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Commit 699db111 authored by Yisheng Xie's avatar Yisheng Xie Committed by Arnaldo Carvalho de Melo
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perf mmap: Discard head in overwrite_rb_find_range() 



In overwrite mode, start will be set to head in perf_mmap__read_init().
Therefore, there is no need to set the start one more time in
overwrite_rb_find_range() and *start can be used as head instead of
passing head to overwrite_rb_find_range().

Signed-off-by: default avatarYisheng Xie <xieyisheng1@huawei.com>
Reviewed-by: default avatarKan Liang <kan.liang@linux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1520944274-37001-1-git-send-email-xieyisheng1@huawei.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 9749adc3

tools/perf/util/mmap.c

+7 −8
Original line number Diff line number Diff line
@@ -199,19 +199,18 @@ int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd) 
	return 0;

}



static int overwrite_rb_find_range(void *buf, int mask, u64 head, u64 *start, u64 *end)

static int overwrite_rb_find_range(void *buf, int mask, u64 *start, u64 *end)

{

	struct perf_event_header *pheader;

	u64 evt_head = head;

	u64 evt_head = *start;

	int size = mask + 1;



	pr_debug2("overwrite_rb_find_range: buf=%p, head=%"PRIx64"\n", buf, head);

	pheader = (struct perf_event_header *)(buf + (head & mask));

	*start = head;

	pr_debug2("%s: buf=%p, start=%"PRIx64"\n", __func__, buf, *start);

	pheader = (struct perf_event_header *)(buf + (*start & mask));

	while (true) {

		if (evt_head - head >= (unsigned int)size) {

		if (evt_head - *start >= (unsigned int)size) {

			pr_debug("Finished reading overwrite ring buffer: rewind\n");

			if (evt_head - head > (unsigned int)size)

			if (evt_head - *start > (unsigned int)size)

				evt_head -= pheader->size;

			*end = evt_head;

			return 0;
@@ -262,7 +261,7 @@ int perf_mmap__read_init(struct perf_mmap *md) 
		 * Backward ring buffer is full. We still have a chance to read

		 * most of data from it.

		 */

		if (overwrite_rb_find_range(data, md->mask, head, &md->start, &md->end))

		if (overwrite_rb_find_range(data, md->mask, &md->start, &md->end))

			return -EINVAL;

	}