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Message-Id: <20240603091805.858-1-pugaowei@oppo.com>
Date: Mon, 3 Jun 2024 17:18:05 +0800
From: "Gaowei.Pu" <pugaowei@...o.com>
To: mingo@...hat.com,
peterz@...radead.org,
juri.lelli@...hat.com,
vincent.guittot@...aro.org,
dietmar.eggemann@....com,
rostedt@...dmis.org,
bsegall@...gle.com,
mgorman@...e.de,
bristot@...hat.com,
vschneid@...hat.com
Cc: linux-kernel@...r.kernel.org,
pugaowei <pugaowei@...o.com>
Subject: [PATCH_V2] sched/fair: updates weight of cfs_rq before update_cfs_group() in enqueue_entity()
From: pugaowei <pugaowei@...o.com>
we should update the weight of cfs_rq before update_cfs_group().
Ensure that we can get accurate shares of the cfs_rq when its
weights changes. we can find this work was done correctly in
dequeue_entity(). so fix it.
patch_V1 :
https://lore.kernel.org/lkml/20240531030833.3375-1-pugaowei@oppo.com/T/#u
trigger a warnning below because of the changing order of
account_entity_enqueue().
[ 0.400603][ T0] ? __warn (kernel/panic.c:693)
[ 0.400603][ T0] ? place_entity (kernel/sched/fair.c:5256 (discriminator 1))
[ 0.400603][ T0] ? report_bug (lib/bug.c:180 lib/bug.c:219)
[ 0.400603][ T0] ? handle_bug (arch/x86/kernel/traps.c:239)
[ 0.400603][ T0] ? exc_invalid_op (arch/x86/kernel/traps.c:260 (discriminator 1))
[ 0.400603][ T0] ? asm_exc_invalid_op (arch/x86/include/asm/idtentry.h:621)
[ 0.400603][ T0] ? place_entity (kernel/sched/fair.c:5256 (discriminator 1))
[ 0.400603][ T0] ? place_entity (kernel/sched/fair.c:5182)
[ 0.400603][ T0] enqueue_entity (kernel/sched/fair.c:5328)
[ 0.400603][ T0] enqueue_task_fair (kernel/sched/fair.c:6785)
V2 fix the warnning and keep the lag without inflating it when it is
the first sched_entity queued on the cfs_rq.
Signed-off-by: pugaowei <pugaowei@...o.com>
---
kernel/sched/fair.c | 24 ++++++++++++++++--------
1 file changed, 16 insertions(+), 8 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8a5b1ae0aa55..2fb1fbcfdda3 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5190,12 +5190,12 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
*
* EEVDF: placement strategy #1 / #2
*/
- if (sched_feat(PLACE_LAG) && cfs_rq->nr_running) {
+ if (sched_feat(PLACE_LAG)) {
struct sched_entity *curr = cfs_rq->curr;
- unsigned long load;
+ unsigned long load, se_load;
lag = se->vlag;
-
+ se_load = scale_load_down(se->load.weight);
/*
* If we want to place a task and preserve lag, we have to
* consider the effect of the new entity on the weighted
@@ -5252,9 +5252,13 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
if (curr && curr->on_rq)
load += scale_load_down(curr->load.weight);
- lag *= load + scale_load_down(se->load.weight);
- if (WARN_ON_ONCE(!load))
- load = 1;
+ lag *= load + se_load;
+ /*
+ * we just need to keep the lag whithout inflating it when the se is
+ * the first sched_entity queued on cfs_rq.
+ */
+ if (!load)
+ load = se_load;
lag = div_s64(lag, load);
}
@@ -5304,6 +5308,12 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
*/
update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
se_update_runnable(se);
+
+ /*
+ * we should update the weight of cfs_rq before update_cfs_group.
+ * Ensure we can get accurate shares of the cfs_rq when its weights changes.
+ */
+ account_entity_enqueue(cfs_rq, se);
/*
* XXX update_load_avg() above will have attached us to the pelt sum;
* but update_cfs_group() here will re-adjust the weight and have to
@@ -5318,8 +5328,6 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
if (!curr)
place_entity(cfs_rq, se, flags);
- account_entity_enqueue(cfs_rq, se);
-
/* Entity has migrated, no longer consider this task hot */
if (flags & ENQUEUE_MIGRATED)
se->exec_start = 0;
--
2.17.1
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