From 79f146415623fe74f39af67c0f6adc208939a410 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 6 Apr 2009 11:45:07 +0200 Subject: [PATCH] perf_counter: counter overflow limit 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 Cc: Paul Mackerras Cc: Corey Ashford LKML-Reference: <20090406094518.083139737@chello.nl> Signed-off-by: Ingo Molnar --- include/linux/perf_counter.h | 12 ++++++--- kernel/perf_counter.c | 51 +++++++++++++++++++++++++++++------- 2 files changed, 50 insertions(+), 13 deletions(-) diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h index 928a7fae0961..ef4dcbff75ab 100644 --- a/include/linux/perf_counter.h +++ b/include/linux/perf_counter.h @@ -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 diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index 19990d1f0215..c05e10354bc9 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -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; } /* -- 2.34.1