linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: "tip-bot2 for Mel Gorman" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Mel Gorman <mgorman@techsingularity.net>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: sched/core] sched/fair: Merge select_idle_core/cpu()
Date: Wed, 17 Feb 2021 13:17:38 -0000	[thread overview]
Message-ID: <161356785893.20312.10270833120354178289.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210127135203.19633-5-mgorman@techsingularity.net>

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     9fe1f127b913318c631d0041ecf71486e38c2c2d
Gitweb:        https://git.kernel.org/tip/9fe1f127b913318c631d0041ecf71486e38c2c2d
Author:        Mel Gorman <mgorman@techsingularity.net>
AuthorDate:    Wed, 27 Jan 2021 13:52:03 
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 17 Feb 2021 14:07:25 +01:00

sched/fair: Merge select_idle_core/cpu()

Both select_idle_core() and select_idle_cpu() do a loop over the same
cpumask. Observe that by clearing the already visited CPUs, we can
fold the iteration and iterate a core at a time.

All we need to do is remember any non-idle CPU we encountered while
scanning for an idle core. This way we'll only iterate every CPU once.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210127135203.19633-5-mgorman@techsingularity.net
---
 kernel/sched/fair.c |  99 +++++++++++++++++++++++++------------------
 1 file changed, 59 insertions(+), 40 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6a0fc8a..c73d588 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6019,6 +6019,14 @@ static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p
 	return new_cpu;
 }
 
+static inline int __select_idle_cpu(int cpu)
+{
+	if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
+		return cpu;
+
+	return -1;
+}
+
 #ifdef CONFIG_SCHED_SMT
 DEFINE_STATIC_KEY_FALSE(sched_smt_present);
 EXPORT_SYMBOL_GPL(sched_smt_present);
@@ -6077,48 +6085,51 @@ unlock:
  * there are no idle cores left in the system; tracked through
  * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
  */
-static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
+static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
 {
-	struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
-	int core, cpu;
+	bool idle = true;
+	int cpu;
 
 	if (!static_branch_likely(&sched_smt_present))
-		return -1;
-
-	if (!test_idle_cores(target, false))
-		return -1;
-
-	cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
+		return __select_idle_cpu(core);
 
-	for_each_cpu_wrap(core, cpus, target) {
-		bool idle = true;
-
-		for_each_cpu(cpu, cpu_smt_mask(core)) {
-			if (!available_idle_cpu(cpu)) {
-				idle = false;
-				break;
+	for_each_cpu(cpu, cpu_smt_mask(core)) {
+		if (!available_idle_cpu(cpu)) {
+			idle = false;
+			if (*idle_cpu == -1) {
+				if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, p->cpus_ptr)) {
+					*idle_cpu = cpu;
+					break;
+				}
+				continue;
 			}
+			break;
 		}
-
-		if (idle)
-			return core;
-
-		cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
+		if (*idle_cpu == -1 && cpumask_test_cpu(cpu, p->cpus_ptr))
+			*idle_cpu = cpu;
 	}
 
-	/*
-	 * Failed to find an idle core; stop looking for one.
-	 */
-	set_idle_cores(target, 0);
+	if (idle)
+		return core;
 
+	cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
 	return -1;
 }
 
 #else /* CONFIG_SCHED_SMT */
 
-static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
+static inline void set_idle_cores(int cpu, int val)
 {
-	return -1;
+}
+
+static inline bool test_idle_cores(int cpu, bool def)
+{
+	return def;
+}
+
+static inline int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
+{
+	return __select_idle_cpu(core);
 }
 
 #endif /* CONFIG_SCHED_SMT */
@@ -6131,10 +6142,11 @@ static inline int select_idle_core(struct task_struct *p, struct sched_domain *s
 static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
 {
 	struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
+	int i, cpu, idle_cpu = -1, nr = INT_MAX;
+	bool smt = test_idle_cores(target, false);
+	int this = smp_processor_id();
 	struct sched_domain *this_sd;
 	u64 time;
-	int this = smp_processor_id();
-	int cpu, nr = INT_MAX;
 
 	this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
 	if (!this_sd)
@@ -6142,7 +6154,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
 
 	cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
 
-	if (sched_feat(SIS_PROP)) {
+	if (sched_feat(SIS_PROP) && !smt) {
 		u64 avg_cost, avg_idle, span_avg;
 
 		/*
@@ -6162,18 +6174,29 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
 	}
 
 	for_each_cpu_wrap(cpu, cpus, target) {
-		if (!--nr)
-			return -1;
-		if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
-			break;
+		if (smt) {
+			i = select_idle_core(p, cpu, cpus, &idle_cpu);
+			if ((unsigned int)i < nr_cpumask_bits)
+				return i;
+
+		} else {
+			if (!--nr)
+				return -1;
+			idle_cpu = __select_idle_cpu(cpu);
+			if ((unsigned int)idle_cpu < nr_cpumask_bits)
+				break;
+		}
 	}
 
-	if (sched_feat(SIS_PROP)) {
+	if (smt)
+		set_idle_cores(this, false);
+
+	if (sched_feat(SIS_PROP) && !smt) {
 		time = cpu_clock(this) - time;
 		update_avg(&this_sd->avg_scan_cost, time);
 	}
 
-	return cpu;
+	return idle_cpu;
 }
 
 /*
@@ -6302,10 +6325,6 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
 	if (!sd)
 		return target;
 
-	i = select_idle_core(p, sd, target);
-	if ((unsigned)i < nr_cpumask_bits)
-		return i;
-
 	i = select_idle_cpu(p, sd, target);
 	if ((unsigned)i < nr_cpumask_bits)
 		return i;

  reply	other threads:[~2021-02-17 13:30 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-27 13:51 [PATCH v5 0/4] Scan for an idle sibling in a single pass Mel Gorman
2021-01-27 13:52 ` [PATCH 1/4] sched/fair: Remove SIS_AVG_CPU Mel Gorman
2021-01-27 13:52 ` [PATCH 2/4] sched/fair: Move avg_scan_cost calculations under SIS_PROP Mel Gorman
2021-01-27 13:52 ` [PATCH 3/4] sched/fair: Remove select_idle_smt() Mel Gorman
2021-01-27 13:52 ` [PATCH 4/4] sched/fair: Merge select_idle_core/cpu() Mel Gorman
2021-02-17 13:17   ` tip-bot2 for Mel Gorman [this message]
2021-02-01  1:13 ` [PATCH v5 0/4] Scan for an idle sibling in a single pass Li, Aubrey
2021-02-01 13:06   ` Mel Gorman

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=161356785893.20312.10270833120354178289.tip-bot2@tip-bot2 \
    --to=tip-bot2@linutronix.de \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-tip-commits@vger.kernel.org \
    --cc=mgorman@techsingularity.net \
    --cc=mingo@kernel.org \
    --cc=peterz@infradead.org \
    --cc=vincent.guittot@linaro.org \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).