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perf_counter: counter overflow limit

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Provide means to auto-disable the counter after 'n' overflow events.

Create the counter with hw_event.disabled = 1, and then issue an
ioctl(fd, PREF_COUNTER_IOC_REFRESH, n); to set the limit and enable
the counter.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090406094518.083139737@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-04-06 11:45:07 +02:00 • committed by Ingo Molnar
commit 79f1464156
2 changed files with 50 additions and 13 deletions
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12
include/linux/perf_counter.h
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@ -155,8 +155,9 @@ struct perf_counter_hw_event {
/*
* Ioctls that can be done on a perf counter fd:
*/
#define PERF_COUNTER_IOC_ENABLE _IO('$', 0)
#define PERF_COUNTER_IOC_DISABLE _IO('$', 1)
#define PERF_COUNTER_IOC_ENABLE _IO ('$', 0)
#define PERF_COUNTER_IOC_DISABLE _IO ('$', 1)
#define PERF_COUNTER_IOC_REFRESH _IOW('$', 2, u32)
/*
* Structure of the page that can be mapped via mmap
@ -403,9 +404,14 @@ struct perf_counter {
/* poll related */
wait_queue_head_t waitq;
struct fasync_struct *fasync;
/* optional: for NMIs */
/* delayed work for NMIs and such */
int pending_wakeup;
int pending_disable;
struct perf_pending_entry pending;
atomic_t event_limit;
void (*destroy)(struct perf_counter *);
struct rcu_head rcu_head;
#endif