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sched/fair: Fix unnecessary increase of balance interval
In case of active balancing, we increase the balance interval to cover pinned tasks cases not covered by all_pinned logic. Neverthless, the active migration triggered by asym packing should be treated as the normal unbalanced case and reset the interval to default value, otherwise active migration for asym_packing can be easily delayed for hundreds of ms because of this pinned task detection mechanism. The same happens to other conditions tested in need_active_balance() like misfit task and when the capacity of src_cpu is reduced compared to dst_cpu (see comments in need_active_balance() for details). Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: valentin.schneider@arm.com Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -8826,22 +8826,26 @@ static struct rq *find_busiest_queue(struct lb_env *env,
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*/
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#define MAX_PINNED_INTERVAL 512
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static int need_active_balance(struct lb_env *env)
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static inline bool
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asym_active_balance(struct lb_env *env)
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{
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struct sched_domain *sd = env->sd;
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if (env->idle != CPU_NOT_IDLE) {
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/*
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* ASYM_PACKING needs to force migrate tasks from busy but
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* lower priority CPUs in order to pack all tasks in the
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* highest priority CPUs.
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*/
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if ((sd->flags & SD_ASYM_PACKING) &&
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sched_asym_prefer(env->dst_cpu, env->src_cpu))
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return 1;
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return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) &&
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sched_asym_prefer(env->dst_cpu, env->src_cpu);
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}
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static inline bool
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voluntary_active_balance(struct lb_env *env)
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{
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struct sched_domain *sd = env->sd;
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if (asym_active_balance(env))
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return 1;
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/*
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* The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
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* It's worth migrating the task if the src_cpu's capacity is reduced
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@ -8858,6 +8862,16 @@ static int need_active_balance(struct lb_env *env)
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if (env->src_grp_type == group_misfit_task)
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return 1;
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return 0;
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}
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static int need_active_balance(struct lb_env *env)
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{
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struct sched_domain *sd = env->sd;
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if (voluntary_active_balance(env))
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return 1;
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return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
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}
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@ -9119,7 +9133,7 @@ more_balance:
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} else
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sd->nr_balance_failed = 0;
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if (likely(!active_balance)) {
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if (likely(!active_balance) || voluntary_active_balance(&env)) {
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/* We were unbalanced, so reset the balancing interval */
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sd->balance_interval = sd->min_interval;
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} else {
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