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Message-Id: <20221122203532.15013-3-ricardo.neri-calderon@linux.intel.com>
Date: Tue, 22 Nov 2022 12:35:27 -0800
From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To: "Peter Zijlstra (Intel)" <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>
Cc: Ricardo Neri <ricardo.neri@...el.com>,
"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
Ben Segall <bsegall@...gle.com>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Len Brown <len.brown@...el.com>, Mel Gorman <mgorman@...e.de>,
"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
Steven Rostedt <rostedt@...dmis.org>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Valentin Schneider <vschneid@...hat.com>, x86@...nel.org,
linux-kernel@...r.kernel.org,
Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
"Tim C . Chen" <tim.c.chen@...el.com>
Subject: [PATCH v2 2/7] sched: Prepare sched_asym_prefer() to handle idle state of SMT siblings
The throughput of an SMT sibling decreases if one or more of its siblings
are also busy. Idle, lower-priority cores can help. Thus, it is necessary
to consider the idle state of the SMT siblings of CPUs when selecting by
priority.
In some cases, sched_asym_prefer() does not care about the idle state
(when building sched domains or looking at the priority of the preferred
CPU in a sched group).
Add a new parameter to check the state of the SMT siblings of a CPU when
applicable.
While here, remove a spurious newline.
Cc: Ben Segall <bsegall@...gle.com>
Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Len Brown <len.brown@...el.com>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Tim C. Chen <tim.c.chen@...el.com>
Cc: Valentin Schneider <vschneid@...hat.com>
Cc: x86@...nel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
---
Changes since v1:
* Introduced this patch
---
kernel/sched/fair.c | 17 ++++++++++-------
kernel/sched/sched.h | 8 ++++++--
kernel/sched/topology.c | 6 +++++-
3 files changed, 21 insertions(+), 10 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 18c672ff39ef..d18947a9c03e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8921,7 +8921,7 @@ static bool asym_smt_can_pull_tasks(int dst_cpu, struct sd_lb_stats *sds,
* can help if it has higher priority and is idle (i.e.,
* it has no running tasks).
*/
- return sched_asym_prefer(dst_cpu, sg->asym_prefer_cpu);
+ return sched_asym_prefer(dst_cpu, sg->asym_prefer_cpu, false);
}
/*
@@ -8934,7 +8934,7 @@ static bool asym_smt_can_pull_tasks(int dst_cpu, struct sd_lb_stats *sds,
* exactly one busy CPU. This covers SMT and non-SMT sched groups.
*/
if (sg_busy_cpus == 1 && !sds->local_stat.sum_nr_running)
- return sched_asym_prefer(dst_cpu, sg->asym_prefer_cpu);
+ return sched_asym_prefer(dst_cpu, sg->asym_prefer_cpu, false);
return false;
#else
@@ -8952,7 +8952,8 @@ sched_asym(struct lb_env *env, struct sd_lb_stats *sds, struct sg_lb_stats *sgs
(group->flags & SD_SHARE_CPUCAPACITY))
return asym_smt_can_pull_tasks(env->dst_cpu, sds, sgs, group);
- return sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu);
+ /* Neither env::dst_cpu nor group::asym_prefer_cpu have SMT siblings. */
+ return sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu, false);
}
static inline bool
@@ -9118,7 +9119,9 @@ static bool update_sd_pick_busiest(struct lb_env *env,
case group_asym_packing:
/* Prefer to move from lowest priority CPU's work */
- if (sched_asym_prefer(sg->asym_prefer_cpu, sds->busiest->asym_prefer_cpu))
+ if (sched_asym_prefer(sg->asym_prefer_cpu,
+ sds->busiest->asym_prefer_cpu,
+ false))
return false;
break;
@@ -10060,7 +10063,7 @@ static struct rq *find_busiest_queue(struct lb_env *env,
/* Make sure we only pull tasks from a CPU of lower priority */
if ((env->sd->flags & SD_ASYM_PACKING) &&
- sched_asym_prefer(i, env->dst_cpu) &&
+ sched_asym_prefer(i, env->dst_cpu, true) &&
nr_running == 1)
continue;
@@ -10153,7 +10156,7 @@ asym_active_balance(struct lb_env *env)
* highest priority CPUs.
*/
return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) &&
- sched_asym_prefer(env->dst_cpu, env->src_cpu);
+ sched_asym_prefer(env->dst_cpu, env->src_cpu, true);
}
static inline bool
@@ -10889,7 +10892,7 @@ static void nohz_balancer_kick(struct rq *rq)
* around.
*/
for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) {
- if (sched_asym_prefer(i, cpu)) {
+ if (sched_asym_prefer(i, cpu, true)) {
flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
goto unlock;
}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index a4a20046e586..0fc7c0130755 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -795,8 +795,12 @@ static inline long se_weight(struct sched_entity *se)
return scale_load_down(se->load.weight);
}
-
-static inline bool sched_asym_prefer(int a, int b)
+/*
+ * Used to compare specific CPUs. Also when comparing the preferred CPU of a
+ * sched group or building the sched domains; in such cases checking the state
+ * of SMT siblings, if any, is not needed.
+ */
+static inline bool sched_asym_prefer(int a, int b, bool check_smt)
{
return arch_asym_cpu_priority(a) > arch_asym_cpu_priority(b);
}
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 8739c2a5a54e..8154ef590b9f 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -1282,7 +1282,11 @@ static void init_sched_groups_capacity(int cpu, struct sched_domain *sd)
for_each_cpu(cpu, sched_group_span(sg)) {
if (max_cpu < 0)
max_cpu = cpu;
- else if (sched_asym_prefer(cpu, max_cpu))
+ /*
+ * We want the CPU priorities unaffected by the idle
+ * state of its SMT siblings, if any.
+ */
+ else if (sched_asym_prefer(cpu, max_cpu, false))
max_cpu = cpu;
}
sg->asym_prefer_cpu = max_cpu;
--
2.25.1
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