[Xen-devel] [PATCH] Fix cpu selection at the time vCPU allocation

["Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx>]

After cpu_[online/offline], set bits in cpu_online_map could be not 
continuous. Use cycle_cpu() to pick the next one.
Signed-off-by: Xiaowei Yang <xiaowei.yang@xxxxxxxxx>

Thanks,
xiaowei

diff -r 310c85c9cb86 xen/common/domctl.c
--- a/xen/common/domctl.c       Mon Mar 02 16:24:50 2009 +0000
+++ b/xen/common/domctl.c       Fri Mar 06 10:07:25 2009 +0800
@@ -428,7 +428,7 @@
 
             cpu = (i == 0) ?
                 default_vcpu0_location() :
-                (d->vcpu[i-1]->processor + 1) % num_online_cpus();
+                cycle_cpu(d->vcpu[i-1]->processor, cpu_online_map);
 
             if ( alloc_vcpu(d, i, cpu) == NULL )
                 goto maxvcpu_out;
diff -r 310c85c9cb86 xen/common/sched_credit.c
--- a/xen/common/sched_credit.c Mon Mar 02 16:24:50 2009 +0000
+++ b/xen/common/sched_credit.c Fri Mar 06 10:07:25 2009 +0800
@@ -248,15 +248,6 @@
 static struct csched_private csched_priv;
 
 static void csched_tick(void *_cpu);
-
-static inline int
-__cycle_cpu(int cpu, const cpumask_t *mask)
-{
-    int nxt = next_cpu(cpu, *mask);
-    if (nxt == NR_CPUS)
-        nxt = first_cpu(*mask);
-    return nxt;
-}
 
 static inline int
 __vcpu_on_runq(struct csched_vcpu *svc)
@@ -428,7 +419,7 @@
     cpus_and(cpus, cpu_online_map, vc->cpu_affinity);
     cpu = cpu_isset(vc->processor, cpus)
             ? vc->processor
-            : __cycle_cpu(vc->processor, &cpus);
+            : cycle_cpu(vc->processor, cpus);
     ASSERT( !cpus_empty(cpus) && cpu_isset(cpu, cpus) );
 
     /*
@@ -454,7 +445,7 @@
         cpumask_t nxt_idlers;
         int nxt;
 
-        nxt = __cycle_cpu(cpu, &cpus);
+        nxt = cycle_cpu(cpu, cpus);
 
         if ( cpu_isset(cpu, cpu_core_map[nxt]) )
         {
@@ -1128,7 +1119,7 @@
 
     while ( !cpus_empty(workers) )
     {
-        peer_cpu = __cycle_cpu(peer_cpu, &workers);
+        peer_cpu = cycle_cpu(peer_cpu, workers);
         cpu_clear(peer_cpu, workers);
 
         /*
diff -r 310c85c9cb86 xen/include/xen/cpumask.h
--- a/xen/include/xen/cpumask.h Mon Mar 02 16:24:50 2009 +0000
+++ b/xen/include/xen/cpumask.h Fri Mar 06 10:07:25 2009 +0800
@@ -38,6 +38,8 @@
  *
  * int first_cpu(mask)                 Number lowest set bit, or NR_CPUS
  * int next_cpu(cpu, mask)             Next cpu past 'cpu', or NR_CPUS
+ * int last_cpu(mask)                  Number highest set bit, or NR_CPUS
+ * int cycle_cpu(cpu, mask)            Next cpu cycling from 'cpu', or NR_CPUS
  *
  * cpumask_t cpumask_of_cpu(cpu)       Return cpumask with bit 'cpu' set
  * CPU_MASK_ALL                                Initializer - all bits set
@@ -225,10 +227,21 @@
 #define last_cpu(src) __last_cpu(&(src), NR_CPUS)
 static inline int __last_cpu(const cpumask_t *srcp, int nbits)
 {
-       int cpu, pcpu = NR_CPUS;
-       for (cpu = first_cpu(*srcp); cpu < NR_CPUS; cpu = next_cpu(cpu, *srcp))
+       int cpu, pcpu = nbits;
+       for (cpu = __first_cpu(srcp, nbits);
+            cpu < nbits;
+            cpu = __next_cpu(cpu, srcp, nbits))
                pcpu = cpu;
        return pcpu;
+}
+
+#define cycle_cpu(n, src) __cycle_cpu((n), &(src), NR_CPUS)
+static inline int __cycle_cpu(int n, const cpumask_t *srcp, int nbits)
+{
+    int nxt = __next_cpu(n, srcp, nbits);
+    if (nxt == nbits)
+        nxt = __first_cpu(srcp, nbits);
+    return nxt;
 }
 
 #define cpumask_of_cpu(cpu)                                            \

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