linux-kernel - Re: [PATCH] perf diff: bug fix, donot overwrite valid build id

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Message-ID: <20161219183758.GC551@kernel.org>
Date:   Mon, 19 Dec 2016 15:37:58 -0300
From:   "acme@...nel.org" <acme@...nel.org>
To:     "Liang, Kan" <kan.liang@...el.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dima@...retsauce.net" <dima@...retsauce.net>,
        "jolsa@...hat.com" <jolsa@...hat.com>,
        "namhyung@...nel.org" <namhyung@...nel.org>,
        "andi@...stfloor.org" <andi@...stfloor.org>
Subject: Re: [PATCH] perf diff: bug fix, donot overwrite valid build id

Em Mon, Dec 19, 2016 at 02:53:30PM +0000, Liang, Kan escreveu:
> Hi Arnaldo,
> 
> Ping
> 
> Are you OK with the fix?

Yeah, looks ok, will merge it.

- Arnaldo
 
> Thanks,
> Kan
> 
> > 
> > From: Kan Liang <kan.liang@...el.com>
> > 
> > Fixes a perf diff regression issue which was introduced by commit
> > 5baecbcd9c9a ("perf symbols: we can now read separate debug-info files
> > based on a build ID")
> > 
> > The binary name could be same when perf diff different binaries. Build id is
> > used to distinguish between them.
> > However, the previous patch assumes the same binary name has same
> > build id. So it overwrites the build id according to the binary name,
> > regardless of whether the build id is set or not.
> > 
> > Check the has_build_id in dso__load. If the build id is already set, use it.
> > 
> > Before the fix applies,
> >  sudo ./perf diff 1.perf.data 2.perf.data  # Event 'cycles'
> >  #
> >  # Baseline    Delta  Shared Object     Symbol
> >  # ........  .......  ................  .............................
> >  #
> >     99.83%  -99.80%  tchain_edit       [.] f2
> >      0.12%  +99.81%  tchain_edit       [.] f3
> >      0.02%   -0.01%  [ixgbe]           [k] ixgbe_read_reg
> > 
> > After the fix applies,
> >  sudo ./perf diff 1.perf.data 2.perf.data  # Event 'cycles'
> >  #
> >  # Baseline    Delta  Shared Object     Symbol
> >  # ........  .......  ................  .............................
> >  #
> >     99.83%   +0.10%  tchain_edit       [.] f3
> >      0.12%   -0.08%  tchain_edit       [.] f2
> > 
> > Signed-off-by: Kan Liang <kan.liang@...el.com>
> > ---
> >  tools/perf/util/symbol.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c index
> > df2482b..dc93940 100644
> > --- a/tools/perf/util/symbol.c
> > +++ b/tools/perf/util/symbol.c
> > @@ -1459,7 +1459,8 @@ int dso__load(struct dso *dso, struct map *map)
> >  	 * Read the build id if possible. This is required for
> >  	 * DSO_BINARY_TYPE__BUILDID_DEBUGINFO to work
> >  	 */
> > -	if (is_regular_file(dso->long_name) &&
> > +	if (!dso->has_build_id &&
> > +	    is_regular_file(dso->long_name) &&
> >  	    filename__read_build_id(dso->long_name, build_id,
> > BUILD_ID_SIZE) > 0)
> >  		dso__set_build_id(dso, build_id);
> > 
> > --
> > 2.4.3