6.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Chen Yu <yu.c.chen@xxxxxxxxx>
[ Upstream commit 84d265281d6cea65353fc24146280e0d86ac50cb ]
commit 97450eb90965 ("sched/pelt: Remove shift of thermal clock")
removed the decay_shift for hw_pressure. This commit uses the
sched_clock_task() in sched_tick() while it replaces the
sched_clock_task() with rq_clock_pelt() in __update_blocked_others().
This could bring inconsistence. One possible scenario I can think of
is in ___update_load_sum():
u64 delta = now - sa->last_update_time
'now' could be calculated by rq_clock_pelt() from
__update_blocked_others(), and last_update_time was calculated by
rq_clock_task() previously from sched_tick(). Usually the former
chases after the latter, it cause a very large 'delta' and brings
unexpected behavior.
Fixes: 97450eb90965 ("sched/pelt: Remove shift of thermal clock")
Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Hongyan Xia <hongyan.xia2@xxxxxxx>
Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20240827112607.181206-1-yu.c.chen@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
kernel/sched/fair.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3c59f2b34a779..5e4162d02afc1 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9365,9 +9365,10 @@ static bool __update_blocked_others(struct rq *rq, bool *done)
hw_pressure = arch_scale_hw_pressure(cpu_of(rq));
+ /* hw_pressure doesn't care about invariance */
decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
- update_hw_load_avg(now, rq, hw_pressure) |
+ update_hw_load_avg(rq_clock_task(rq), rq, hw_pressure) |
update_irq_load_avg(rq, 0);
if (others_have_blocked(rq))
--
2.43.0
