Messages in this thread | | | Date | Thu, 11 Jan 2018 15:25:32 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH V3 03/12] perf mmap: discard 'prev' in perf_mmap__read |
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On Thu, Dec 21, 2017 at 10:08:45AM -0800, kan.liang@intel.com wrote: > From: Kan Liang <kan.liang@intel.com> > > 'start' and 'prev' are duplicate in perf_mmap__read() > > Use 'map->prev' to replace 'start' in perf_mmap__read_*(). > > Suggested-by: Wang Nan <wangnan0@huawei.com> > Signed-off-by: Kan Liang <kan.liang@intel.com> > --- > tools/perf/util/mmap.c | 28 ++++++++++------------------ > 1 file changed, 10 insertions(+), 18 deletions(-) > > diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c > index 3fd4f3c..a844a2f 100644 > --- a/tools/perf/util/mmap.c > +++ b/tools/perf/util/mmap.c > @@ -22,29 +22,27 @@ size_t perf_mmap__mmap_len(struct perf_mmap *map) > > /* When check_messup is true, 'end' must points to a good entry */ > static union perf_event *perf_mmap__read(struct perf_mmap *map, > - u64 start, u64 end, u64 *prev) > + u64 *start, u64 end) > { > unsigned char *data = map->base + page_size; > union perf_event *event = NULL; > - int diff = end - start; > + int diff = end - *start;
I'd like more if the arg was pointer, like 'u64 *startp' and you kept using the 'u64 start' value in the body.. but can't see any technical benefit behind it to force it ;-)
jirka
> > if (diff >= (int)sizeof(event->header)) { > size_t size; > > - event = (union perf_event *)&data[start & map->mask]; > + event = (union perf_event *)&data[*start & map->mask]; > size = event->header.size; > > - if (size < sizeof(event->header) || diff < (int)size) { > - event = NULL; > - goto broken_event; > - } > + if (size < sizeof(event->header) || diff < (int)size) > + return NULL; > > /* > * Event straddles the mmap boundary -- header should always > * be inside due to u64 alignment of output. > */ > - if ((start & map->mask) + size != ((start + size) & map->mask)) { > - unsigned int offset = start; > + if ((*start & map->mask) + size != ((*start + size) & map->mask)) { > + unsigned int offset = *start; > unsigned int len = min(sizeof(*event), size), cpy; > void *dst = map->event_copy; > > @@ -59,20 +57,15 @@ static union perf_event *perf_mmap__read(struct perf_mmap *map, > event = (union perf_event *)map->event_copy; > } > > - start += size; > + *start += size; > } > > -broken_event: > - if (prev) > - *prev = start; > - > return event; > }
SNIP
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