diff -r 116e2691c071 xen/common/sched_credit.c
--- a/xen/common/sched_credit.c	Thu Jan 22 13:16:49 2009 +0900
+++ b/xen/common/sched_credit.c	Thu Jan 22 13:21:28 2009 +0900
@@ -47,6 +47,7 @@
     (CSCHED_CREDITS_PER_TICK * CSCHED_TICKS_PER_TSLICE)
 #define CSCHED_CREDITS_PER_ACCT     \
     (CSCHED_CREDITS_PER_TICK * CSCHED_TICKS_PER_ACCT)
+#define CSCHED_MSECS_PER_BOOST_TSLICE 2
 
 
 /*
@@ -245,6 +246,7 @@ struct csched_private {
     uint16_t total_percent;
     int credit_balance;
     uint32_t runq_sort;
+    s_time_t boost_tslice;
     CSCHED_STATS_DEFINE()
 };
 
@@ -253,6 +255,10 @@ struct csched_private {
  * Global variables
  */
 static struct csched_private csched_priv;
+
+/* opt_credit_tslice: time slice for BOOST priority */
+static unsigned int opt_credit_tslice = CSCHED_MSECS_PER_BOOST_TSLICE;
+integer_param("credit_tslice", opt_credit_tslice);
 
 static void csched_tick(void *_cpu);
 
@@ -1327,7 +1333,17 @@ csched_schedule(s_time_t now)
     /*
      * Return task to run next...
      */
-    ret.time = MILLISECS(CSCHED_MSECS_PER_TSLICE);
+    if ( snext->pri == CSCHED_PRI_TS_BOOST )
+    {
+        struct csched_vcpu * const svc = __runq_elem(runq->next);
+
+        if ( svc->pri == CSCHED_PRI_TS_BOOST )
+            ret.time = csched_priv.boost_tslice;
+        else
+            ret.time = MILLISECS(CSCHED_MSECS_PER_TICK);
+    }
+    else
+        ret.time = MILLISECS(CSCHED_MSECS_PER_TSLICE);
     ret.task = snext->vcpu;
 
     spc->start_time = now;
@@ -1489,6 +1505,7 @@ csched_init(void)
     csched_priv.runq_sort = 0U;
     csched_priv.percent = 0;
     csched_priv.total_percent = 0;
+    csched_priv.boost_tslice = MILLISECS(opt_credit_tslice);
     CSCHED_STATS_RESET();
 }