sched_ext/scx_flatcg: expire cached hweights on weight changes

Browse source

fcg_cgroup_set_weight() updates cgc->weight and the parent's
child_weight_sum but doesn't bump hweight_gen, so the hweights cached by
cgrp_refresh_hweight() stay stale until some task activation bumps the
generation. For cgroups whose tasks never go through a 0->n runnable
transition (e.g. persistently busy ones), a cpu.weight change never
propagates to scheduling at all.

Bump hweight_gen on weight changes so the next refresh recomputes with
the new weight.

Verified on a flatcg VM: a live cpu.weight 100->800 change on a busy
cgroup leaves HWT update at 0 and the distribution unchanged; with it,
hweight_gen increments and the refresh recomputes.

Signed-off-by: Tao Cui <cuitao@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>

...

This commit is contained in:

Tao Cui 2026-08-14 22:41:16 +08:00 • committed by Tejun Heo

parent 03506edca6

commit 94c20e1fb3

1 changed files with 3 additions and 0 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

3

tools/sched_ext/scx_flatcg.bpf.c

View file