perf: Add wakeup watermark control to the AUX area
When AUX area gets a certain amount of new data, we want to wake up
userspace to collect it. This adds a new control to specify how much
data will cause a wakeup. This is then passed down to pmu drivers via
output handle's "wakeup" field, so that the driver can find the nearest
point where it can generate an interrupt.
We repurpose __reserved_2 in the event attribute for this, even though
it was never checked to be zero before, aux_watermark will only matter
for new AUX-aware code, so the old code should still be fine.
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kaixu Xia <kaixu.xia@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Robert Richter <rric@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@infradead.org
Cc: adrian.hunter@intel.com
Cc: kan.liang@intel.com
Cc: markus.t.metzger@intel.com
Cc: mathieu.poirier@linaro.org
Link: http://lkml.kernel.org/r/1421237903-181015-10-git-send-email-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 81e8d14..31f6b50 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4677,7 +4677,8 @@
perf_event_init_userpage(event);
perf_event_update_userpage(event);
} else {
- ret = rb_alloc_aux(rb, event, vma->vm_pgoff, nr_pages, flags);
+ ret = rb_alloc_aux(rb, event, vma->vm_pgoff, nr_pages,
+ event->attr.aux_watermark, flags);
if (!ret)
rb->aux_mmap_locked = extra;
}
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index ffd51d9..9f6ce9ba 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -27,6 +27,7 @@
local_t lost; /* nr records lost */
long watermark; /* wakeup watermark */
+ long aux_watermark;
/* poll crap */
spinlock_t event_lock;
struct list_head event_list;
@@ -38,6 +39,7 @@
/* AUX area */
local_t aux_head;
local_t aux_nest;
+ local_t aux_wakeup;
unsigned long aux_pgoff;
int aux_nr_pages;
int aux_overwrite;
@@ -57,7 +59,7 @@
rb_alloc(int nr_pages, long watermark, int cpu, int flags);
extern void perf_event_wakeup(struct perf_event *event);
extern int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,
- pgoff_t pgoff, int nr_pages, int flags);
+ pgoff_t pgoff, int nr_pages, long watermark, int flags);
extern void rb_free_aux(struct ring_buffer *rb);
extern struct ring_buffer *ring_buffer_get(struct perf_event *event);
extern void ring_buffer_put(struct ring_buffer *rb);
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 67b3283..232f00f 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -296,6 +296,7 @@
*/
if (!rb->aux_overwrite) {
aux_tail = ACCESS_ONCE(rb->user_page->aux_tail);
+ handle->wakeup = local_read(&rb->aux_wakeup) + rb->aux_watermark;
if (aux_head - aux_tail < perf_aux_size(rb))
handle->size = CIRC_SPACE(aux_head, aux_tail, perf_aux_size(rb));
@@ -359,9 +360,12 @@
perf_event_aux_event(handle->event, aux_head, size, flags);
}
- rb->user_page->aux_head = local_read(&rb->aux_head);
+ aux_head = rb->user_page->aux_head = local_read(&rb->aux_head);
- perf_output_wakeup(handle);
+ if (aux_head - local_read(&rb->aux_wakeup) >= rb->aux_watermark) {
+ perf_output_wakeup(handle);
+ local_add(rb->aux_watermark, &rb->aux_wakeup);
+ }
handle->event = NULL;
local_set(&rb->aux_nest, 0);
@@ -383,6 +387,14 @@
local_add(size, &rb->aux_head);
+ aux_head = rb->user_page->aux_head = local_read(&rb->aux_head);
+ if (aux_head - local_read(&rb->aux_wakeup) >= rb->aux_watermark) {
+ perf_output_wakeup(handle);
+ local_add(rb->aux_watermark, &rb->aux_wakeup);
+ handle->wakeup = local_read(&rb->aux_wakeup) +
+ rb->aux_watermark;
+ }
+
handle->head = aux_head;
handle->size -= size;
@@ -433,7 +445,7 @@
}
int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,
- pgoff_t pgoff, int nr_pages, int flags)
+ pgoff_t pgoff, int nr_pages, long watermark, int flags)
{
bool overwrite = !(flags & RING_BUFFER_WRITABLE);
int node = (event->cpu == -1) ? -1 : cpu_to_node(event->cpu);
@@ -497,6 +509,10 @@
atomic_set(&rb->aux_refcount, 1);
rb->aux_overwrite = overwrite;
+ rb->aux_watermark = watermark;
+
+ if (!rb->aux_watermark && !rb->aux_overwrite)
+ rb->aux_watermark = nr_pages << (PAGE_SHIFT - 1);
out:
if (!ret)
