Messages in this thread Patch in this message | | | From | Valentin Schneider <> | Subject | [PATCH] sched/fair: Don't increase sd->balance_interval on newidle balance | Date | Tue, 25 Sep 2018 18:35:22 +0100 |
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When load_balance() fails to move some load because of task affinity, we end up increasing sd->balance_interval to delay the next periodic balance in the hopes that next time we look, that annoying pinned task(s) will be gone.
However, idle_balance() pays no attention to sd->balance_interval, yet it will still lead to an increase in balance_interval in case of pinned tasks.
If we're going through several newidle balances (e.g. we have a periodic task), this can lead to a huge increase of the balance_interval in a very small amount of time.
To prevent that, don't increase the balance interval when going through a newidle balance.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> --- kernel/sched/fair.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 6bd142d..620910d 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8782,13 +8782,22 @@ static int load_balance(int this_cpu, struct rq *this_rq, sd->nr_balance_failed = 0; out_one_pinned: + ld_moved = 0; + + /* + * idle_balance() disregards balance intervals, so we could repeatedly + * reach this code, which would lead to balance_interval skyrocketting + * in a short amount of time. Skip the balance_interval increase logic + * to avoid that. + */ + if (env.idle == CPU_NEWLY_IDLE) + goto out; + /* tune up the balancing interval */ - if (((env.flags & LBF_ALL_PINNED) && - sd->balance_interval < MAX_PINNED_INTERVAL) || - (sd->balance_interval < sd->max_interval)) + if ((env.flags & LBF_ALL_PINNED && + sd->balance_interval < MAX_PINNED_INTERVAL) || + (sd->balance_interval < sd->max_interval)) sd->balance_interval *= 2; - - ld_moved = 0; out: return ld_moved; } -- 2.7.4
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