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perf_counter: add ioctl(PERF_COUNTER_IOC_RESET)

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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>
This commit is contained in:
Peter Zijlstra 2009-05-05 17:50:23 +02:00 committed by Ingo Molnar
parent c66de4a5be
commit 6de6a7b957
2 changed files with 9 additions and 0 deletions
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1
include/linux/perf_counter.h
View file

@ -160,6 +160,7 @@ struct perf_counter_hw_event {
#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

8
kernel/perf_counter.c
View file

@ -1288,6 +1288,11 @@ static unsigned int perf_poll(struct file *file, poll_table *wait)
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 @@ static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
case PERF_COUNTER_IOC_REFRESH:
perf_counter_refresh(counter, arg);
break;
case PERF_COUNTER_IOC_RESET:
perf_counter_reset(counter);
break;
default:
err = -ENOTTY;
}