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SubjectRe: [PATCH] perf mmap: Discard head in overwrite_rb_find_range
Em Wed, Mar 07, 2018 at 11:21:57AM +0100, Jiri Olsa escreveu:
> On Tue, Mar 06, 2018 at 07:44:23PM +0800, 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.
>
> it conflicts a little with recent cleanup from Kan Liang,,
> https://marc.info/?t=152035082800001&r=1&w=2
>
> otherwise it looks ok to me

yeah, wait a while till I push Kan's simplifications and then resubmit,
ok?

- Arnaldo

> jirka
>
> >
> > Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
> > ---
> > 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 91531a7..6751ac9 100644
> > --- a/tools/perf/util/mmap.c
> > +++ b/tools/perf/util/mmap.c
> > @@ -223,19 +223,18 @@ 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;
> > @@ -287,7 +286,7 @@ int perf_mmap__read_init(struct perf_mmap *md, bool overwrite,
> > * 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, startp, endp))
> > + if (overwrite_rb_find_range(data, md->mask, startp, endp))
> > return -EINVAL;
> > }
> >
> > --
> > 1.7.12.4
> >

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