On 3/13/2018 8:31 AM, Yisheng Xie wrote:
In overwrite mode, start will be set to head in perf_mmap__read_init. Therefore, it is no need to set the start one more in overwrite_rb_find_range and *start can be used as head instead of passing head to overwrite_rb_find_range.
Looks good to me. Reviewed-by: Kan Liang <kan.li...@linux.intel.com> Thanks, Kan
Signed-off-by: Yisheng Xie <xieyishe...@huawei.com> --- v2: - rebase to perf/core tools/perf/util/mmap.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c index 074c4fd..38ca3ff 100644 --- a/tools/perf/util/mmap.c +++ b/tools/perf/util/mmap.c @@ -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; }
