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Alexey Budankov 504c1ad116 perf record: Implement -z,--compression_level[=<n>] option
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>
2019-05-15 16:36:49 -03:00
Documentation * amd64_edac: Family 0x17, models 0x30-.. enablement (Yazen Ghannam) 2019-05-06 19:53:11 -07:00
LICENSES LICENSES: Add GCC runtime library exception text 2019-01-16 14:54:15 -07:00
arch perf/x86/intel: Fix INTEL_FLAGS_EVENT_CONSTRAINT* masking 2019-05-10 08:04:17 +02:00
block bfq: update internal depth state when queue depth changes 2019-04-13 19:08:22 -06:00
certs kexec, KEYS: Make use of platform keyring for signature verify 2019-02-04 17:34:07 -05:00
crypto crypto: lrw - Fix atomic sleep when walking skcipher 2019-04-18 22:13:46 +08:00
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security s390 updates for the 5.2 merge window 2019-05-06 16:42:54 -07:00
sound ACPI updates for 5.2-rc1 2019-05-06 19:35:13 -07:00
tools perf record: Implement -z,--compression_level[=<n>] option 2019-05-15 16:36:49 -03:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt arm64 updates for 5.2 2019-05-06 17:54:22 -07:00
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CREDITS Char/Misc driver patches for 5.1-rc1 2019-03-06 14:18:59 -08:00
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MAINTAINERS Merge branch 'ras-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-05-06 19:54:57 -07:00
Makefile Linux 5.1 2019-05-05 17:42:58 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README

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.