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The sysfs format files are loaded eagerly in a PMU. Add a flag so that
we create the format but only load the contents when necessary.
Reduce the size of the value in struct perf_pmu_format and avoid holes
so there is no additional space requirement.
For "perf stat -e cycles true" this reduces the number of openat calls
from 648 to 573 (about 12%). The benchmark pmu scan speed is improved
by roughly 5%.
Before:
$ perf bench internals pmu-scan
Computing performance of sysfs PMU event scan for 100 times
Average core PMU scanning took: 1061.100 usec (+- 9.965 usec)
Average PMU scanning took: 4725.300 usec (+- 260.599 usec)
After:
$ perf bench internals pmu-scan
Computing performance of sysfs PMU event scan for 100 times
Average core PMU scanning took: 989.170 usec (+- 6.873 usec)
Average PMU scanning took: 4520.960 usec (+- 251.272 usec)
Committer testing:
On a AMD Ryzen 5950x:
Before:
$ perf bench internals pmu-scan -i1000
# Running 'internals/pmu-scan' benchmark:
Computing performance of sysfs PMU event scan for 1000 times
Average core PMU scanning took: 563.466 usec (+- 1.008 usec)
Average PMU scanning took: 1619.174 usec (+- 23.627 usec)
$ perf stat -r5 perf bench internals pmu-scan -i1000
# Running 'internals/pmu-scan' benchmark:
Computing performance of sysfs PMU event scan for 1000 times
Average core PMU scanning took: 583.401 usec (+- 2.098 usec)
Average PMU scanning took: 1677.352 usec (+- 24.636 usec)
# Running 'internals/pmu-scan' benchmark:
Computing performance of sysfs PMU event scan for 1000 times
Average core PMU scanning took: 553.254 usec (+- 0.825 usec)
Average PMU scanning took: 1635.655 usec (+- 24.312 usec)
# Running 'internals/pmu-scan' benchmark:
Computing performance of sysfs PMU event scan for 1000 times
Average core PMU scanning took: 557.733 usec (+- 0.980 usec)
Average PMU scanning took: 1600.659 usec (+- 23.344 usec)
# Running 'internals/pmu-scan' benchmark:
Computing performance of sysfs PMU event scan for 1000 times
Average core PMU scanning took: 554.906 usec (+- 0.774 usec)
Average PMU scanning took: 1595.338 usec (+- 23.288 usec)
# Running 'internals/pmu-scan' benchmark:
Computing performance of sysfs PMU event scan for 1000 times
Average core PMU scanning took: 551.798 usec (+- 0.967 usec)
Average PMU scanning took: 1623.213 usec (+- 23.998 usec)
Performance counter stats for 'perf bench internals pmu-scan -i1000' (5 runs):
3276.82 msec task-clock:u # 0.990 CPUs utilized ( +- 0.82% )
0 context-switches:u # 0.000 /sec
0 cpu-migrations:u # 0.000 /sec
1008 page-faults:u # 307.615 /sec ( +- 0.04% )
12049614778 cycles:u # 3.677 GHz ( +- 0.07% ) (83.34%)
117507478 stalled-cycles-frontend:u # 0.98% frontend cycles idle ( +- 0.33% ) (83.32%)
27106761 stalled-cycles-backend:u # 0.22% backend cycles idle ( +- 9.55% ) (83.36%)
33294953848 instructions:u # 2.76 insn per cycle
# 0.00 stalled cycles per insn ( +- 0.03% ) (83.31%)
6849825049 branches:u # 2.090 G/sec ( +- 0.03% ) (83.37%)
71533903 branch-misses:u # 1.04% of all branches ( +- 0.20% ) (83.30%)
3.3088 +- 0.0302 seconds time elapsed ( +- 0.91% )
$
After:
$ perf stat -r5 perf bench internals pmu-scan -i1000
# Running 'internals/pmu-scan' benchmark:
Computing performance of sysfs PMU event scan for 1000 times
Average core PMU scanning took: 550.702 usec (+- 0.958 usec)
Average PMU scanning took: 1566.577 usec (+- 22.747 usec)
# Running 'internals/pmu-scan' benchmark:
Computing performance of sysfs PMU event scan for 1000 times
Average core PMU scanning took: 548.315 usec (+- 0.555 usec)
Average PMU scanning took: 1565.499 usec (+- 22.760 usec)
# Running 'internals/pmu-scan' benchmark:
Computing performance of sysfs PMU event scan for 1000 times
Average core PMU scanning took: 548.073 usec (+- 0.555 usec)
Average PMU scanning took: 1586.097 usec (+- 23.299 usec)
# Running 'internals/pmu-scan' benchmark:
Computing performance of sysfs PMU event scan for 1000 times
Average core PMU scanning took: 561.184 usec (+- 2.709 usec)
Average PMU scanning took: 1567.153 usec (+- 22.548 usec)
# Running 'internals/pmu-scan' benchmark:
Computing performance of sysfs PMU event scan for 1000 times
Average core PMU scanning took: 546.987 usec (+- 0.553 usec)
Average PMU scanning took: 1562.814 usec (+- 22.729 usec)
Performance counter stats for 'perf bench internals pmu-scan -i1000' (5 runs):
3170.86 msec task-clock:u # 0.992 CPUs utilized ( +- 0.22% )
0 context-switches:u # 0.000 /sec
0 cpu-migrations:u # 0.000 /sec
1010 page-faults:u # 318.526 /sec ( +- 0.04% )
11890047674 cycles:u # 3.750 GHz ( +- 0.14% ) (83.27%)
119090499 stalled-cycles-frontend:u # 1.00% frontend cycles idle ( +- 0.46% ) (83.40%)
32502449 stalled-cycles-backend:u # 0.27% backend cycles idle ( +- 8.32% ) (83.30%)
33119141261 instructions:u # 2.79 insn per cycle
# 0.00 stalled cycles per insn ( +- 0.01% ) (83.37%)
6812816561 branches:u # 2.149 G/sec ( +- 0.01% ) (83.29%)
70157855 branch-misses:u # 1.03% of all branches ( +- 0.28% ) (83.38%)
3.19710 +- 0.00826 seconds time elapsed ( +- 0.26% )
$
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Gaosheng Cui <cuigaosheng1@huawei.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jing Zhang <renyu.zj@linux.alibaba.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230824041330.266337-2-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 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.