[Xen-devel] [PATCH 5/5] domctl: replace cpumask_weight() uses

["Jan Beulich" <JBeulich@xxxxxxxx>]

In one case it could easily be replaced by range checking the result of
a subsequent operation, and in general cpumask_next(), not always
needing to scan the whole bitmap, is more efficient than the specific
uses of cpumask_weight() here. (When running on big systems, operations
on CPU masks aren't cheap enough to use them carelessly.)

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -230,15 +230,15 @@ static unsigned int default_vcpu0_locati
      */
     cpumask_copy(&cpu_exclude_map, per_cpu(cpu_sibling_mask, 0));
     cpu = cpumask_first(&cpu_exclude_map);
-    if ( cpumask_weight(&cpu_exclude_map) > 1 )
-        cpu = cpumask_next(cpu, &cpu_exclude_map);
-    ASSERT(cpu < nr_cpu_ids);
+    i = cpumask_next(cpu, &cpu_exclude_map);
+    if ( i < nr_cpu_ids )
+        cpu = i;
     for_each_cpu(i, online)
     {
         if ( cpumask_test_cpu(i, &cpu_exclude_map) )
             continue;
         if ( (i == cpumask_first(per_cpu(cpu_sibling_mask, i))) &&
-             (cpumask_weight(per_cpu(cpu_sibling_mask, i)) > 1) )
+             (cpumask_next(i, per_cpu(cpu_sibling_mask, i)) < nr_cpu_ids) )
             continue;
         cpumask_or(&cpu_exclude_map, &cpu_exclude_map,
                    per_cpu(cpu_sibling_mask, i));

Attachment: domctl-replace-cpumask_weight.patch
Description: Text document

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel