linux/tools/lib/api
Ian Rogers 53df2b9344 libsymbols kallsyms: Parse using io api
'perf record' will call kallsyms__parse 4 times during startup and
process megabytes of data. This changes kallsyms__parse to use the io
library rather than fgets to improve performance of the user code by
over 8%.

Before:

  Running 'internals/kallsyms-parse' benchmark:
  Average kallsyms__parse took: 103.988 ms (+- 0.203 ms)

After:

  Running 'internals/kallsyms-parse' benchmark:
  Average kallsyms__parse took: 95.571 ms (+- 0.006 ms)

For a workload like:

  $ perf record /bin/true
  Run under 'perf record -e cycles:u -g' the time goes from:
  Before
  30.10%     1.67%  perf     perf                [.] kallsyms__parse
  After
  25.55%    20.04%  perf     perf                [.] kallsyms__parse

So a little under 5% of the start-up time is removed. A lot of what
remains is on the kernel side, but caching kallsyms within perf would at
least impact memory footprint.

Committer notes:

The internal/kallsyms-parse bench is run using:

  [root@five ~]# perf bench internals kallsyms-parse
  # Running 'internals/kallsyms-parse' benchmark:
    Average kallsyms__parse took: 80.381 ms (+- 0.115 ms)
  [root@five ~]#

And this pre-existing test uses these routines to parse kallsyms and
then compare with the info obtained from the matching ELF symtab:

  [root@five ~]# perf test vmlinux
   1: vmlinux symtab matches kallsyms                       : Ok
  [root@five ~]#

Also we can't remove hex2u64() in this patch as this breaks the build:

  /usr/bin/ld: /tmp/build/perf/perf-in.o: in function `modules__parse':
  /home/acme/git/perf/tools/perf/util/symbol.c:607: undefined reference to `hex2u64'
  /usr/bin/ld: /home/acme/git/perf/tools/perf/util/symbol.c:607: undefined reference to `hex2u64'
  /usr/bin/ld: /tmp/build/perf/perf-in.o: in function `dso__load_perf_map':
  /home/acme/git/perf/tools/perf/util/symbol.c:1477: undefined reference to `hex2u64'
  /usr/bin/ld: /home/acme/git/perf/tools/perf/util/symbol.c:1483: undefined reference to `hex2u64'
  collect2: error: ld returned 1 exit status

Leave it there, move it in the next patch.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lore.kernel.org/lkml/20200501221315.54715-3-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-05-05 16:35:32 -03:00
..
fd treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 251 2019-06-05 17:30:26 +02:00
fs tools api fs: Make xxx__mountpoint() more scalable 2020-04-16 12:19:12 -03:00
Build tools lib api: Add str_error_c to libapi 2016-07-27 17:16:43 -03:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
cpu.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
cpu.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
debug-internal.h tools lib api: Renaming pr_warning to pr_warn 2019-10-18 15:02:57 +02:00
debug.c tools lib api: Renaming pr_warning to pr_warn 2019-10-18 15:02:57 +02:00
debug.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
io.h libsymbols kallsyms: Parse using io api 2020-05-05 16:35:32 -03:00