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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@perf.data [0x30]: event: 3
+0xc550@perf.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@perf.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: e4caec0d1a ("perf evsel: Add PERF_SAMPLE_READ sample related processing")
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240729220620.2957754-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.