From fa5881514ef9c9bcb29319aad85cf2d8889d91f1 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 18 May 2010 10:54:20 +0200 Subject: perf: Optimize the hotpath by converting the perf output buffer to local_t Since there is now only a single writer, we can use local_t instead and avoid all these pesky LOCK insn. Signed-off-by: Peter Zijlstra LKML-Reference: Signed-off-by: Ingo Molnar --- kernel/perf_event.c | 30 +++++++++++++++--------------- 1 file changed, 15 insertions(+), 15 deletions(-) (limited to 'kernel/perf_event.c') diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 8cf737da3ec4..1f98c78c3343 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -2916,7 +2916,7 @@ static void perf_output_get_handle(struct perf_output_handle *handle) struct perf_mmap_data *data = handle->data; preempt_disable(); - atomic_inc(&data->nest); + local_inc(&data->nest); } static void perf_output_put_handle(struct perf_output_handle *handle) @@ -2925,13 +2925,13 @@ static void perf_output_put_handle(struct perf_output_handle *handle) unsigned long head; again: - head = atomic_long_read(&data->head); + head = local_read(&data->head); /* * IRQ/NMI can happen here, which means we can miss a head update. */ - if (!atomic_dec_and_test(&data->nest)) + if (!local_dec_and_test(&data->nest)) return; /* @@ -2945,12 +2945,12 @@ again: * Now check if we missed an update, rely on the (compiler) * barrier in atomic_dec_and_test() to re-read data->head. */ - if (unlikely(head != atomic_long_read(&data->head))) { - atomic_inc(&data->nest); + if (unlikely(head != local_read(&data->head))) { + local_inc(&data->nest); goto again; } - if (atomic_xchg(&data->wakeup, 0)) + if (local_xchg(&data->wakeup, 0)) perf_output_wakeup(handle); preempt_enable(); @@ -3031,7 +3031,7 @@ int perf_output_begin(struct perf_output_handle *handle, if (!data->nr_pages) goto out; - have_lost = atomic_read(&data->lost); + have_lost = local_read(&data->lost); if (have_lost) size += sizeof(lost_event); @@ -3045,24 +3045,24 @@ int perf_output_begin(struct perf_output_handle *handle, */ tail = ACCESS_ONCE(data->user_page->data_tail); smp_rmb(); - offset = head = atomic_long_read(&data->head); + offset = head = local_read(&data->head); head += size; if (unlikely(!perf_output_space(data, tail, offset, head))) goto fail; - } while (atomic_long_cmpxchg(&data->head, offset, head) != offset); + } while (local_cmpxchg(&data->head, offset, head) != offset); handle->offset = offset; handle->head = head; if (head - tail > data->watermark) - atomic_inc(&data->wakeup); + local_inc(&data->wakeup); if (have_lost) { lost_event.header.type = PERF_RECORD_LOST; lost_event.header.misc = 0; lost_event.header.size = sizeof(lost_event); lost_event.id = event->id; - lost_event.lost = atomic_xchg(&data->lost, 0); + lost_event.lost = local_xchg(&data->lost, 0); perf_output_put(handle, lost_event); } @@ -3070,7 +3070,7 @@ int perf_output_begin(struct perf_output_handle *handle, return 0; fail: - atomic_inc(&data->lost); + local_inc(&data->lost); perf_output_put_handle(handle); out: rcu_read_unlock(); @@ -3086,10 +3086,10 @@ void perf_output_end(struct perf_output_handle *handle) int wakeup_events = event->attr.wakeup_events; if (handle->sample && wakeup_events) { - int events = atomic_inc_return(&data->events); + int events = local_inc_return(&data->events); if (events >= wakeup_events) { - atomic_sub(wakeup_events, &data->events); - atomic_inc(&data->wakeup); + local_sub(wakeup_events, &data->events); + local_inc(&data->wakeup); } } -- cgit v1.2.3