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author | Vincent Guittot <vincent.guittot@linaro.org> | 2019-10-18 15:26:28 +0200 |
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committer | Ingo Molnar <mingo@kernel.org> | 2019-10-21 09:40:53 +0200 |
commit | 490ba971d8b498ba3a47999ab94c6a0d1830ad41 (patch) | |
tree | d738c6ac9b8d76ddfd0fd98bbd2a953ec4721c44 /kernel/sched/fair.c | |
parent | 9ae7ab20b4835dbea0e5fc6a5c70171dc354a72e (diff) | |
download | linux-stable-490ba971d8b498ba3a47999ab94c6a0d1830ad41.tar.gz linux-stable-490ba971d8b498ba3a47999ab94c6a0d1830ad41.tar.bz2 linux-stable-490ba971d8b498ba3a47999ab94c6a0d1830ad41.zip |
sched/fair: Clean up asym packing
Clean up asym packing to follow the default load balance behavior:
- classify the group by creating a group_asym_packing field.
- calculate the imbalance in calculate_imbalance() instead of bypassing it.
We don't need to test twice same conditions anymore to detect asym packing
and we consolidate the calculation of imbalance in calculate_imbalance().
There is no functional changes.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Acked-by: Rik van Riel <riel@surriel.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: Mel Gorman <mgorman@suse.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Morten.Rasmussen@arm.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: hdanton@sina.com
Cc: parth@linux.ibm.com
Cc: pauld@redhat.com
Cc: quentin.perret@arm.com
Cc: srikar@linux.vnet.ibm.com
Cc: valentin.schneider@arm.com
Link: https://lkml.kernel.org/r/1571405198-27570-2-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched/fair.c')
-rw-r--r-- | kernel/sched/fair.c | 63 |
1 files changed, 16 insertions, 47 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 682a754ea3e1..5ce0f71042ad 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7665,6 +7665,7 @@ struct sg_lb_stats { unsigned int group_weight; enum group_type group_type; int group_no_capacity; + unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */ unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */ #ifdef CONFIG_NUMA_BALANCING unsigned int nr_numa_running; @@ -8119,9 +8120,17 @@ asym_packing: * ASYM_PACKING needs to move all the work to the highest * prority CPUs in the group, therefore mark all groups * of lower priority than ourself as busy. + * + * This is primarily intended to used at the sibling level. Some + * cores like POWER7 prefer to use lower numbered SMT threads. In the + * case of POWER7, it can move to lower SMT modes only when higher + * threads are idle. When in lower SMT modes, the threads will + * perform better since they share less core resources. Hence when we + * have idle threads, we want them to be the higher ones. */ if (sgs->sum_nr_running && sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) { + sgs->group_asym_packing = 1; if (!sds->busiest) return true; @@ -8263,51 +8272,6 @@ next_group: } /** - * check_asym_packing - Check to see if the group is packed into the - * sched domain. - * - * This is primarily intended to used at the sibling level. Some - * cores like POWER7 prefer to use lower numbered SMT threads. In the - * case of POWER7, it can move to lower SMT modes only when higher - * threads are idle. When in lower SMT modes, the threads will - * perform better since they share less core resources. Hence when we - * have idle threads, we want them to be the higher ones. - * - * This packing function is run on idle threads. It checks to see if - * the busiest CPU in this domain (core in the P7 case) has a higher - * CPU number than the packing function is being run on. Here we are - * assuming lower CPU number will be equivalent to lower a SMT thread - * number. - * - * Return: 1 when packing is required and a task should be moved to - * this CPU. The amount of the imbalance is returned in env->imbalance. - * - * @env: The load balancing environment. - * @sds: Statistics of the sched_domain which is to be packed - */ -static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds) -{ - int busiest_cpu; - - if (!(env->sd->flags & SD_ASYM_PACKING)) - return 0; - - if (env->idle == CPU_NOT_IDLE) - return 0; - - if (!sds->busiest) - return 0; - - busiest_cpu = sds->busiest->asym_prefer_cpu; - if (sched_asym_prefer(busiest_cpu, env->dst_cpu)) - return 0; - - env->imbalance = sds->busiest_stat.group_load; - - return 1; -} - -/** * fix_small_imbalance - Calculate the minor imbalance that exists * amongst the groups of a sched_domain, during * load balancing. @@ -8391,6 +8355,11 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s local = &sds->local_stat; busiest = &sds->busiest_stat; + if (busiest->group_asym_packing) { + env->imbalance = busiest->group_load; + return; + } + if (busiest->group_type == group_imbalanced) { /* * In the group_imb case we cannot rely on group-wide averages @@ -8495,8 +8464,8 @@ static struct sched_group *find_busiest_group(struct lb_env *env) busiest = &sds.busiest_stat; /* ASYM feature bypasses nice load balance check */ - if (check_asym_packing(env, &sds)) - return sds.busiest; + if (busiest->group_asym_packing) + goto force_balance; /* There is no busy sibling group to pull tasks from */ if (!sds.busiest || busiest->sum_nr_running == 0) |