perf: Fix wakeup storm for RO mmap()s (adb8e118) · Commits · 戴 / test

RO mmap()s don't update the tail pointer, so comparing against it for determining the written data size doesn't really do any good. Keep track of when we last did a wakeup, and compare against that. Signed-off-by:

Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Steven Rostedt <rostedt@goodmis.org> LKML-Reference: <20100521090710.684479310@chello.nl> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

include/linux/perf_event.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -599,7 +599,7 @@ struct perf_mmap_data {
		local_t head; /* write position */
		local_t nest; /* nested writers */
		local_t events; /* event limit */
		local_t wakeup; /* needs a wakeup */
		local_t wakeup; /* wakeup stamp */
		local_t lost; /* nr records lost */

		long watermark; /* wakeup watermark */

kernel/perf_event.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -3056,8 +3056,8 @@ int perf_output_begin(struct perf_output_handle *handle,
		handle->offset = offset;
		handle->head = head;

		if (head - tail > data->watermark)
		local_inc(&data->wakeup);
		if (head - local_read(&data->wakeup) > data->watermark)
		local_add(data->watermark, &data->wakeup);

		if (have_lost) {
		lost_event.header.type = PERF_RECORD_LOST;

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