[Xen-devel] [PATCH 08/15] xen: numa-sched: make space for per-vcpu node-affinity

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

Before this change, each vcpu had its own vcpu-affinity (also
called pinning), while the whole domain had a NUMA node-affinity.
Of course, as the (credit) scheduler schedules vcpus and not
whole domains, this means that all the vcpus of a domain had
the same NUMA node-affinity.

This change is the first step toward overcoming such limitation.
It adds the data structures for storing the node-affinity on a
per-vcpu basis (along with allocating and initializing it).

As far as this change only is concerned, there is no specific
way to change the node-affinity of a vcpu to something which
is not automatically computed (basing on its vcpu-affinity).
Such logic is being introduced in subsequent commits.

Also, now that each vcpu has its own node-affinity, and in
case the domain's node-affinity is set to 'automatically
computed', we build it up as the union of all the
node-affinities of all the vcpus of the domain.

Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
---
 xen/common/domain.c     |   39 ++++++++++++++++++++++++++++++++-----
 xen/common/keyhandler.c |    6 +++++-
 xen/common/schedule.c   |   50 +++++++++++++++++++++++++++++++++++++++++++++++
 xen/include/xen/sched.h |   10 +++++++++
 4 files changed, 99 insertions(+), 6 deletions(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index af31ab4..8d2ff49 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -128,6 +128,7 @@ struct vcpu *alloc_vcpu(
     if ( !zalloc_cpumask_var(&v->cpu_affinity) ||
          !zalloc_cpumask_var(&v->cpu_affinity_tmp) ||
          !zalloc_cpumask_var(&v->cpu_affinity_saved) ||
+         !zalloc_cpumask_var(&v->node_affinity) ||
          !zalloc_cpumask_var(&v->vcpu_dirty_cpumask) )
         goto fail_free;
 
@@ -159,6 +160,7 @@ struct vcpu *alloc_vcpu(
         free_cpumask_var(v->cpu_affinity);
         free_cpumask_var(v->cpu_affinity_tmp);
         free_cpumask_var(v->cpu_affinity_saved);
+        free_cpumask_var(v->node_affinity);
         free_cpumask_var(v->vcpu_dirty_cpumask);
         free_vcpu_struct(v);
         return NULL;
@@ -353,7 +355,7 @@ void domain_update_node_affinity(struct domain *d)
     cpumask_var_t online_affinity;
     const cpumask_t *online;
     struct vcpu *v;
-    unsigned int node;
+    unsigned int cpu;
 
     if ( !zalloc_cpumask_var(&cpumask) )
         return;
@@ -367,9 +369,36 @@ void domain_update_node_affinity(struct domain *d)
 
     spin_lock(&d->node_affinity_lock);
 
+    /*
+     * Let's prepare the cpumask that will be used below to actually update
+     * the node-affinity of the whole domain. Each vcpu has a vcpu-affinity
+     * and a numa-affinity. What gets built in cpumask (and used below) is
+     * the union of all the (online) cpus in all the vcpu's numa-affinity
+     * masks.
+     *
+     * On its turn, the numa-affinity mask of the i-eth vcpu (say, 'v') is
+     * either derived directly from the vcpu's vcpu-affinity mask (in case
+     * v->auto_node_affinity is true) or has its own value, (potentially)
+     * completely independent from v->cpu_affinity. In the former case, it
+     * is here that we make sure the two affinity masks matches (since this
+     * function gets called in correspondence of each modification to
+     * v->cpu_affinity happening in vcpu_set_affinity() ); in the latter
+     * case, we just leave v->node_affinity alone.
+     */
     for_each_vcpu ( d, v )
     {
-        cpumask_and(online_affinity, v->cpu_affinity, online);
+        if ( v->auto_node_affinity )
+        {
+            cpumask_clear(v->node_affinity);
+            for_each_cpu ( cpu, v->cpu_affinity )
+                cpumask_or(v->node_affinity, v->node_affinity,
+                           &node_to_cpumask(cpu_to_node(cpu)));
+
+            cpumask_and(online_affinity, v->node_affinity, online);
+        }
+        else
+            cpumask_copy(online_affinity, v->node_affinity);
+
         cpumask_or(cpumask, cpumask, online_affinity);
     }
 
@@ -383,9 +412,8 @@ void domain_update_node_affinity(struct domain *d)
     if ( d->auto_node_affinity )
     {
         nodes_clear(d->node_affinity);
-        for_each_online_node ( node )
-            if ( cpumask_intersects(&node_to_cpumask(node), cpumask) )
-                node_set(node, d->node_affinity);
+        for_each_cpu ( cpu, cpumask )
+            node_set(cpu_to_node(cpu), d->node_affinity);
     }
 
     sched_set_node_affinity(d, &d->node_affinity);
@@ -734,6 +762,7 @@ static void complete_domain_destroy(struct rcu_head *head)
         {
             free_cpumask_var(v->cpu_affinity);
             free_cpumask_var(v->cpu_affinity_tmp);
+            free_cpumask_var(v->node_affinity);
             free_cpumask_var(v->vcpu_dirty_cpumask);
             free_vcpu_struct(v);
         }
diff --git a/xen/common/keyhandler.c b/xen/common/keyhandler.c
index b9ad1b5..8f844bc 100644
--- a/xen/common/keyhandler.c
+++ b/xen/common/keyhandler.c
@@ -297,7 +297,11 @@ static void dump_domains(unsigned char key)
             cpuset_print(tmpstr, sizeof(tmpstr), v->vcpu_dirty_cpumask);
             printk("dirty_cpus=%s ", tmpstr);
             cpuset_print(tmpstr, sizeof(tmpstr), v->cpu_affinity);
-            printk("cpu_affinity=%s\n", tmpstr);
+            printk("cpu_affinity=%s ", tmpstr);
+            cpuset_print(tmpstr, sizeof(tmpstr), v->node_affinity);
+            printk("node_affinity=%s%s\n",
+                   v->auto_node_affinity ? "(auto)" : "(manual)",
+                   tmpstr);
             printk("    pause_count=%d pause_flags=%lx\n",
                    atomic_read(&v->pause_count), v->pause_flags);
             arch_dump_vcpu_info(v);
diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index a8398bd..04f0a38 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -200,6 +200,9 @@ int sched_init_vcpu(struct vcpu *v, unsigned int processor)
     else
         cpumask_setall(v->cpu_affinity);
 
+    v->auto_node_affinity = 1;
+    cpumask_copy(v->node_affinity, v->cpu_affinity);
+
     /* Initialise the per-vcpu timers. */
     init_timer(&v->periodic_timer, vcpu_periodic_timer_fn,
                v, v->processor);
@@ -676,6 +679,53 @@ int vcpu_set_affinity(struct vcpu *v, const cpumask_t 
*affinity)
     return 0;
 }
 
+int vcpu_set_node_affinity(struct vcpu *v, const nodemask_t *nodes)
+{
+    nodemask_t online_nodes;
+    int node;
+
+    nodes_and(online_nodes, node_online_map, *nodes);
+
+    /* Having no affinity at all is just wrong */
+    if ( nodes_empty(online_nodes) )
+        return -EINVAL;
+
+    spin_lock(&v->domain->node_affinity_lock);
+
+    /*
+     * Explicitly saying "all nodes" is not particularly useful here.
+     * Let's use it as the `reset numa-affinity to auto' command.
+     */
+    if ( nodes_full(*nodes) )
+    {
+        v->auto_node_affinity = 1;
+        goto out;
+    }
+
+    /*
+     * When someone asks for a specific numa-affinity for a vcpu we need to
+     * clear auto_node_affinity, convert the nodemask in online_nodes
+     * into a cpumask_t and store it in node_affinity.
+     */
+    v->auto_node_affinity = 0;
+
+    cpumask_clear(v->node_affinity);
+    for_each_node_mask( node, online_nodes )
+        cpumask_or(v->node_affinity, v->node_affinity,
+                   &node_to_cpumask(node));
+
+out:
+    spin_unlock(&v->domain->node_affinity_lock);
+
+    /*
+     * Changing the numa-affinity of a vcpu calls for an update
+     * of the node-affinity of the whole domain.
+     */
+    domain_update_node_affinity(v->domain);
+
+    return 0;
+}
+
 /* Block the currently-executing domain until a pertinent event occurs. */
 void vcpu_block(void)
 {
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 0013a8d..c46487e 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -156,6 +156,8 @@ struct vcpu
     /* VCPU need affinity restored */
     bool_t           affinity_broken;
 
+    /* is node_affinity (below) automatically computed from vcpu-affinity? */
+    bool_t           auto_node_affinity;
 
     /*
      * > 0: a single port is being polled;
@@ -181,6 +183,13 @@ struct vcpu
     /* Used to restore affinity across S3. */
     cpumask_var_t    cpu_affinity_saved;
 
+    /*
+     * Bitmask of CPUs on which this VCPU prefers to run. For both this
+     * and auto_node_affinity access is serialized against
+     * v->domain->node_affinity_lock.
+     */
+    cpumask_var_t    node_affinity;
+
     /* Bitmask of CPUs which are holding onto this VCPU's state. */
     cpumask_var_t    vcpu_dirty_cpumask;
 
@@ -708,6 +717,7 @@ int schedule_cpu_switch(unsigned int cpu, struct cpupool 
*c);
 void vcpu_force_reschedule(struct vcpu *v);
 int cpu_disable_scheduler(unsigned int cpu);
 int vcpu_set_affinity(struct vcpu *v, const cpumask_t *affinity);
+int vcpu_set_node_affinity(struct vcpu *v, const nodemask_t *nodes);
 void restore_vcpu_affinity(struct domain *d);
 
 void vcpu_runstate_get(struct vcpu *v, struct vcpu_runstate_info *runstate);


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