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Add note on how to use perf record if PMU counters are not available.

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Bug: 313526654
Change-Id: Iab8b2915c0627f5830344cb8145810f7898b5409
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5337346
Reviewed-by: David Benjamin <davidben@chromium.org>
Auto-Submit: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1267454}
This commit is contained in:
Daniel Cheng
2024-03-01 18:36:08 +00:00
committed by Chromium LUCI CQ
parent 26cfb48fda
commit 3e1b99498f
1 changed files with 4 additions and 0 deletions

4
docs/linux/profiling.md

@ -35,6 +35,10 @@ perf record -f -g -p 1234
perf record -f -g -a # captures the whole system
```
> ⚠️ Note: on virtualized systems, e.g. cloudtops, the PMU counters may not
be available or may be broken. Use `-e cpu-clock` as a workaround.
Googlers, see [b/313526654](https://b.corp.google.com/issues/313526654).
Some versions of the perf command can be confused by process renames. Affected
versions will be unable to resolve Chromium's symbols if it was started through
perf, as in the first example above. It should work correctly if you attach to