diff -r 64618a20b9de xen/common/sched_credit.c
--- a/xen/common/sched_credit.c	Thu Jan 22 13:22:54 2009 +0900
+++ b/xen/common/sched_credit.c	Thu Jan 22 13:42:04 2009 +0900
@@ -202,6 +202,7 @@ struct csched_vcpu {
     struct csched_dom *sdom;
     struct vcpu *vcpu;
     atomic_t credit;
+    atomic_t boost_credit;
     int prev_credit;
     uint16_t flags;
     int16_t pri;
@@ -549,14 +550,6 @@ csched_vcpu_acct(unsigned int cpu)
     ASSERT( svc->sdom != NULL );
 
     /*
-     * If this VCPU's priority was boosted when it last awoke, reset it.
-     * If the VCPU is found here, then it's consuming a non-negligeable
-     * amount of CPU resources and should no longer be boosted.
-     */
-    if ( svc->pri == CSCHED_PRI_TS_BOOST )
-        svc->pri = CSCHED_PRI_TS_UNDER;
-
-    /*
      * If it's been active a while, check if we'd be better off
      * migrating it to run elsewhere (see multi-core and multi-thread
      * support in csched_cpu_pick()).
@@ -591,6 +584,7 @@ csched_vcpu_init(struct vcpu *vc)
     svc->sdom = sdom;
     svc->vcpu = vc;
     atomic_set(&svc->credit, 0);
+    atomic_set(&svc->boost_credit, 0);
     svc->prev_credit = 0;
     svc->flags = 0U;
     svc->pri = is_idle_domain(dom) ? CSCHED_PRI_IDLE : CSCHED_PRI_TS_UNDER;
@@ -706,6 +700,8 @@ csched_vcpu_wake(struct vcpu *vc)
          !(svc->flags & CSCHED_FLAG_VCPU_PARKED) )
     {
         svc->pri = CSCHED_PRI_TS_BOOST;
+        atomic_add(CSCHED_CREDITS_PER_TICK, &svc->boost_credit);
+        atomic_sub(CSCHED_CREDITS_PER_TICK, &svc->credit);
     }
 
     /* Put the VCPU on the runq and tickle CPUs */
@@ -954,11 +950,14 @@ csched_acct(void)
         credit_sum = 0;
         list_for_each_safe( iter_vcpu, next_vcpu, &sdom->active_vcpu )
         {
-            int adjust;
+            int adjust, boost_credit;
 
             svc = list_entry(iter_vcpu, struct csched_vcpu, active_vcpu_elem);
             BUG_ON( sdom != svc->sdom );
 
+            boost_credit = atomic_read(&svc->boost_credit);
+            atomic_set(&svc->boost_credit, 0);
+            atomic_add(boost_credit, &svc->credit);
             credit = atomic_read(&svc->credit);
             adjust = svc->prev_credit - credit - CSCHED_CREDITS_PER_TSLICE;
             if ( adjust > 0 )
@@ -1290,6 +1289,22 @@ csched_schedule(s_time_t now)
                ) /
                ( MILLISECS(CSCHED_MSECS_PER_TSLICE) /
                  CSCHED_CREDITS_PER_TSLICE );
+    if ( scurr->pri == CSCHED_PRI_TS_BOOST )
+    {
+        int boost_credit = atomic_read(&scurr->boost_credit);
+
+        if ( boost_credit > consumed )
+        {
+            atomic_sub(consumed, &scurr->boost_credit);
+            consumed = 0;
+        }
+        else
+        {
+            atomic_sub(boost_credit, &scurr->boost_credit);
+            consumed -= boost_credit;
+            scurr->pri = CSCHED_PRI_TS_UNDER;
+        }
+    }
     if ( consumed > 0 && !is_idle_vcpu(current) )
         atomic_sub(consumed, &scurr->credit);
 
@@ -1366,8 +1381,9 @@ csched_dump_vcpu(struct csched_vcpu *svc
 
     if ( sdom )
     {
-        printk(" credit=%i [w=%u,p=%u]",
+        printk(" credit=%i bc=%i [w=%u,p=%u]",
                atomic_read(&svc->credit),
+               atomic_read(&svc->boost_credit),
                sdom->weight,
                sdom->percent);
 #ifdef CSCHED_STATS