commit 8e5799b1ad2a0567fdfaaf0e91b40efee010f2c1
author Peter Zijlstra <a.p.zijlstra@chello.nl> Tue Jun 02 15:08:15 2009 +0200
committer Ingo Molnar <mingo@elte.hu> Tue Jun 02 21:45:29 2009 +0200
tree bd3f45c348f48411a4496229572643211cbd59b8
parent 53e111a730ea8b002d57dd226098c12789993329

perf_counter: Add unique counter id

Stephan raised the issue that we currently cannot distinguish between
similar counters within a group (PERF_RECORD_GROUP uses the config
value as identifier).

Therefore, generate a new ID for each counter using a global u64
sequence counter.

Reported-by: Stephane Eranian <eranian@googlemail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/perf_counter.c

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index caa012c..978ecfc 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1510,6 +1510,8 @@
 	if (counter->hw_event.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
 		values[n++] = counter->total_time_running +
 			atomic64_read(&counter->child_total_time_running);
+	if (counter->hw_event.read_format & PERF_FORMAT_ID)
+		values[n++] = counter->id;
 	mutex_unlock(&counter->child_mutex);
 
 	if (count < n * sizeof(u64))
@@ -2303,7 +2305,7 @@
 		u32 pid, tid;
 	} tid_entry;
 	struct {
-		u64 event;
+		u64 id;
 		u64 counter;
 	} group_entry;
 	struct perf_callchain_entry *callchain = NULL;
@@ -2416,7 +2418,7 @@
 			if (sub != counter)
 				sub->pmu->read(sub);
 
-			group_entry.event = sub->hw_event.config;
+			group_entry.id = sub->id;
 			group_entry.counter = atomic64_read(&sub->count);
 
 			perf_output_put(&handle, group_entry);
@@ -3375,6 +3377,8 @@
 	return counter;
 }
 
+static atomic64_t perf_counter_id;
+
 /**
  * sys_perf_counter_open - open a performance counter, associate it to a task/cpu
  *
@@ -3470,6 +3474,7 @@
 	mutex_unlock(&current->perf_counter_mutex);
 
 	counter->ns = get_pid_ns(current->nsproxy->pid_ns);
+	counter->id = atomic64_inc_return(&perf_counter_id);
 
 	fput_light(counter_file, fput_needed2);