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Date: Fri, 23 Feb 2024 11:52:37 +0800
From: kuiliang Shi <seakeel@...il.com>
To: Vincent Guittot <vincent.guittot@...aro.org>, alexs@...nel.org
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
Mel Gorman <mgorman@...e.de>, Daniel Bristot de Oliveira
<bristot@...hat.com>, Valentin Schneider <vschneid@...hat.com>,
"open list:SCHEDULER" <linux-kernel@...r.kernel.org>,
Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Subject: Re: [PATCH v5 3/5] sched/fair: Rework sched_use_asym_prio() and
sched_asym_prefer()
On 2/14/24 12:51 AM, Vincent Guittot wrote:
> On Sat, 10 Feb 2024 at 12:36, <alexs@...nel.org> wrote:
>>
>> From: Alex Shi <alexs@...nel.org>
>>
>> sched_use_asym_prio() and sched_asym_prefer() are used together in various
>> places. Consolidate them into a single function sched_asym().
>>
>> The existing sched_group_asym() is only used when collecting statistics
>
> nit: The existing sched_asym()
Hi Vincent,
Thanks for all reviewing. Do I need to update this for next version? or just fix it during merge?
Alex
>
>> of a scheduling group. Rename it as sched_group_asym(), and remove the
>> obsolete function description.
>>
>> This makes the code easier to read. No functional changes.
>>
>> Tested-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
>> Signed-off-by: Alex Shi <alexs@...nel.org>
>> Cc: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
>> Cc: Valentin Schneider <vschneid@...hat.com>
>> Cc: Vincent Guittot <vincent.guittot@...aro.org>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Reviewed-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
>
> Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>
>
>> ---
>> kernel/sched/fair.c | 45 ++++++++++++++++++++-------------------------
>> 1 file changed, 20 insertions(+), 25 deletions(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 607dc310b355..426eda9eda57 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -9746,8 +9746,18 @@ static bool sched_use_asym_prio(struct sched_domain *sd, int cpu)
>> return sd->flags & SD_SHARE_CPUCAPACITY || is_core_idle(cpu);
>> }
>>
>> +static inline bool sched_asym(struct sched_domain *sd, int dst_cpu, int src_cpu)
>> +{
>> + /*
>> + * First check if @dst_cpu can do asym_packing load balance. Only do it
>> + * if it has higher priority than @src_cpu.
>> + */
>> + return sched_use_asym_prio(sd, dst_cpu) &&
>> + sched_asym_prefer(dst_cpu, src_cpu);
>> +}
>> +
>> /**
>> - * sched_asym - Check if the destination CPU can do asym_packing load balance
>> + * sched_group_asym - Check if the destination CPU can do asym_packing balance
>> * @env: The load balancing environment
>> * @sgs: Load-balancing statistics of the candidate busiest group
>> * @group: The candidate busiest group
>> @@ -9755,34 +9765,21 @@ static bool sched_use_asym_prio(struct sched_domain *sd, int cpu)
>> * @env::dst_cpu can do asym_packing if it has higher priority than the
>> * preferred CPU of @group.
>> *
>> - * SMT is a special case. If we are balancing load between cores, @env::dst_cpu
>> - * can do asym_packing balance only if all its SMT siblings are idle. Also, it
>> - * can only do it if @group is an SMT group and has exactly on busy CPU. Larger
>> - * imbalances in the number of CPUS are dealt with in find_busiest_group().
>> - *
>> - * If we are balancing load within an SMT core, or at PKG domain level, always
>> - * proceed.
>> - *
>> * Return: true if @env::dst_cpu can do with asym_packing load balance. False
>> * otherwise.
>> */
>> static inline bool
>> -sched_asym(struct lb_env *env, struct sg_lb_stats *sgs, struct sched_group *group)
>> +sched_group_asym(struct lb_env *env, struct sg_lb_stats *sgs, struct sched_group *group)
>> {
>> - /* Ensure that the whole local core is idle, if applicable. */
>> - if (!sched_use_asym_prio(env->sd, env->dst_cpu))
>> - return false;
>> -
>> /*
>> - * CPU priorities does not make sense for SMT cores with more than one
>> + * CPU priorities do not make sense for SMT cores with more than one
>> * busy sibling.
>> */
>> - if (group->flags & SD_SHARE_CPUCAPACITY) {
>> - if (sgs->group_weight - sgs->idle_cpus != 1)
>> - return false;
>> - }
>> + if ((group->flags & SD_SHARE_CPUCAPACITY) &&
>> + (sgs->group_weight - sgs->idle_cpus != 1))
>> + return false;
>>
>> - return sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu);
>> + return sched_asym(env->sd, env->dst_cpu, group->asym_prefer_cpu);
>> }
>>
>> /* One group has more than one SMT CPU while the other group does not */
>> @@ -9938,7 +9935,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
>> /* Check if dst CPU is idle and preferred to this group */
>> if (!local_group && env->sd->flags & SD_ASYM_PACKING &&
>> env->idle != CPU_NOT_IDLE && sgs->sum_h_nr_running &&
>> - sched_asym(env, sgs, group)) {
>> + sched_group_asym(env, sgs, group)) {
>> sgs->group_asym_packing = 1;
>> }
>>
>> @@ -11037,8 +11034,7 @@ static struct rq *find_busiest_queue(struct lb_env *env,
>> * SMT cores with more than one busy sibling.
>> */
>> if ((env->sd->flags & SD_ASYM_PACKING) &&
>> - sched_use_asym_prio(env->sd, i) &&
>> - sched_asym_prefer(i, env->dst_cpu) &&
>> + sched_asym(env->sd, i, env->dst_cpu) &&
>> nr_running == 1)
>> continue;
>>
>> @@ -11908,8 +11904,7 @@ static void nohz_balancer_kick(struct rq *rq)
>> * preferred CPU must be idle.
>> */
>> for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) {
>> - if (sched_use_asym_prio(sd, i) &&
>> - sched_asym_prefer(i, cpu)) {
>> + if (sched_asym(sd, i, cpu)) {
>> flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
>> goto unlock;
>> }
>> --
>> 2.43.0
>>
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