Refactor select_cpu + enqueue for proper synchronization and handle of !wakeup #438
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Missed this in some previous commits. Just running clang-format. Signed-off-by: Dan Schatzberg <[email protected]>
If we're not on the wakeup path, we may see enqueue() invoked without select_cpu() which will require an idle cpu lookup. In order to fix this, we refactor the idle_cpu lookup in select_cpu so it can be invoked from enqueue(). Signed-off-by: Dan Schatzberg <[email protected]>
scx_mitosis relied on the implicit assumption that after a sched tick, all outstanding scheduling events had completed but this might not actually be correct. This feels like a natural use-case for RCU, but there is no way to directly make use of RCU in BPF. Instead, this commit implements an RCU-like synchronization mechanism. Signed-off-by: Dan Schatzberg <[email protected]>
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I think it's lacking necessary memory barriers even on x86 as rmb isn't implied but this looks like a great starting point. |
htejun
approved these changes
Jul 18, 2024
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Is this PR still in progress? |
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I was planning on repurposing it just for the RCU bits since there's some
context. Hopefully next week I'll update it
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