation/trace/kprobetrace.txt
@@ -70,6 +70,14 @@ 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 9c067bf47d50..ce68197767de 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -184,6 +184,7 @@ struct trace_probe {
                 struct kprobe           kp;
                 struct kretprobe        rp;
         };
+        unsigned long           nhit;
         const char              *symbol;        /* symbol name */
         struct ftrace_event_call        call;
         struct trace_event              event;
@@ -781,6 +782,37 @@ static const struct file_operations kprobe_events_ops = {
         .write          = probes_write,
 };
 
+/* Probes profiling interfaces */
+static int probes_profile_seq_show(struct seq_file *m, void *v)
+{
+        struct trace_probe *tp = v;
+
+        seq_printf(m, "  %-44s %15lu %15lu\n", tp->call.name, tp->nhit,
+                   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   = probes_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)
 {
@@ -791,6 +823,8 @@ 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->nhit++;
+
         local_save_flags(irq_flags);
         pc = preempt_count();
 
@@ -1140,9 +1174,18 @@ 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);