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Subject[PATCH 03/10] sched/topology: Provide cfs_overload_cpus bitmap
Date
Define and initialize a sparse bitmap of overloaded CPUs, per
last-level-cache scheduling domain, for use by the CFS scheduling class.
Save a pointer to cfs_overload_cpus in the rq for efficient access.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
include/linux/sched/topology.h | 1 +
kernel/sched/sched.h | 2 ++
kernel/sched/topology.c | 21 +++++++++++++++++++--
3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
index 2634774..8bac15d 100644
--- a/include/linux/sched/topology.h
+++ b/include/linux/sched/topology.h
@@ -72,6 +72,7 @@ struct sched_domain_shared {
atomic_t ref;
atomic_t nr_busy_cpus;
int has_idle_cores;
+ struct sparsemask *cfs_overload_cpus;
};

struct sched_domain {
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 455fa33..aadfe68 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -81,6 +81,7 @@

struct rq;
struct cpuidle_state;
+struct sparsemask;

/* task_struct::on_rq states: */
#define TASK_ON_RQ_QUEUED 1
@@ -805,6 +806,7 @@ struct rq {
struct cfs_rq cfs;
struct rt_rq rt;
struct dl_rq dl;
+ struct sparsemask *cfs_overload_cpus;

#ifdef CONFIG_FAIR_GROUP_SCHED
/* list of leaf cfs_rq on this CPU: */
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index a2363f6..f18c416 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -3,6 +3,7 @@
* Scheduler topology setup/handling methods
*/
#include "sched.h"
+#include <linux/sparsemask.h>

DEFINE_MUTEX(sched_domains_mutex);

@@ -440,6 +441,7 @@ static void update_top_cache_domain(int cpu)
static void
cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
{
+ struct sparsemask *cfs_overload_cpus;
struct rq *rq = cpu_rq(cpu);
struct sched_domain *tmp;

@@ -481,6 +483,10 @@ static void update_top_cache_domain(int cpu)
dirty_sched_domain_sysctl(cpu);
destroy_sched_domains(tmp);

+ sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES);
+ cfs_overload_cpus = (sd ? sd->shared->cfs_overload_cpus : NULL);
+ rcu_assign_pointer(rq->cfs_overload_cpus, cfs_overload_cpus);
+
update_top_cache_domain(cpu);
}

@@ -1611,9 +1617,19 @@ static void __sdt_free(const struct cpumask *cpu_map)
}
}

+#define ZALLOC_MASK(maskp, nelems, node) \
+ (!*(maskp) && !zalloc_sparsemask_node(maskp, nelems, \
+ SPARSEMASK_DENSITY_DEFAULT, \
+ GFP_KERNEL, node)) \
+
static int sd_llc_alloc(struct sched_domain *sd)
{
- /* Allocate sd->shared data here. Empty for now. */
+ struct sched_domain_shared *sds = sd->shared;
+ struct cpumask *span = sched_domain_span(sd);
+ int nid = cpu_to_node(cpumask_first(span));
+
+ if (ZALLOC_MASK(&sds->cfs_overload_cpus, nr_cpu_ids, nid))
+ return 1;

return 0;
}
@@ -1625,7 +1641,8 @@ static void sd_llc_free(struct sched_domain *sd)
if (!sds)
return;

- /* Free data here. Empty for now. */
+ free_sparsemask(sds->cfs_overload_cpus);
+ sds->cfs_overload_cpus = NULL;
}

static int sd_llc_alloc_all(const struct cpumask *cpu_map, struct s_data *d)
--
1.8.3.1
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