linux-kernel - RE: [PATCH V3 04/12] perf mmap: introduce perf_mmap__read

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Date:   Thu, 11 Jan 2018 21:27:20 +0000
From:   "Liang, Kan" <kan.liang@...el.com>
To:     Jiri Olsa <jolsa@...hat.com>
CC:     "acme@...nel.org" <acme@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "wangnan0@...wei.com" <wangnan0@...wei.com>,
        "jolsa@...nel.org" <jolsa@...nel.org>,
        "namhyung@...nel.org" <namhyung@...nel.org>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "yao.jin@...ux.intel.com" <yao.jin@...ux.intel.com>
Subject: RE: [PATCH V3 04/12] perf mmap: introduce perf_mmap__read_done

> On Thu, Dec 21, 2017 at 10:08:46AM -0800, kan.liang@...el.com wrote:
> > From: Kan Liang <kan.liang@...el.com>
> >
> > The direction of overwrite mode is backward. The last mmap__read_event
> > will set tail to map->prev. Need to correct the map->prev to head which
> > is the end of next read.
> >
> > It will be used later.
> >
> > Signed-off-by: Kan Liang <kan.liang@...el.com>
> > ---
> >  tools/perf/util/mmap.c | 11 +++++++++++
> >  tools/perf/util/mmap.h |  1 +
> >  2 files changed, 12 insertions(+)
> >
> > diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
> > index a844a2f..4aaeb64 100644
> > --- a/tools/perf/util/mmap.c
> > +++ b/tools/perf/util/mmap.c
> > @@ -343,3 +343,14 @@ int perf_mmap__push(struct perf_mmap *md,
> bool overwrite,
> >  out:
> >  	return rc;
> >  }
> > +
> > +/*
> > + * Mandatory for overwrite mode
> > + * The direction of overwrite mode is backward.
> > + * The last mmap__read_event will set tail to map->prev.
> 
> you mean perf_mmap__read function in this comment, right?
> 

Right.
Will fix it in V4.

Thanks,
Kan

> jirka
> 
> > + * Need to correct the map->prev to head which is the end of next read.
> > + */
> > +void perf_mmap__read_done(struct perf_mmap *map)
> > +{
> > +	map->prev = perf_mmap__read_head(map);
> > +}
> > diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h
> > index abe9b9f..2df27c1 100644
> > --- a/tools/perf/util/mmap.h
> > +++ b/tools/perf/util/mmap.h
> > @@ -96,4 +96,5 @@ size_t perf_mmap__mmap_len(struct perf_mmap
> *map);
> >
> >  int perf_mmap__read_init(struct perf_mmap *map, bool overwrite,
> >  			 u64 *start, u64 *end);
> > +void perf_mmap__read_done(struct perf_mmap *map);
> >  #endif /*__PERF_MMAP_H */
> > --
> > 2.5.5
> >