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Date: Wed, 20 Jul 2022 13:14:59 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Yicong Yang <yangyicong@...ilicon.com>
Cc: mingo@...hat.com, juri.lelli@...hat.com,
vincent.guittot@...aro.org, tim.c.chen@...ux.intel.com,
gautham.shenoy@....com, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, dietmar.eggemann@....com,
rostedt@...dmis.org, bsegall@...gle.com, bristot@...hat.com,
prime.zeng@...wei.com, jonathan.cameron@...wei.com,
ego@...ux.vnet.ibm.com, srikar@...ux.vnet.ibm.com,
linuxarm@...wei.com, 21cnbao@...il.com, guodong.xu@...aro.org,
hesham.almatary@...wei.com, john.garry@...wei.com,
shenyang39@...wei.com, kprateek.nayak@....com, yu.c.chen@...el.com,
wuyun.abel@...edance.com
Subject: Re: [RESEND PATCH v5 2/2] sched/fair: Scan cluster before scanning
LLC in wake-up path
On Wed, Jul 20, 2022 at 04:11:50PM +0800, Yicong Yang wrote:
> + /* TODO: Support SMT system with cluster topology */
> + if (!sched_smt_active() && sd) {
> + for_each_cpu_and(cpu, cpus, sched_domain_span(sd)) {
So that's no SMT and no wrap iteration..
Does something like this work?
---
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6437,6 +6437,30 @@ static int select_idle_cpu(struct task_s
}
}
+ if (IS_ENABLED(CONFIG_SCHED_CLUSTER) &&
+ static_branch_unlikely(&sched_cluster_active)) {
+ struct sched_domain *sdc = rcu_dereference(per_cpu(sd_cluster, target));
+ if (sdc) {
+ for_each_cpu_wrap(cpu, sched_domain_span(sdc), target + 1) {
+ if (!cpumask_test_cpu(cpu, cpus))
+ continue;
+
+ if (has_idle_core) {
+ i = select_idle_core(p, cpu, cpus, &idle_cpu);
+ if ((unsigned int)i < nr_cpumask_bits)
+ return i;
+ } else {
+ if (--nr <= 0)
+ return -1;
+ idle_cpu = __select_idle_cpu(cpu, p);
+ if ((unsigned int)idle_cpu < nr_cpumask_bits)
+ break;
+ }
+ }
+ cpumask_andnot(cpus, cpus, sched_domain_span(sdc));
+ }
+ }
+
for_each_cpu_wrap(cpu, cpus, target + 1) {
if (has_idle_core) {
i = select_idle_core(p, cpu, cpus, &idle_cpu);
@@ -6444,7 +6468,7 @@ static int select_idle_cpu(struct task_s
return i;
} else {
- if (!--nr)
+ if (--nr <= 0)
return -1;
idle_cpu = __select_idle_cpu(cpu, p);
if ((unsigned int)idle_cpu < nr_cpumask_bits)
@@ -6543,7 +6567,7 @@ static int select_idle_sibling(struct ta
/*
* If the previous CPU is cache affine and idle, don't be stupid:
*/
- if (prev != target && cpus_share_cache(prev, target) &&
+ if (prev != target && cpus_share_lowest_cache(prev, target) &&
(available_idle_cpu(prev) || sched_idle_cpu(prev)) &&
asym_fits_capacity(task_util, prev))
return prev;
@@ -6569,7 +6593,7 @@ static int select_idle_sibling(struct ta
p->recent_used_cpu = prev;
if (recent_used_cpu != prev &&
recent_used_cpu != target &&
- cpus_share_cache(recent_used_cpu, target) &&
+ cpus_share_lowest_cache(recent_used_cpu, target) &&
(available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) &&
cpumask_test_cpu(p->recent_used_cpu, p->cpus_ptr) &&
asym_fits_capacity(task_util, recent_used_cpu)) {
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1813,7 +1813,9 @@ DECLARE_PER_CPU(struct sched_domain __rc
DECLARE_PER_CPU(struct sched_domain __rcu *, sd_numa);
DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing);
DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_cpucapacity);
+
extern struct static_key_false sched_asym_cpucapacity;
+extern struct static_key_false sched_cluster_active;
struct sched_group_capacity {
atomic_t ref;
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -670,7 +670,9 @@ DEFINE_PER_CPU(struct sched_domain_share
DEFINE_PER_CPU(struct sched_domain __rcu *, sd_numa);
DEFINE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing);
DEFINE_PER_CPU(struct sched_domain __rcu *, sd_asym_cpucapacity);
+
DEFINE_STATIC_KEY_FALSE(sched_asym_cpucapacity);
+DEFINE_STATIC_KEY_FALSE(sched_cluster_active);
static void update_top_cache_domain(int cpu)
{
@@ -2268,6 +2270,7 @@ build_sched_domains(const struct cpumask
struct rq *rq = NULL;
int i, ret = -ENOMEM;
bool has_asym = false;
+ bool has_cluster = false;
if (WARN_ON(cpumask_empty(cpu_map)))
goto error;
@@ -2289,6 +2292,7 @@ build_sched_domains(const struct cpumask
sd = build_sched_domain(tl, cpu_map, attr, sd, i);
has_asym |= sd->flags & SD_ASYM_CPUCAPACITY;
+ has_cluster |= sd->flags & SD_CLUSTER;
if (tl == sched_domain_topology)
*per_cpu_ptr(d.sd, i) = sd;
@@ -2399,6 +2403,9 @@ build_sched_domains(const struct cpumask
if (has_asym)
static_branch_inc_cpuslocked(&sched_asym_cpucapacity);
+ if (has_cluster)
+ static_branch_inc_cpuslocked(&sched_cluster_active);
+
if (rq && sched_debug_verbose) {
pr_info("root domain span: %*pbl (max cpu_capacity = %lu)\n",
cpumask_pr_args(cpu_map), rq->rd->max_cpu_capacity);
@@ -2498,6 +2505,9 @@ static void detach_destroy_domains(const
if (rcu_access_pointer(per_cpu(sd_asym_cpucapacity, cpu)))
static_branch_dec_cpuslocked(&sched_asym_cpucapacity);
+ if (rcu_access_pointer(per_cpu(sd_cluster, cpu)))
+ static_branch_dec_cpuslocked(&sched_cluster_active);
+
rcu_read_lock();
for_each_cpu(i, cpu_map)
cpu_attach_domain(NULL, &def_root_domain, i);
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