linux-kernel - [PATCH 02/10] sched/topology: Provide hooks to allocate data shared per LLC

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Date:   Mon, 22 Oct 2018 07:59:33 -0700
From:   Steve Sistare <steven.sistare@...cle.com>
To:     mingo@...hat.com, peterz@...radead.org
Cc:     subhra.mazumdar@...cle.com, dhaval.giani@...cle.com,
        rohit.k.jain@...cle.com, daniel.m.jordan@...cle.com,
        pavel.tatashin@...rosoft.com, matt@...eblueprint.co.uk,
        umgwanakikbuti@...il.com, riel@...hat.com, jbacik@...com,
        juri.lelli@...hat.com, steven.sistare@...cle.com,
        linux-kernel@...r.kernel.org
Subject: [PATCH 02/10] sched/topology: Provide hooks to allocate data shared per LLC

Add functions sd_llc_alloc_all() and sd_llc_free_all() to allocate and
free data pointed to by struct sched_domain_shared at the last-level-cache
domain.  sd_llc_alloc_all() is called after the SD hierarchy is known, to
eliminate the unnecessary allocations that would occur if we instead
allocated in __sdt_alloc() and then figured out which shared nodes are
redundant.

Signed-off-by: Steve Sistare <steven.sistare@...cle.com>
---
 kernel/sched/topology.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 74 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 505a41c..a2363f6 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -10,6 +10,12 @@
 cpumask_var_t sched_domains_tmpmask;
 cpumask_var_t sched_domains_tmpmask2;
 
+struct s_data;
+static int sd_llc_alloc(struct sched_domain *sd);
+static void sd_llc_free(struct sched_domain *sd);
+static int sd_llc_alloc_all(const struct cpumask *cpu_map, struct s_data *d);
+static void sd_llc_free_all(const struct cpumask *cpu_map);
+
 #ifdef CONFIG_SCHED_DEBUG
 
 static int __init sched_debug_setup(char *str)
@@ -361,8 +367,10 @@ static void destroy_sched_domain(struct sched_domain *sd)
 	 */
 	free_sched_groups(sd->groups, 1);
 
-	if (sd->shared && atomic_dec_and_test(&sd->shared->ref))
+	if (sd->shared && atomic_dec_and_test(&sd->shared->ref)) {
+		sd_llc_free(sd);
 		kfree(sd->shared);
+	}
 	kfree(sd);
 }
 
@@ -993,6 +1001,7 @@ static void __free_domain_allocs(struct s_data *d, enum s_alloc what,
 		free_percpu(d->sd);
 		/* Fall through */
 	case sa_sd_storage:
+		sd_llc_free_all(cpu_map);
 		__sdt_free(cpu_map);
 		/* Fall through */
 	case sa_none:
@@ -1602,6 +1611,62 @@ static void __sdt_free(const struct cpumask *cpu_map)
 	}
 }
 
+static int sd_llc_alloc(struct sched_domain *sd)
+{
+	/* Allocate sd->shared data here. Empty for now. */
+
+	return 0;
+}
+
+static void sd_llc_free(struct sched_domain *sd)
+{
+	struct sched_domain_shared *sds = sd->shared;
+
+	if (!sds)
+		return;
+
+	/* Free data here. Empty for now. */
+}
+
+static int sd_llc_alloc_all(const struct cpumask *cpu_map, struct s_data *d)
+{
+	struct sched_domain *sd, *hsd;
+	int i;
+
+	for_each_cpu(i, cpu_map) {
+		/* Find highest domain that shares resources */
+		hsd = NULL;
+		for (sd = *per_cpu_ptr(d->sd, i); sd; sd = sd->parent) {
+			if (!(sd->flags & SD_SHARE_PKG_RESOURCES))
+				break;
+			hsd = sd;
+		}
+		if (hsd && sd_llc_alloc(hsd))
+			return 1;
+	}
+
+	return 0;
+}
+
+static void sd_llc_free_all(const struct cpumask *cpu_map)
+{
+	struct sched_domain_topology_level *tl;
+	struct sched_domain *sd;
+	struct sd_data *sdd;
+	int j;
+
+	for_each_sd_topology(tl) {
+		sdd = &tl->data;
+		if (!sdd)
+			continue;
+		for_each_cpu(j, cpu_map) {
+			sd = *per_cpu_ptr(sdd->sd, j);
+			if (sd)
+				sd_llc_free(sd);
+		}
+	}
+}
+
 static struct sched_domain *build_sched_domain(struct sched_domain_topology_level *tl,
 		const struct cpumask *cpu_map, struct sched_domain_attr *attr,
 		struct sched_domain *child, int cpu)
@@ -1690,6 +1755,14 @@ static struct sched_domain *build_sched_domain(struct sched_domain_topology_leve
 		}
 	}
 
+	/*
+	 * Allocate shared sd data at last level cache.  Must be done after
+	 * domains are built above, but before the data is used in
+	 * cpu_attach_domain and descendants below.
+	 */
+	if (sd_llc_alloc_all(cpu_map, &d))
+		goto error;
+
 	/* Attach the domains */
 	rcu_read_lock();
 	for_each_cpu(i, cpu_map) {
-- 
1.8.3.1