The following commit has been merged into the sched/core branch of tip: Commit-ID: 8a41dfcda7a32ed4435c00d98a9dc7156b08b671 Gitweb: https://git.kernel.org/tip/8a41dfcda7a32ed4435c00d98a9dc7156b08b671 Author: Vincent Guittot <vincent.guit...@linaro.org> AuthorDate: Thu, 07 Jan 2021 11:33:24 +01:00 Committer: Peter Zijlstra <pet...@infradead.org> CommitterDate: Thu, 14 Jan 2021 11:20:11 +01:00
sched/fair: Don't set LBF_ALL_PINNED unnecessarily Setting LBF_ALL_PINNED during active load balance is only valid when there is only 1 running task on the rq otherwise this ends up increasing the balance interval whereas other tasks could migrate after the next interval once they become cache-cold as an example. LBF_ALL_PINNED flag is now always set it by default. It is then cleared when we find one task that can be pulled when calling detach_tasks() or during active migration. Signed-off-by: Vincent Guittot <vincent.guit...@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Reviewed-by: Valentin Schneider <valentin.schnei...@arm.com> Acked-by: Mel Gorman <mgor...@suse.de> Link: https://lkml.kernel.org/r/20210107103325.30851-3-vincent.guit...@linaro.org --- kernel/sched/fair.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 13de7ae..48f99c8 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9639,6 +9639,8 @@ redo: env.src_rq = busiest; ld_moved = 0; + /* Clear this flag as soon as we find a pullable task */ + env.flags |= LBF_ALL_PINNED; if (busiest->nr_running > 1) { /* * Attempt to move tasks. If find_busiest_group has found @@ -9646,7 +9648,6 @@ redo: * still unbalanced. ld_moved simply stays zero, so it is * correctly treated as an imbalance. */ - env.flags |= LBF_ALL_PINNED; env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running); more_balance: @@ -9772,10 +9773,12 @@ more_balance: if (!cpumask_test_cpu(this_cpu, busiest->curr->cpus_ptr)) { raw_spin_unlock_irqrestore(&busiest->lock, flags); - env.flags |= LBF_ALL_PINNED; goto out_one_pinned; } + /* Record that we found at least one task that could run on this_cpu */ + env.flags &= ~LBF_ALL_PINNED; + /* * ->active_balance synchronizes accesses to * ->active_balance_work. Once set, it's cleared
