> Em Tue, Oct 10, 2017 at 10:20:15AM -0700, kan.li...@intel.com escreveu: > > From: Kan Liang <kan.li...@intel.com> > > > > Perf record can switch output. The new output should only store the > > data after switching. However, in overwrite backward mode, the new > > output still have the data from old output. > > > > At the end of mmap_read, the position of processed ring buffer is > > saved in md->prev. Next mmap_read should be end in md->prev. > > However, the md->prev is discarded. So next mmap_read has to process > > whole valid ring buffer, which definitely include the old processed > > data. > > > > Set the prev as the end of the range in backward mode. > > Do you think this should go together with the rest of this patchkit? > Probably it should be processed ASAP, i.e. perf/urgent, no? >
Hi Arnaldo, After some discussion, Wang Nan proposed a new patch to fix this issue. https://lkml.org/lkml/2017/10/12/441 I did some tests. It fixed the issue. Could you please take a look? If it's OK for you, I think it could be merged separately. Thanks, Kan > - Arnaldo > > > Signed-off-by: Kan Liang <kan.li...@intel.com> > > --- > > tools/perf/util/evlist.c | 14 +++++++++++++- > > 1 file changed, 13 insertions(+), 1 deletion(-) > > > > diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c index > > 33b8837..7d23cf5 100644 > > --- a/tools/perf/util/evlist.c > > +++ b/tools/perf/util/evlist.c > > @@ -742,13 +742,25 @@ static int > > rb_find_range(void *data, int mask, u64 head, u64 old, > > u64 *start, u64 *end, bool backward) { > > + int ret; > > + > > if (!backward) { > > *start = old; > > *end = head; > > return 0; > > } > > > > - return backward_rb_find_range(data, mask, head, start, end); > > + ret = backward_rb_find_range(data, mask, head, start, end); > > + > > + /* > > + * The start and end from backward_rb_find_range is the range for > all > > + * valid data in ring buffer. > > + * However, part of the data is processed previously. > > + * Reset the end to drop the processed data > > + */ > > + *end = old; > > + > > + return ret; > > } > > > > /* > > -- > > 2.5.5
