sched_ext: scx_qmap - Idle-check pinned tasks before direct dispatch

Browse source

pick_direct_dispatch_cid() sent a pinned task straight to its only cpu
without an idle check. An insert onto a time-shared cid is forced IMMED,
which may not wait on a busy cpu - the kernel bounces the task back to
ops.enqueue(), the shortcut re-inserts it, and the loop runs into the
reenqueue repeat limit.

Run pinned tasks through the same idle test as everyone else and queue them
when the cpu is busy. always_enq_immed forces IMMED on every local insert
and already skipped the shortcut for the same reason. The check was the last
reader of the always_enq_immed rodata mirror, so drop the variable. The -I
option still sets SCX_OPS_ALWAYS_ENQ_IMMED.

v2: Drop the now-unread always_enq_immed rodata mirror. (sashiko AI)

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

...

This commit is contained in:

Tejun Heo 2026-08-03 11:01:55 -10:00

parent 1f15b9a949

commit 6206980186

2 changed files with 0 additions and 5 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

4

tools/sched_ext/scx_qmap.bpf.c

View file

1

tools/sched_ext/scx_qmap.c

View file