mirror of https://lore.kernel.org/lkml/
 help / color / mirror / Atom feed
* [PATCH] perf/core: Increase lost_samples count only for samples
@ 2022-09-02 18:19 Namhyung Kim
  2022-09-15 16:41 ` Namhyung Kim
  0 siblings, 1 reply; 2+ messages in thread
From: Namhyung Kim @ 2022-09-02 18:19 UTC (permalink / raw)
  To: Peter Zijlstra
  Cc: Ingo Molnar, Arnaldo Carvalho de Melo, Jiri Olsa, Mark Rutland,
	Alexander Shishkin, LKML, Stephane Eranian, Andi Kleen,
	Ian Rogers

The event->lost_samples count is intended to count (lost) sample records
but it's also counted for non-sample records like PERF_RECORD_MMAP etc.
This can be a problem when a sampling event tracks those side-band
events together.

As overflow handler for user events only calls perf_output_begin_
{for,back}ward() before writing to the ring buffer, we can pass an
additional flag to indicate that it's writing a sample record.

Fixes: 119a784c8127 ("perf/core: Add a new read format to get a number of lost samples")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 kernel/events/ring_buffer.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 726132039c38..5f38ee4edbdb 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -149,7 +149,7 @@ static __always_inline int
 __perf_output_begin(struct perf_output_handle *handle,
 		    struct perf_sample_data *data,
 		    struct perf_event *event, unsigned int size,
-		    bool backward)
+		    bool backward, bool sample)
 {
 	struct perf_buffer *rb;
 	unsigned long tail, offset, head;
@@ -174,7 +174,8 @@ __perf_output_begin(struct perf_output_handle *handle,
 	if (unlikely(rb->paused)) {
 		if (rb->nr_pages) {
 			local_inc(&rb->lost);
-			atomic64_inc(&event->lost_samples);
+			if (sample)
+				atomic64_inc(&event->lost_samples);
 		}
 		goto out;
 	}
@@ -256,7 +257,8 @@ __perf_output_begin(struct perf_output_handle *handle,
 
 fail:
 	local_inc(&rb->lost);
-	atomic64_inc(&event->lost_samples);
+	if (sample)
+		atomic64_inc(&event->lost_samples);
 	perf_output_put_handle(handle);
 out:
 	rcu_read_unlock();
@@ -268,14 +270,14 @@ int perf_output_begin_forward(struct perf_output_handle *handle,
 			      struct perf_sample_data *data,
 			      struct perf_event *event, unsigned int size)
 {
-	return __perf_output_begin(handle, data, event, size, false);
+	return __perf_output_begin(handle, data, event, size, false, true);
 }
 
 int perf_output_begin_backward(struct perf_output_handle *handle,
 			       struct perf_sample_data *data,
 			       struct perf_event *event, unsigned int size)
 {
-	return __perf_output_begin(handle, data, event, size, true);
+	return __perf_output_begin(handle, data, event, size, true, true);
 }
 
 int perf_output_begin(struct perf_output_handle *handle,
@@ -284,7 +286,7 @@ int perf_output_begin(struct perf_output_handle *handle,
 {
 
 	return __perf_output_begin(handle, data, event, size,
-				   unlikely(is_write_backward(event)));
+				   unlikely(is_write_backward(event)), false);
 }
 
 unsigned int perf_output_copy(struct perf_output_handle *handle,
-- 
2.37.2.789.g6183377224-goog


^ permalink raw reply	[flat|nested] 2+ messages in thread
end of thread, other threads:[~2022-09-15 16:41 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-09-02 18:19 [PATCH] perf/core: Increase lost_samples count only for samples Namhyung Kim
2022-09-15 16:41 ` Namhyung Kim

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®