diff options
| -rw-r--r-- | include/linux/perf_counter.h | 10 | ||||
| -rw-r--r-- | kernel/perf_counter.c | 32 |
2 files changed, 27 insertions, 15 deletions
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h index 972f90d..6c1ef72 100644 --- a/include/linux/perf_counter.h +++ b/include/linux/perf_counter.h @@ -199,10 +199,14 @@ struct perf_counter_attr { inherit_stat : 1, /* per task counts */ enable_on_exec : 1, /* next exec enables */ task : 1, /* trace fork/exit */ + watermark : 1, /* wakeup_watermark */ - __reserved_1 : 50; + __reserved_1 : 49; - __u32 wakeup_events; /* wakeup every n events */ + union { + __u32 wakeup_events; /* wakeup every n events */ + __u32 wakeup_watermark; /* bytes before wakeup */ + }; __u32 __reserved_2; __u64 __reserved_3; @@ -521,6 +525,8 @@ struct perf_mmap_data { atomic_t wakeup; /* needs a wakeup */ atomic_t lost; /* nr records lost */ + long watermark; /* wakeup watermark */ + struct perf_counter_mmap_page *user_page; void *data_pages[0]; }; diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index fe0d1ad..29b73b6 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -2176,6 +2176,13 @@ static int perf_mmap_data_alloc(struct perf_counter *counter, int nr_pages) data->nr_pages = nr_pages; atomic_set(&data->lock, -1); + if (counter->attr.watermark) { + data->watermark = min_t(long, PAGE_SIZE * nr_pages, + counter->attr.wakeup_watermark); + } + if (!data->watermark) + data->watermark = max(PAGE_SIZE, PAGE_SIZE * nr_pages / 4); + rcu_assign_pointer(counter->data, data); return 0; @@ -2517,23 +2524,15 @@ struct perf_output_handle { unsigned long flags; }; -static bool perf_output_space(struct perf_mmap_data *data, - unsigned int offset, unsigned int head) +static bool perf_output_space(struct perf_mmap_data *data, unsigned long tail, + unsigned long offset, unsigned long head) { - unsigned long tail; unsigned long mask; if (!data->writable) return true; mask = (data->nr_pages << PAGE_SHIFT) - 1; - /* - * Userspace could choose to issue a mb() before updating the tail - * pointer. So that all reads will be completed before the write is - * issued. - */ - tail = ACCESS_ONCE(data->user_page->data_tail); - smp_rmb(); offset = (offset - tail) & mask; head = (head - tail) & mask; @@ -2679,7 +2678,7 @@ static int perf_output_begin(struct perf_output_handle *handle, { struct perf_counter *output_counter; struct perf_mmap_data *data; - unsigned int offset, head; + unsigned long tail, offset, head; int have_lost; struct { struct perf_event_header header; @@ -2717,16 +2716,23 @@ static int perf_output_begin(struct perf_output_handle *handle, perf_output_lock(handle); do { + /* + * Userspace could choose to issue a mb() before updating the + * tail pointer. So that all reads will be completed before the + * write is issued. + */ + tail = ACCESS_ONCE(data->user_page->data_tail); + smp_rmb(); offset = head = atomic_long_read(&data->head); head += size; - if (unlikely(!perf_output_space(data, offset, head))) + if (unlikely(!perf_output_space(data, tail, offset, head))) goto fail; } while (atomic_long_cmpxchg(&data->head, offset, head) != offset); handle->offset = offset; handle->head = head; - if ((offset >> PAGE_SHIFT) != (head >> PAGE_SHIFT)) + if (head - tail > data->watermark) atomic_set(&data->wakeup, 1); if (have_lost) { |
