Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit dc82009a authored by Arnaldo Carvalho de Melo's avatar Arnaldo Carvalho de Melo
Browse files

perf record: No need to check for overwrites 



As we open the mmap with (PROT_READ | PROT_WRITE), signalling the kernel
with perf_mmap__write_tail() when consuming data, so the kernel will not
overwrite.

Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 54489c18

tools/perf/builtin-record.c

+3 −19
Original line number Diff line number Diff line
@@ -115,26 +115,10 @@ static void mmap_read(struct perf_mmap *md) 
	unsigned char *data = md->base + page_size;

	unsigned long size;

	void *buf;

	int diff;



	/*

	 * If we're further behind than half the buffer, there's a chance

	 * the writer will bite our tail and mess up the samples under us.

	 *

	 * If we somehow ended up ahead of the head, we got messed up.

	 *

	 * In either case, truncate and restart at head.

	 */

	diff = head - old;

	if (diff < 0) {

		fprintf(stderr, "WARNING: failed to keep up with mmap data\n");

		/*

		 * head points to a known good entry, start there.

		 */

		old = head;

	}

	if (old == head)

		return;



	if (old != head)

	samples++;



	size = head - old;