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| author | xupengbo <xupengbo@oppo.com> | 2025-08-27 05:22:07 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2025-12-06 12:03:13 +0300 |
| commit | ca125231dd29fc0678dd3622e9cdea80a51dffe4 (patch) | |
| tree | c28b6a52ab79956224720cf7827733132c628057 | |
| parent | 22abd832776b1317ae4c3f8a097c8b71bf83fb38 (diff) | |
| download | linux-ca125231dd29fc0678dd3622e9cdea80a51dffe4.tar.xz | |
sched/fair: Fix unfairness caused by stalled tg_load_avg_contrib when the last task migrates out
When a task is migrated out, there is a probability that the tg->load_avg
value will become abnormal. The reason is as follows:
1. Due to the 1ms update period limitation in update_tg_load_avg(), there
is a possibility that the reduced load_avg is not updated to tg->load_avg
when a task migrates out.
2. Even though __update_blocked_fair() traverses the leaf_cfs_rq_list and
calls update_tg_load_avg() for cfs_rqs that are not fully decayed, the key
function cfs_rq_is_decayed() does not check whether
cfs->tg_load_avg_contrib is null. Consequently, in some cases,
__update_blocked_fair() removes cfs_rqs whose avg.load_avg has not been
updated to tg->load_avg.
Add a check of cfs_rq->tg_load_avg_contrib in cfs_rq_is_decayed(),
which fixes the case (2.) mentioned above.
Fixes: 1528c661c24b ("sched/fair: Ratelimit update to tg->load_avg")
Signed-off-by: xupengbo <xupengbo@oppo.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Aaron Lu <ziqianlu@bytedance.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Tested-by: Aaron Lu <ziqianlu@bytedance.com>
Link: https://patch.msgid.link/20250827022208.14487-1-xupengbo@oppo.com
| -rw-r--r-- | kernel/sched/fair.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 769d7b7990df..da46c3164537 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4034,6 +4034,9 @@ static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq) if (child_cfs_rq_on_list(cfs_rq)) return false; + if (cfs_rq->tg_load_avg_contrib) + return false; + return true; } |