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perf: fix breaking error for creating over perf ring from a loaded pr…#78

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perf: fix breaking error for creating over perf ring from a loaded pr…#78
iAklis wants to merge 1 commit intocilium:masterfrom
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@iAklis iAklis commented Mar 10, 2020

Keep same behavior with libbpf.

The ABI max_entries of in BPF_MAP_TYPE_PERF_EVENT_ARRAY elf is more like a guidance than an exact value.

I'm glad someone reviewed the code for me.

@lmb
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lmb commented Mar 10, 2020

Thank your for the pull request! I'd prefer the approach I mentioned in: #58 (review)

Change the perf ring code in perf to try and create a ring for each slot in the PerfEventArray, and ignore errors due to offline CPUs.

That way the fix for your issue also partially fixes the issue with hotplugged CPUs.

According to man 2 perf_event_open, the syscall fails with EINVAL if the CPU doesn't exist. Problem: there are a bunch of other reasons why that is returned. Maybe we can ignore EINVAL errors, and then at the end check that we created at least a single event ring.

Are you up for that? If not, I'll try and get to this sometime in the next days.

@iAklis iAklis mentioned this pull request Mar 14, 2020
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@lmb lmb mentioned this pull request Mar 17, 2020
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@lmb lmb closed this Mar 19, 2020
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@iAklis @lmb