linux-kernel - Re: [PATCH v1] perf inject: Fix leader sampling inserting additional samples

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Message-ID: <CAP-5=fXN4y++hD-TzVToobrmH73V_h1fbGq+DuZxmgi=jF5NWQ@mail.gmail.com>
Date: Mon, 12 Aug 2024 13:37:36 -0700
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, 
	linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org, 
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v1] perf inject: Fix leader sampling inserting additional samples

On Wed, Jul 31, 2024 at 11:21 AM Namhyung Kim <namhyung@...nel.org> wrote:
>
> Hi Ian,
>
> On Mon, Jul 29, 2024 at 03:06:20PM -0700, Ian Rogers wrote:
> > The processing of leader samples would turn an individual sample with
> > a group of read values into multiple samples. Perf inject would pass
> > through the additional samples increasing the output data file size:
> >
> > ```
> > $ perf record -g -e "{instructions,cycles}:S" -o perf.orig.data true
> > $ perf script -D -i perf.orig.data | sed -e 's/perf.orig.data/perf.data/g' > orig.txt
> > $ perf inject -i perf.orig.data -o perf.new.data
> > $ perf script -D -i perf.new.data | sed -e 's/perf.new.data/perf.data/g' > new.txt
> > $ diff -u orig.txt new.txt
> > --- orig.txt    2024-07-29 14:29:40.606576769 -0700
> > +++ new.txt     2024-07-29 14:30:04.142737434 -0700
> > ...
> > -0xc550@...f.data [0x30]: event: 3
> > +0xc550@...f.data [0xd0]: event: 9
> > +.
> > +. ... raw event: size 208 bytes
> > +.  0000:  09 00 00 00 01 00 d0 00 fc 72 01 86 ff ff ff ff  .........r......
> > +.  0010:  74 7d 2c 00 74 7d 2c 00 fb c3 79 f9 ba d5 05 00  t},.t},...y.....
> > +.  0020:  e6 cb 1a 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
> > +.  0030:  02 00 00 00 00 00 00 00 76 01 00 00 00 00 00 00  ........v.......
> > +.  0040:  e6 cb 1a 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> > +.  0050:  62 18 00 00 00 00 00 00 f6 cb 1a 00 00 00 00 00  b...............
> > +.  0060:  00 00 00 00 00 00 00 00 0c 00 00 00 00 00 00 00  ................
> > +.  0070:  80 ff ff ff ff ff ff ff fc 72 01 86 ff ff ff ff  .........r......
> > +.  0080:  f3 0e 6e 85 ff ff ff ff 0c cb 7f 85 ff ff ff ff  ..n.............
> > +.  0090:  bc f2 87 85 ff ff ff ff 44 af 7f 85 ff ff ff ff  ........D.......
> > +.  00a0:  bd be 7f 85 ff ff ff ff 26 d0 7f 85 ff ff ff ff  ........&.......
> > +.  00b0:  6d a4 ff 85 ff ff ff ff ea 00 20 86 ff ff ff ff  m......... .....
> > +.  00c0:  00 fe ff ff ff ff ff ff 57 14 4f 43 fc 7e 00 00  ........W.OC.~..
> > +
> > +1642373909693435 0xc550 [0xd0]: PERF_RECORD_SAMPLE(IP, 0x1): 2915700/2915700: 0xffffffff860172fc period: 1 addr: 0
> > +... FP chain: nr:12
> > +.....  0: ffffffffffffff80
> > +.....  1: ffffffff860172fc
> > +.....  2: ffffffff856e0ef3
> > +.....  3: ffffffff857fcb0c
> > +.....  4: ffffffff8587f2bc
> > +.....  5: ffffffff857faf44
> > +.....  6: ffffffff857fbebd
> > +.....  7: ffffffff857fd026
> > +.....  8: ffffffff85ffa46d
> > +.....  9: ffffffff862000ea
> > +..... 10: fffffffffffffe00
> > +..... 11: 00007efc434f1457
> > +... sample_read:
> > +.... group nr 2
> > +..... id 00000000001acbe6, value 0000000000000176, lost 0
> > +..... id 00000000001acbf6, value 0000000000001862, lost 0
> > +
> > +0xc620@...f.data [0x30]: event: 3
> > ...
> > ```
> >
> > This behavior is incorrect as in the case above perf inject should
> > have done nothing. Fix this behavior by disabling separating samples
> > for a tool that requests it. Only request this for `perf inject` so as
> > to not affect other perf tools. With the patch and the test above
> > there are no differences between the orig.txt and new.txt.
> >
> > Fixes: e4caec0d1af3 ("perf evsel: Add PERF_SAMPLE_READ sample related processing")
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
>
> Acked-by: Namhyung Kim <namhyung@...nel.org>

Ping.

Thanks,
Ian