perf_counter: add ioctl(PERF_COUNTER_IOC_RESET)
Provide a way to reset an existing counter - this eases PAPI
libraries around perfcounters.
Similar to read() it doesn't collapse pending child counters.
[ Impact: new perfcounter fd ioctl method to reset counters ]
Suggested-by: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20090505155437.022272933@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 17b6310..0fcbf34 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -160,6 +160,7 @@
#define PERF_COUNTER_IOC_ENABLE _IO ('$', 0)
#define PERF_COUNTER_IOC_DISABLE _IO ('$', 1)
#define PERF_COUNTER_IOC_REFRESH _IOW('$', 2, u32)
+#define PERF_COUNTER_IOC_RESET _IO ('$', 3)
/*
* Structure of the page that can be mapped via mmap
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index ba5e921..6e6834e 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1288,6 +1288,11 @@
return events;
}
+static void perf_counter_reset(struct perf_counter *counter)
+{
+ atomic_set(&counter->count, 0);
+}
+
static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct perf_counter *counter = file->private_data;
@@ -1303,6 +1308,9 @@
case PERF_COUNTER_IOC_REFRESH:
perf_counter_refresh(counter, arg);
break;
+ case PERF_COUNTER_IOC_RESET:
+ perf_counter_reset(counter);
+ break;
default:
err = -ENOTTY;
}