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sched_ext: keep running prev when prev->scx.slice != 0

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When %SCX_OPS_ENQ_LAST is set and prev->scx.slice != 0,
@prev will be dispacthed into the local DSQ in put_prev_task_scx().
However, pick_task_scx() is executed before put_prev_task_scx(),
so it will not pick @prev.
Set %SCX_RQ_BAL_KEEP in balance_one() to ensure that pick_task_scx()
can pick @prev.

Signed-off-by: Henry Huang <henry.hj@antgroup.com>
Acked-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Henry Huang 2025-01-08 16:47:10 +08:00 committed by Tejun Heo
parent ce2b93fc1d
commit 30dd3b13f9
1 changed files with 7 additions and 4 deletions
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11
kernel/sched/ext.c
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@ -2747,6 +2747,7 @@ static int balance_one(struct rq *rq, struct task_struct *prev)
{
struct scx_dsp_ctx *dspc = this_cpu_ptr(scx_dsp_ctx);
bool prev_on_scx = prev->sched_class == &ext_sched_class;
bool prev_on_rq = prev->scx.flags & SCX_TASK_QUEUED;
int nr_loops = SCX_DSP_MAX_LOOPS;
lockdep_assert_rq_held(rq);
@ -2779,8 +2780,7 @@ static int balance_one(struct rq *rq, struct task_struct *prev)
* See scx_ops_disable_workfn() for the explanation on the
* bypassing test.
*/
if ((prev->scx.flags & SCX_TASK_QUEUED) &&
prev->scx.slice && !scx_rq_bypassing(rq)) {
if (prev_on_rq && prev->scx.slice && !scx_rq_bypassing(rq)) {
rq->scx.flags |= SCX_RQ_BAL_KEEP;
goto has_tasks;
}
@ -2813,6 +2813,10 @@ static int balance_one(struct rq *rq, struct task_struct *prev)
flush_dispatch_buf(rq);
if (prev_on_rq && prev->scx.slice) {
rq->scx.flags |= SCX_RQ_BAL_KEEP;
goto has_tasks;
}
if (rq->scx.local_dsq.nr)
goto has_tasks;
if (consume_global_dsq(rq))
@ -2838,8 +2842,7 @@ no_tasks:
* Didn't find another task to run. Keep running @prev unless
* %SCX_OPS_ENQ_LAST is in effect.
*/
if ((prev->scx.flags & SCX_TASK_QUEUED) &&
(!static_branch_unlikely(&scx_ops_enq_last) ||
if (prev_on_rq && (!static_branch_unlikely(&scx_ops_enq_last) ||
scx_rq_bypassing(rq))) {
rq->scx.flags |= SCX_RQ_BAL_KEEP;
goto has_tasks;