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Message-ID: <20241211185552.4553-9-kprateek.nayak@amd.com>
Date: Wed, 11 Dec 2024 18:55:51 +0000
From: K Prateek Nayak <kprateek.nayak@....com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>, <x86@...nel.org>,
<linux-kernel@...r.kernel.org>
CC: "H. Peter Anvin" <hpa@...or.com>, Dietmar Eggemann
<dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, Ben Segall
<bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, Valentin Schneider
<vschneid@...hat.com>, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>, Tim Chen
<tim.c.chen@...ux.intel.com>, Mario Limonciello <mario.limonciello@....com>,
Meng Li <li.meng@....com>, Huang Rui <ray.huang@....com>, "Gautham R. Shenoy"
<gautham.shenoy@....com>, K Prateek Nayak <kprateek.nayak@....com>
Subject: [RFC PATCH 8/8] sched/fair: Uncache asym_prefer_cpu and find it during update_sd_lb_stats()
On AMD processors supporting dynamic preferred core ranking, the
asym_prefer_cpu cached in sched_group can change dynamically. Since
asym_prefer_cpu is cached when the sched domain hierarchy is built,
updating the cached value across the system would require rebuilding
the sched domain which is prohibitively expensive.
All the asym_prefer_cpu comparisons in the load balancing path are only
carried out post the sched group stats have been updated after iterating
all the CPUs in the group. Uncache the asym_prefer_cpu and compute it
while sched group statistics are being updated as a part of sg_lb_stats.
Fixes: f3a052391822 ("cpufreq: amd-pstate: Enable amd-pstate preferred core support")
Signed-off-by: K Prateek Nayak <kprateek.nayak@....com>
---
kernel/sched/fair.c | 21 +++++++++++++++++++--
kernel/sched/sched.h | 1 -
kernel/sched/topology.c | 15 +--------------
3 files changed, 20 insertions(+), 17 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3f36805ecdca..166b8e831064 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9911,6 +9911,8 @@ struct sg_lb_stats {
unsigned int sum_nr_running; /* Nr of all tasks running in the group */
unsigned int sum_h_nr_running; /* Nr of CFS tasks running in the group */
unsigned int idle_cpus; /* Nr of idle CPUs in the group */
+ unsigned int asym_prefer_cpu; /* CPU with highest asym priority */
+ int highest_asym_prio; /* Asym priority of asym_prefer_cpu */
unsigned int group_weight;
enum group_type group_type;
unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */
@@ -10243,7 +10245,7 @@ sched_group_asym(struct lb_env *env, struct sg_lb_stats *sgs, struct sched_group
(sgs->group_weight - sgs->idle_cpus != 1))
return false;
- return sched_asym(env->sd, env->dst_cpu, group->asym_prefer_cpu);
+ return sched_asym(env->sd, env->dst_cpu, sgs->asym_prefer_cpu);
}
/* One group has more than one SMT CPU while the other group does not */
@@ -10324,6 +10326,17 @@ sched_reduced_capacity(struct rq *rq, struct sched_domain *sd)
return check_cpu_capacity(rq, sd);
}
+static inline void
+update_sg_pick_asym_prefer(struct sg_lb_stats *sgs, int cpu)
+{
+ int asym_prio = arch_asym_cpu_priority(cpu);
+
+ if (asym_prio > sgs->highest_asym_prio) {
+ sgs->asym_prefer_cpu = cpu;
+ sgs->highest_asym_prio = asym_prio;
+ }
+}
+
/**
* update_sg_lb_stats - Update sched_group's statistics for load balancing.
* @env: The load balancing environment.
@@ -10345,6 +10358,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
memset(sgs, 0, sizeof(*sgs));
local_group = group == sds->local;
+ sgs->highest_asym_prio = INT_MIN;
for_each_cpu_and(i, sched_group_span(group), env->cpus) {
struct rq *rq = cpu_rq(i);
@@ -10358,6 +10372,9 @@ static inline void update_sg_lb_stats(struct lb_env *env,
nr_running = rq->nr_running;
sgs->sum_nr_running += nr_running;
+ if (sd_flags & SD_ASYM_PACKING)
+ update_sg_pick_asym_prefer(sgs, i);
+
if (cpu_overutilized(i))
*sg_overutilized = 1;
@@ -10479,7 +10496,7 @@ static bool update_sd_pick_busiest(struct lb_env *env,
case group_asym_packing:
/* Prefer to move from lowest priority CPU's work */
- return sched_asym_prefer(sds->busiest->asym_prefer_cpu, sg->asym_prefer_cpu);
+ return sched_asym_prefer(busiest->asym_prefer_cpu, sgs->asym_prefer_cpu);
case group_misfit_task:
/*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index aef716c41edb..a3f0d326bd11 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2047,7 +2047,6 @@ struct sched_group {
unsigned int group_weight;
unsigned int cores;
struct sched_group_capacity *sgc;
- int asym_prefer_cpu; /* CPU of highest priority in group */
int flags;
/*
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 9c405f0e7b26..20aa087710f0 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -1302,7 +1302,7 @@ static void init_sched_groups_capacity(int cpu, struct sched_domain *sd)
WARN_ON(!sg);
do {
- int cpu, cores = 0, max_cpu = -1;
+ int cpu, cores = 0;
sg->group_weight = cpumask_weight(sched_group_span(sg));
@@ -1314,19 +1314,6 @@ static void init_sched_groups_capacity(int cpu, struct sched_domain *sd)
#endif
}
sg->cores = cores;
-
- if (!(sd->flags & SD_ASYM_PACKING))
- goto next;
-
- for_each_cpu(cpu, sched_group_span(sg)) {
- if (max_cpu < 0)
- max_cpu = cpu;
- else if (sched_asym_prefer(cpu, max_cpu))
- max_cpu = cpu;
- }
- sg->asym_prefer_cpu = max_cpu;
-
-next:
sg = sg->next;
} while (sg != sd->groups);
--
2.34.1
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