[Xen-devel] [PATCH v2 08/16] xen: derive NUMA node affinity from hard and soft CPU affinity

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

if a domain's NUMA node-affinity (which is what controls
memory allocations) is provided by the user/toolstack, it
just is not touched. However, if the user does not say
anything, leaving it all to Xen, let's compute it in the
following way:

 1. cpupool's cpus & hard-affinity & soft-affinity
 2. if (1) is empty: cpupool's cpus & hard-affinity

This guarantees memory to be allocated from the narrowest
possible set of NUMA nodes, ad makes it relatively easy to
set up NUMA-aware scheduling on top of soft affinity.

Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
---
 xen/common/domain.c |   22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 2916490..4b8fca8 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -353,7 +353,7 @@ struct domain *domain_create(
 
 void domain_update_node_affinity(struct domain *d)
 {
-    cpumask_var_t cpumask;
+    cpumask_var_t cpumask, cpumask_soft;
     cpumask_var_t online_affinity;
     const cpumask_t *online;
     struct vcpu *v;
@@ -361,9 +361,15 @@ void domain_update_node_affinity(struct domain *d)
 
     if ( !zalloc_cpumask_var(&cpumask) )
         return;
+    if ( !zalloc_cpumask_var(&cpumask_soft) )
+    {
+        free_cpumask_var(cpumask);
+        return;
+    }
     if ( !alloc_cpumask_var(&online_affinity) )
     {
         free_cpumask_var(cpumask);
+        free_cpumask_var(cpumask_soft);
         return;
     }
 
@@ -373,8 +379,12 @@ void domain_update_node_affinity(struct domain *d)
 
     for_each_vcpu ( d, v )
     {
+        /* Build up the mask of online pcpus we have hard affinity with */
         cpumask_and(online_affinity, v->cpu_hard_affinity, online);
         cpumask_or(cpumask, cpumask, online_affinity);
+
+        /* As well as the mask of all pcpus we have soft affinity with */
+        cpumask_or(cpumask_soft, cpumask_soft, v->cpu_soft_affinity);
     }
 
     /*
@@ -386,6 +396,15 @@ void domain_update_node_affinity(struct domain *d)
      */
     if ( d->auto_node_affinity )
     {
+        /*
+         * We're looking for the narower possible set of nodes. So, if
+         * possible (i.e., if not empty!) let's use the intersection
+         * between online, hard and soft affinity. If not, just fall back
+         * to online & hard affinity.
+         */
+        if ( cpumask_intersects(cpumask, cpumask_soft) )
+            cpumask_and(cpumask, cpumask, cpumask_soft);
+
         nodes_clear(d->node_affinity);
         for_each_online_node ( node )
             if ( cpumask_intersects(&node_to_cpumask(node), cpumask) )
@@ -397,6 +416,7 @@ void domain_update_node_affinity(struct domain *d)
     spin_unlock(&d->node_affinity_lock);
 
     free_cpumask_var(online_affinity);
+    free_cpumask_var(cpumask_soft);
     free_cpumask_var(cpumask);
 }
 


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