[Xen-devel] [PATCH v4 42/46] xen/sched: support multiple cpus per scheduling resource

[Juergen Gross <jgross@xxxxxxxx>]

Prepare supporting multiple cpus per scheduling resource by allocating
the cpumask per resource dynamically.

Modify sched_res_mask to have only one bit per scheduling resource set.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V1: new patch (carved out from other patch)
V4:
- use cpumask_t for sched_res_mask (Jan Beulich)
- clear cpu in sched_res_mask when taking cpu away (Jan Beulich)
---
 xen/common/cpupool.c       |  4 ++--
 xen/common/schedule.c      | 15 +++++++++++++--
 xen/include/xen/sched-if.h |  4 ++--
 3 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/xen/common/cpupool.c b/xen/common/cpupool.c
index 7228ca84b4..13dffaadcf 100644
--- a/xen/common/cpupool.c
+++ b/xen/common/cpupool.c
@@ -283,7 +283,7 @@ static int cpupool_assign_cpu_locked(struct cpupool *c, 
unsigned int cpu)
         cpupool_cpu_moving = NULL;
     }
     cpumask_set_cpu(cpu, c->cpu_valid);
-    cpumask_and(c->res_valid, c->cpu_valid, sched_res_mask);
+    cpumask_and(c->res_valid, c->cpu_valid, &sched_res_mask);
 
     rcu_read_lock(&domlist_read_lock);
     for_each_domain_in_cpupool(d, c)
@@ -376,7 +376,7 @@ static int cpupool_unassign_cpu_start(struct cpupool *c, 
unsigned int cpu)
     atomic_inc(&c->refcnt);
     cpupool_cpu_moving = c;
     cpumask_clear_cpu(cpu, c->cpu_valid);
-    cpumask_and(c->res_valid, c->cpu_valid, sched_res_mask);
+    cpumask_and(c->res_valid, c->cpu_valid, &sched_res_mask);
 
 out:
     spin_unlock(&cpupool_lock);
diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index c14a66d5f0..bab24104cd 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -61,7 +61,7 @@ integer_param("sched_ratelimit_us", sched_ratelimit_us);
 
 /* Number of vcpus per struct sched_unit. */
 bool __read_mostly sched_disable_smt_switching;
-const cpumask_t *sched_res_mask = &cpumask_all;
+cpumask_t sched_res_mask;
 
 /* Common lock for free cpus. */
 static DEFINE_SPINLOCK(sched_free_cpu_lock);
@@ -2411,8 +2411,14 @@ static int cpu_schedule_up(unsigned int cpu)
     sr = xzalloc(struct sched_resource);
     if ( sr == NULL )
         return -ENOMEM;
+    if ( !zalloc_cpumask_var(&sr->cpus) )
+    {
+        xfree(sr);
+        return -ENOMEM;
+    }
+
     sr->master_cpu = cpu;
-    sr->cpus = cpumask_of(cpu);
+    cpumask_copy(sr->cpus, cpumask_of(cpu));
     set_sched_res(cpu, sr);
 
     sr->scheduler = &sched_idle_ops;
@@ -2424,6 +2430,8 @@ static int cpu_schedule_up(unsigned int cpu)
     /* We start with cpu granularity. */
     sr->granularity = 1;
 
+    cpumask_set_cpu(cpu, &sched_res_mask);
+
     /* Boot CPU is dealt with later in scheduler_init(). */
     if ( cpu == 0 )
         return 0;
@@ -2456,6 +2464,7 @@ static void sched_res_free(struct rcu_head *head)
 {
     struct sched_resource *sr = container_of(head, struct sched_resource, rcu);
 
+    free_cpumask_var(sr->cpus);
     xfree(sr);
 }
 
@@ -2469,7 +2478,9 @@ static void cpu_schedule_down(unsigned int cpu)
 
     kill_timer(&sr->s_timer);
 
+    cpumask_clear_cpu(cpu, &sched_res_mask);
     set_sched_res(cpu, NULL);
+
     call_rcu(&sr->rcu, sched_res_free);
 
     rcu_read_unlock(&sched_res_rculock);
diff --git a/xen/include/xen/sched-if.h b/xen/include/xen/sched-if.h
index 3988985ee6..780735dda3 100644
--- a/xen/include/xen/sched-if.h
+++ b/xen/include/xen/sched-if.h
@@ -24,7 +24,7 @@ extern cpumask_t cpupool_free_cpus;
 extern int sched_ratelimit_us;
 
 /* Scheduling resource mask. */
-extern const cpumask_t *sched_res_mask;
+extern cpumask_t sched_res_mask;
 
 /* Number of vcpus per struct sched_unit. */
 enum sched_gran {
@@ -57,7 +57,7 @@ struct sched_resource {
     /* Cpu with lowest id in scheduling resource. */
     unsigned int        master_cpu;
     unsigned int        granularity;
-    const cpumask_t    *cpus;           /* cpus covered by this struct     */
+    cpumask_var_t       cpus;           /* cpus covered by this struct     */
     struct rcu_head     rcu;
 };
 
-- 
2.16.4


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