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scx_flash: Clarify conditions for reusing prev_cpu on sync wakeup #2288

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Merged
arighi merged 1 commit into from
Jun 29, 2025
Merged

scx_flash: Clarify conditions for reusing prev_cpu on sync wakeup #2288

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11 changes: 8 additions & 3 deletions scheds/rust/scx_flash/src/bpf/main.bpf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -730,9 +730,14 @@ static s32 pick_idle_cpu(struct task_struct *p, s32 prev_cpu, u64 wake_flags, bo

/*
* If waker and wakee are on the same LLC and @prev_cpu is
* idle keep using it, since there is no guarantee that the
* cache hot data from the waker's CPU is more important
* than cache hot data in the wakee's CPU.
* idle, keep using it, since there is no guarantee that
* the cache hot data from the waker's CPU is more
* important than cache hot data in the wakee's CPU.
*
* @prev_cpu is considered idle under the following
* conditions:
* - if SMT is enabled, check if it's a full-idle core;
* - if SMT is disabled, check if the CPU is idle.
*/
if (share_llc &&
(!smt_enabled || bpf_cpumask_test_cpu(prev_cpu, idle_smtmask)) &&
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