Re: [Xen-devel] [RFC][PATCH 2/4] sched: change the handling of credits over upper bound

[NISHIGUCHI Naoki <nisiguti@xxxxxxxxxxxxxx>]

I forgot to attach.

NISHIGUCHI Naoki wrote:
> By applying this patch, the credit scheduler don't reset vcpu's credit
> (set to 0) when the credit would be over upper bound. And it prevents a
> vcpu from missing becoming active.
> 
> Best regards,
> Naoki Nishiguchi
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel

diff -r a00eb6595d3c xen/common/sched_credit.c
--- a/xen/common/sched_credit.c Sat Nov 29 09:07:52 2008 +0000
+++ b/xen/common/sched_credit.c Fri Dec 05 17:49:44 2008 +0900
@@ -196,6 +196,7 @@ struct csched_vcpu {
 struct csched_vcpu {
     struct list_head runq_elem;
     struct list_head active_vcpu_elem;
+    struct list_head inactive_vcpu_elem;
     struct csched_dom *sdom;
     struct vcpu *vcpu;
     atomic_t credit;
@@ -231,6 +232,7 @@ struct csched_private {
 struct csched_private {
     spinlock_t lock;
     struct list_head active_sdom;
+    struct list_head inactive_vcpu;
     uint32_t ncpus;
     unsigned int master;
     cpumask_t idlers;
@@ -484,12 +486,9 @@ csched_cpu_pick(struct vcpu *vc)
 }
 
 static inline void
-__csched_vcpu_acct_start(struct csched_vcpu *svc)
+__csched_vcpu_acct_start_locked(struct csched_vcpu *svc)
 {
     struct csched_dom * const sdom = svc->sdom;
-    unsigned long flags;
-
-    spin_lock_irqsave(&csched_priv.lock, flags);
 
     if ( list_empty(&svc->active_vcpu_elem) )
     {
@@ -498,13 +497,22 @@ __csched_vcpu_acct_start(struct csched_v
 
         sdom->active_vcpu_count++;
         list_add(&svc->active_vcpu_elem, &sdom->active_vcpu);
+        list_del_init(&svc->inactive_vcpu_elem);
         if ( list_empty(&sdom->active_sdom_elem) )
         {
             list_add(&sdom->active_sdom_elem, &csched_priv.active_sdom);
             csched_priv.weight += sdom->weight;
         }
     }
-
+}
+
+static inline void
+__csched_vcpu_acct_start(struct csched_vcpu *svc)
+{
+    unsigned long flags;
+
+    spin_lock_irqsave(&csched_priv.lock, flags);
+    __csched_vcpu_acct_start_locked(svc);
     spin_unlock_irqrestore(&csched_priv.lock, flags);
 }
 
@@ -520,6 +528,7 @@ __csched_vcpu_acct_stop_locked(struct cs
 
     sdom->active_vcpu_count--;
     list_del_init(&svc->active_vcpu_elem);
+    list_add(&svc->inactive_vcpu_elem, &csched_priv.inactive_vcpu);
     if ( list_empty(&sdom->active_vcpu) )
     {
         BUG_ON( csched_priv.weight < sdom->weight );
@@ -586,6 +595,7 @@ csched_vcpu_init(struct vcpu *vc)
 
     INIT_LIST_HEAD(&svc->runq_elem);
     INIT_LIST_HEAD(&svc->active_vcpu_elem);
+    INIT_LIST_HEAD(&svc->inactive_vcpu_elem);
     svc->sdom = sdom;
     svc->vcpu = vc;
     atomic_set(&svc->credit, 0);
@@ -621,6 +631,9 @@ csched_vcpu_destroy(struct vcpu *vc)
 
     if ( !list_empty(&svc->active_vcpu_elem) )
         __csched_vcpu_acct_stop_locked(svc);
+
+    if ( !list_empty(&svc->inactive_vcpu_elem) )
+        list_del_init(&svc->inactive_vcpu_elem);
 
     spin_unlock_irqrestore(&csched_priv.lock, flags);
 
@@ -839,6 +852,18 @@ csched_acct(void)
 
     spin_lock_irqsave(&csched_priv.lock, flags);
 
+    /* Add vcpu to active list when its credit were consumed by one tick. */
+    list_for_each_safe( iter_vcpu, next_vcpu, &csched_priv.inactive_vcpu )
+    {
+        svc = list_entry(iter_vcpu, struct csched_vcpu, inactive_vcpu_elem);
+
+        if ( atomic_read(&svc->credit)
+             <= CSCHED_CREDITS_PER_TICK * (CSCHED_TICKS_PER_ACCT - 1) )
+        {
+            __csched_vcpu_acct_start_locked(svc);
+        }
+    }
+
     weight_total = csched_priv.weight;
     credit_total = csched_priv.credit;
 
@@ -995,7 +1020,7 @@ csched_acct(void)
                 if ( credit > CSCHED_CREDITS_PER_TSLICE )
                 {
                     __csched_vcpu_acct_stop_locked(svc);
-                    credit = 0;
+                    credit = CSCHED_CREDITS_PER_TSLICE;
                     atomic_set(&svc->credit, credit);
                 }
             }
@@ -1340,6 +1365,17 @@ csched_dump(void)
             csched_dump_vcpu(svc);
         }
     }
+
+    printk("inactive vcpus:\n");
+    loop = 0;
+    list_for_each( iter_svc, &csched_priv.inactive_vcpu )
+    {
+        struct csched_vcpu *svc;
+        svc = list_entry(iter_svc, struct csched_vcpu, inactive_vcpu_elem);
+
+        printk("\t%3d: ", ++loop);
+        csched_dump_vcpu(svc);
+    }
 }
 
 static void
@@ -1347,6 +1383,7 @@ csched_init(void)
 {
     spin_lock_init(&csched_priv.lock);
     INIT_LIST_HEAD(&csched_priv.active_sdom);
+    INIT_LIST_HEAD(&csched_priv.inactive_vcpu);
     csched_priv.ncpus = 0;
     csched_priv.master = UINT_MAX;
     cpus_clear(csched_priv.idlers);

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