[24.04_linux-nvidia-6.17] Backport perf tool_pmu: Use old_count when computing count values for time events#471
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When running in interval mode every third count of a time event isn't
showing properly:
```
$ perf stat -e duration_time -a -I 1000
1.001082862 1,002,290,425 duration_time
2.004264262 1,003,183,516 duration_time
3.007381401 <not counted> duration_time
4.011160141 1,003,705,631 duration_time
5.014515385 1,003,290,110 duration_time
6.018539680 <not counted> duration_time
7.022065321 1,003,591,720 duration_time
```
The regression came in with a different fix, found through bisection,
commit 68cb156 ("perf tool_pmu: Fix aggregation on
duration_time"). The issue is caused by the enabled and running time
of the event matching the old_count's and creating a delta of 0, which
is indicative of an error.
Fixes: 68cb156 ("perf tool_pmu: Fix aggregation on duration_time")
Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
(backported from commit bdf96c4)
[mochs: Minor context adjustment due to absent definitions]
Signed-off-by: Matthew R. Ochs <mochs@nvidia.com>
Collaborator
BaseOS Kernel ReviewSummaryOnly a low-severity issue found: in tools/perf/util/tool_pmu.c, the time conversion uses a floating-point literal (1e9), which can lose precision for very large __u64 deltas, though practical impact on perf time stats is negligible. Findings: Critical: 0, High: 0, Medium: 0, Low: 1 Latest watcher review: open review Kernel deb build: failed (failure log, build artifacts) Head: This comment is maintained by nv-pr-bot. It is updated when the GitHub watcher publishes a newer review. |
Contributor
PR Validation ReportPatchscan ✅ No Missing FixesAll cherry-picked commits checked — no missing upstream fixes found. PR Lint ❌ Errors foundDetailsChecking 1 commits...
Cherry-pick digest:
E: b30d2bbf616f ("perf tool_pmu: Use old_count when comput"): patch-ID mismatch with upstream bdf96c4ecd69
┌──────────────┬──────────────────────────────────────────────────────────────────┬────────────┬─────────┬───────────────────────────┐
│ Local │ Referenced upstream / Patch subject │ Patch-ID │ Subject │ SoB chain │
├──────────────┼──────────────────────────────────────────────────────────────────┼────────────┼─────────┼───────────────────────────┤
│ b30d2bbf616f │ bdf96c4ecd69 perf tool_pmu: Use old_count when computing count v │ MISMATCH │ match │ preserved + mochs added │
└──────────────┴──────────────────────────────────────────────────────────────────┴────────────┴─────────┴───────────────────────────┘
Lint: all checks passed.
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Acked-by: Carol L Soto <csoto@nvidia.com>
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Acked-by: Nirmoy Das <nirmoyd@nvidia.com>
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Merged, closing PR. |
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This upstream patch from v6.19 resolves an issue (injected with a v6.16 commit) when running the perf command to measure duration time.
When running in interval mode every third count of a time event isn't
showing properly:
Patch: torvalds/linux@bdf96c4
LKML: https://lore.kernel.org/all/20251113180517.44096-4-irogers@google.com/
Backport the patch to linux-nvidia-6.17.
Verified by running the perf command with the fix:
LP: https://bugs.launchpad.net/ubuntu/+source/linux-nvidia-6.17/+bug/2158038