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author | 2019-11-12 15:50:43 +0100 | |
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committer | 2019-11-18 14:33:12 +0100 | |
commit | a9723389cc759c891d481de271ac73eeaa123bcb (patch) | |
tree | 302cb8c108b42b991c659ab6fbe8b7d90fa49144 /kernel/sched | |
parent | sched/fair: Fix rework of find_idlest_group() (diff) | |
download | linux-a9723389cc759c891d481de271ac73eeaa123bcb.tar.gz linux-a9723389cc759c891d481de271ac73eeaa123bcb.tar.bz2 linux-a9723389cc759c891d481de271ac73eeaa123bcb.zip |
sched/fair: Add comments for group_type and balancing at SD_NUMA level
Add comments to describe each state of goup_type and to add some details
about the load balance at NUMA level.
[ Valentin Schneider: Updates to the comments. ]
[ mingo: Other updates to the comments. ]
Reported-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Acked-by: Valentin Schneider <valentin.schneider@arm.com>
Cc: Ben Segall <bsegall@google.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/1573570243-1903-1-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r-- | kernel/sched/fair.c | 35 |
1 files changed, 31 insertions, 4 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 2fc08e7d9cd6..1f93d96dd06b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6980,17 +6980,40 @@ static unsigned long __read_mostly max_load_balance_interval = HZ/10; enum fbq_type { regular, remote, all }; /* - * group_type describes the group of CPUs at the moment of the load balance. + * 'group_type' describes the group of CPUs at the moment of load balancing. + * * The enum is ordered by pulling priority, with the group with lowest priority - * first so the groupe_type can be simply compared when selecting the busiest - * group. see update_sd_pick_busiest(). + * first so the group_type can simply be compared when selecting the busiest + * group. See update_sd_pick_busiest(). */ enum group_type { + /* The group has spare capacity that can be used to run more tasks. */ group_has_spare = 0, + /* + * The group is fully used and the tasks don't compete for more CPU + * cycles. Nevertheless, some tasks might wait before running. + */ group_fully_busy, + /* + * SD_ASYM_CPUCAPACITY only: One task doesn't fit with CPU's capacity + * and must be migrated to a more powerful CPU. + */ group_misfit_task, + /* + * SD_ASYM_PACKING only: One local CPU with higher capacity is available, + * and the task should be migrated to it instead of running on the + * current CPU. + */ group_asym_packing, + /* + * The tasks' affinity constraints previously prevented the scheduler + * from balancing the load across the system. + */ group_imbalanced, + /* + * The CPU is overloaded and can't provide expected CPU cycles to all + * tasks. + */ group_overloaded }; @@ -8589,7 +8612,11 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s /* * Try to use spare capacity of local group without overloading it or - * emptying busiest + * emptying busiest. + * XXX Spreading tasks across NUMA nodes is not always the best policy + * and special care should be taken for SD_NUMA domain level before + * spreading the tasks. For now, load_balance() fully relies on + * NUMA_BALANCING and fbq_classify_group/rq to override the decision. */ if (local->group_type == group_has_spare) { if (busiest->group_type > group_fully_busy) { |