** Changed in: linux-aws (Ubuntu Noble)
Status: In Progress => Fix Committed
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https://bugs.launchpad.net/bugs/2106004
Title:
Backport Perf patchset to address Linux kernels performance regression
Status in linux-aws package in Ubuntu:
Fix Released
Status in linux-aws source package in Noble:
Fix Committed
Bug description:
SRU Justification:
[Impact]
A significant regression (between 0.5x and 0.2x) in benchmark results
has been noticed on Stream when profiled with APerf. On further
investigation it has been identified that the regression is coming
from the Linux Perf subsystem which is used by APerf to collect PMU
metrics and Flamegraph profiling data.
The regression first occured between v6.1 and v6.2 of the upstream
linux kernel.
[Fix]
It has been identified this patchset:
https://lore.kernel.org/lkml/20240111204348.669673-1-namhy...@kernel.org/
, which was merged in v6.10 to fix the performance regression.
These changes correspond to upstream commits:
f38628b06c36
0259bf63f71e
[Test Plan]
AWS tested
[Where problems could occur]
The changes are fairly narrow in scope, and changes how the PMU checks
frequencies and throttles. As this is fixing a regression if a system
is relying on the behaviour present after the regression was
introduced, and before it is fixed, it may have strange side effects.
The other area that this may have problems is if the stable branches bring in
changes to the PMU throttling code that does not have this fix corrected,
strange behaviour may result, or merge conflicts may occur.
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[Other Info]
SF #00407096
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