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504c1ad116
Implemented -z,--compression_level[=<n>] option that enables compression
of mmaped kernel data buffers content in runtime during perf record mode
collection. Default option value is 1 (fastest compression).
Compression overhead has been measured for serial and AIO streaming when
profiling matrix multiplication workload:
-------------------------------------------------------------
| SERIAL | AIO-1 |
----------------------------------------------------------------|
|-z | OVH(x) | ratio(x) size(MiB) | OVH(x) | ratio(x) size(MiB) |
|---------------------------------------------------------------|
| 0 | 1,00 | 1,000 179,424 | 1,00 | 1,000 187,527 |
| 1 | 1,04 | 8,427 181,148 | 1,01 | 8,474 188,562 |
| 2 | 1,07 | 8,055 186,953 | 1,03 | 7,912 191,773 |
| 3 | 1,04 | 8,283 181,908 | 1,03 | 8,220 191,078 |
| 5 | 1,09 | 8,101 187,705 | 1,05 | 7,780 190,065 |
| 8 | 1,05 | 9,217 179,191 | 1,12 | 6,111 193,024 |
-----------------------------------------------------------------
OVH = (Execution time with -z N) / (Execution time with -z 0)
ratio - compression ratio
size - number of bytes that was compressed
size ~= trace size x ratio
Committer notes:
Testing it I noticed that it failed to disable build id processing when
compression is enabled, and as we'd have to uncompress everything to
look for the PERF_RECORD_{MMAP,SAMPLE,etc} to figure out which build ids
to read from DSOs, we better disable build id processing when
compression is enabled, logging with pr_debug() when doing so:
Original patch:
# perf record -z2
^C[ perf record: Woken up 1 times to write data ]
0x1746e0 [0x76]: failed to process type: 81 [Invalid argument]
[ perf record: Captured and wrote 1.568 MB perf.data, compressed (original 0.452 MB, ratio is 3.995) ]
#
After auto-disabling build id processing when compression is enabled:
$ perf record -z2 sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.001 MB perf.data, compressed (original 0.001 MB, ratio is 2.292) ]
$ perf record -v -z2 sleep 1
Compression enabled, disabling build id collection at the end of the session.
<SNIP extra -v pr_debug() messages>
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.001 MB perf.data, compressed (original 0.001 MB, ratio is 2.305) ]
$
Also, with parts of the patch originally after this one moved to just
before this one we get:
$ perf record -z2 sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.001 MB perf.data, compressed (original 0.001 MB, ratio is 2.371) ]
$ perf report -D | grep COMPRESS
0 0x1b8 [0x155]: PERF_RECORD_COMPRESSED: unhandled!
0 0x30d [0x80]: PERF_RECORD_COMPRESSED: unhandled!
COMPRESSED events: 2
COMPRESSED events: 0
$
I.e. when faced with PERF_RECORD_COMPRESSED that we still have no code
to process, we just show it as not being handled, skip them and
continue, while before we had:
$ perf report -D | grep COMPRESS
0x1b8 [0x169]: failed to process type: 81 [Invalid argument]
Error:
failed to process sample
0 0x1b8 [0x169]: PERF_RECORD_COMPRESSED
$
Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/9ff06518-ae63-a908-e44d-5d9e56dd66d9@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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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 Restructured Text 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.