398a8ac2e8
* Build libpfm as a dependency to allow collection of perf counters
This commit builds libpfm using rules_foreign_cc and lets the default
build of the benchmark library support perf counter collection without
needing additional work from users.
Tested with a custom target:
```
bazel run \
--override_repository=com_github_google_benchmark=/home/raghu/benchmark \
-c opt :test-bench -- "--benchmark_perf_counters=INSTRUCTIONS,CYCLES"
Using profile: local
<snip>
----------------------------------------------------------------------
Benchmark Time CPU Iterations UserCounters...
----------------------------------------------------------------------
BM_Test 0.279 ns 0.279 ns 1000000000 CYCLES=1.00888 INSTRUCTIONS=2
```
Signed-off-by: Raghu Raja <raghu@enfabrica.net>
* Adding myself to the CONTRIBUTORS file per CLA guidance
Enfabrica has already signed a corporate CLA.
Signed-off-by: Raghu Raja <raghu@enfabrica.net>
Signed-off-by: Raghu Raja <raghu@enfabrica.net>
1.5 KiB
User-Requested Performance Counters
When running benchmarks, the user may choose to request collection of performance counters. This may be useful in investigation scenarios - narrowing down the cause of a regression; or verifying that the underlying cause of a performance improvement matches expectations.
This feature is available if:
- The benchmark is run on an architecture featuring a Performance Monitoring Unit (PMU),
- The benchmark is compiled with support for collecting counters. Currently, this requires libpfm, which is built as a dependency via Bazel.
The feature does not require modifying benchmark code. Counter collection is handled at the boundaries where timer collection is also handled.
To opt-in:
- If using a Bazel build, add
--define pfm=1to your buid flags - If using CMake:
- Install
libpfm4-dev, e.g.apt-get install libpfm4-dev. - Enable the CMake flag
BENCHMARK_ENABLE_LIBPFMinCMakeLists.txt.
- Install
To use, pass a comma-separated list of counter names through the
--benchmark_perf_counters flag. The names are decoded through libpfm - meaning,
they are platform specific, but some (e.g. CYCLES or INSTRUCTIONS) are
mapped by libpfm to platform-specifics - see libpfm
documentation for more details.
The counter values are reported back through the User Counters mechanism, meaning, they are available in all the formats (e.g. JSON) supported by User Counters.