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linux_perf_event fails on aarch64 since exclude_idle is set #2298

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bhalevy opened this issue Jun 18, 2024 · 0 comments · May be fixed by #2295
Open

linux_perf_event fails on aarch64 since exclude_idle is set #2298

bhalevy opened this issue Jun 18, 2024 · 0 comments · May be fixed by #2295

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@bhalevy
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bhalevy commented Jun 18, 2024

As seen in scylladb/scylladb#19227 (comment)
exclude_idle is not supported on ARM platforms causing the perf_event_open system call to fail.

The documentation in https://man7.org/linux/man-pages/man2/perf_event_open.2.html says:

       EPERM  Returned on many (but not all) architectures when an
              unsupported exclude_hv, exclude_idle, exclude_user, or
              exclude_kernel setting is specified.

FWIW, although this applies to several bitfields in the linux perf_event_attr, we've only seen an issue now with exclude_idle on arm.
bhalevy added a commit to bhalevy/seastar that referenced this issue Jun 18, 2024
@bhalevy
linux_perf_event: exclude_idle only on x86_64
08041ad 
Commit 93f19d3
added `exclude_idle = 1` to `linux_perf_event`.
However, as reported in
scylladb/scylladb#19227 (comment),
`exclude_idle` is not supported on ARM platforms.

This change sets `exclude_idle` only on known-to-work architectures
(presently, it's only x86_64), assuming it is initialized to 0 as all
other unset bitfields in `perf_event_attr`.

Fixes scylladb#2298

Signed-off-by: Benny Halevy <[email protected]>
@bhalevy bhalevy linked a pull request Jun 18, 2024 that will close this issue
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bhalevy added a commit to bhalevy/seastar that referenced this issue Jul 1, 2024
@bhalevy
linux_perf_event: exclude_idle only on x86_64
041523e 
Commit 93f19d3
added `exclude_idle = 1` to `linux_perf_event`.
However, as reported in
scylladb/scylladb#19227 (comment),
`exclude_idle` is not supported on ARM platforms.

This change sets `exclude_idle` only on known-to-work architectures
(presently, it's only x86_64), assuming it is initialized to 0 as all
other unset bitfields in `perf_event_attr`.

Fixes scylladb#2298

Signed-off-by: Benny Halevy <[email protected]>
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linux_perf_event: exclude_idle only on x86_64 bhalevy/seastar
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