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sched_ext: Skip per-CPU tasks in scx_bpf_reenqueue_local()

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scx_bpf_reenqueue_local() can be invoked from ops.cpu_release() to give
tasks that are queued to the local DSQ a chance to migrate to other
CPUs, when a CPU is taken by a higher scheduling class.

However, there is no point re-enqueuing tasks that can only run on that
particular CPU, as they would simply be re-added to the same local DSQ
without any benefit.

Therefore, skip per-CPU tasks in scx_bpf_reenqueue_local().

Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Andrea Righi 2025-03-13 18:03:21 +01:00 committed by Tejun Heo
parent 71d078803c
commit 97e13ecb02
1 changed files with 5 additions and 1 deletions
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6
kernel/sched/ext.c
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@ -6621,8 +6621,12 @@ __bpf_kfunc u32 scx_bpf_reenqueue_local(void)
* CPUs disagree, they use %ENQUEUE_RESTORE which is bypassed to
* the current local DSQ for running tasks and thus are not
* visible to the BPF scheduler.
*
* Also skip re-enqueueing tasks that can only run on this
* CPU, as they would just be re-added to the same local
* DSQ without any benefit.
*/
if (p->migration_pending)
if (p->migration_pending || is_migration_disabled(p) || p->nr_cpus_allowed == 1)
continue;
dispatch_dequeue(rq, p);