Messages in this thread | | | Subject | Re: [PATCH v2 -perf/core 1/2] perf mmap: Discard head in overwrite_rb_find_range | From | "Liang, Kan" <> | Date | Fri, 16 Mar 2018 10:16:53 -0400 |
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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.liang@linux.intel.com>
Thanks, Kan
> Signed-off-by: Yisheng Xie <xieyisheng1@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; > } > >
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