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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
parent 339f7c90b8
commit 79f1464156
2 changed files with 50 additions and 13 deletions
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12
include/linux/perf_counter.h
View File

@ -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

51
kernel/perf_counter.c
View File

@ -744,6 +744,12 @@ static void perf_counter_enable(struct perf_counter *counter)
spin_unlock_irq(&ctx->lock);
}
static void perf_counter_refresh(struct perf_counter *counter, int refresh)
{
atomic_add(refresh, &counter->event_limit);
perf_counter_enable(counter);
}
/*
* Enable a counter and all its children.
*/
@ -1311,6 +1317,9 @@ static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
case PERF_COUNTER_IOC_DISABLE:
perf_counter_disable_family(counter);
break;
case PERF_COUNTER_IOC_REFRESH:
perf_counter_refresh(counter, arg);
break;
default:
err = -ENOTTY;
}
@ -1590,14 +1599,6 @@ void perf_counter_wakeup(struct perf_counter *counter)
kill_fasync(&counter->fasync, SIGIO, POLL_IN);
}
static void perf_pending_wakeup(struct perf_pending_entry *entry)
{
struct perf_counter *counter = container_of(entry,
struct perf_counter, pending);
perf_counter_wakeup(counter);
}
/*
* Pending wakeups
*
@ -1607,6 +1608,22 @@ static void perf_pending_wakeup(struct perf_pending_entry *entry)
* single linked list and use cmpxchg() to add entries lockless.
*/
static void perf_pending_counter(struct perf_pending_entry *entry)
{
struct perf_counter *counter = container_of(entry,
struct perf_counter, pending);
if (counter->pending_disable) {
counter->pending_disable = 0;
perf_counter_disable(counter);
}
if (counter->pending_wakeup) {
counter->pending_wakeup = 0;
perf_counter_wakeup(counter);
}
}
#define PENDING_TAIL ((struct perf_pending_entry *)-1UL)
static DEFINE_PER_CPU(struct perf_pending_entry *, perf_pending_head) = {
@ -1715,8 +1732,9 @@ struct perf_output_handle {
static inline void __perf_output_wakeup(struct perf_output_handle *handle)
{
if (handle->nmi) {
handle->counter->pending_wakeup = 1;
perf_pending_queue(&handle->counter->pending,
perf_pending_wakeup);
perf_pending_counter);
} else
perf_counter_wakeup(handle->counter);
}
@ -2063,8 +2081,21 @@ void perf_counter_munmap(unsigned long addr, unsigned long len,
int perf_counter_overflow(struct perf_counter *counter,
int nmi, struct pt_regs *regs)
{
int events = atomic_read(&counter->event_limit);
int ret = 0;
if (events && atomic_dec_and_test(&counter->event_limit)) {
ret = 1;
if (nmi) {
counter->pending_disable = 1;
perf_pending_queue(&counter->pending,
perf_pending_counter);
} else
perf_counter_disable(counter);
}
perf_counter_output(counter, nmi, regs);
return 0;
return ret;
}
/*