1.1 --- a/xen/common/sched_credit2.c	Fri Dec 24 08:31:04 2010 +0000
     1.2 +++ b/xen/common/sched_credit2.c	Fri Dec 24 08:31:24 2010 +0000
     1.3 @@ -996,13 +996,14 @@ csched_context_saved(const struct schedu
     1.4      vcpu_schedule_unlock_irq(vc);
     1.5  }
     1.6  
     1.7 -#define MAX_LOAD (1<<30);
     1.8 +#define MAX_LOAD (1ULL<<60);
     1.9  static int
    1.10  choose_cpu(const struct scheduler *ops, struct vcpu *vc)
    1.11  {
    1.12      struct csched_private *prv = CSCHED_PRIV(ops);
    1.13 -    int i, min_load, min_rqi = -1, new_cpu;
    1.14 +    int i, min_rqi = -1, new_cpu;
    1.15      struct csched_vcpu *svc = CSCHED_VCPU(vc);
    1.16 +    s_time_t min_avgload;
    1.17  
    1.18      BUG_ON(cpus_empty(prv->active_queues));
    1.19  
    1.20 @@ -1053,27 +1054,39 @@ choose_cpu(const struct scheduler *ops, 
    1.21  
    1.22      /* FIXME: Pay attention to cpu affinity */                                                                                      
    1.23  
    1.24 -    min_load = MAX_LOAD;
    1.25 +    min_avgload = MAX_LOAD;
    1.26  
    1.27      /* Find the runqueue with the lowest instantaneous load */
    1.28      for_each_cpu_mask(i, prv->active_queues)
    1.29      {
    1.30          struct csched_runqueue_data *rqd;
    1.31 +        s_time_t rqd_avgload;
    1.32  
    1.33          rqd = prv->rqd + i;
    1.34  
    1.35          /* If checking a different runqueue, grab the lock,
    1.36 -         * read the avg, and then release the lock. */
    1.37 -        if ( rqd != svc->rqd
    1.38 -             && ! spin_trylock(&rqd->lock) )
    1.39 +         * read the avg, and then release the lock.
    1.40 +         *
    1.41 +         * If on our own runqueue, don't grab or release the lock;
    1.42 +         * but subtract our own load from the runqueue load to simulate
    1.43 +         * impartiality */
    1.44 +        if ( rqd == svc->rqd )
    1.45 +        {
    1.46 +            rqd_avgload = rqd->b_avgload - svc->avgload;
    1.47 +        }
    1.48 +        else if ( spin_trylock(&rqd->lock) )
    1.49 +        {
    1.50 +            rqd_avgload = rqd->b_avgload;
    1.51 +            spin_unlock(&rqd->lock);
    1.52 +        }
    1.53 +        else
    1.54              continue;
    1.55 -        if ( prv->rqd[i].load < min_load )
    1.56 +
    1.57 +        if ( rqd_avgload < min_avgload )
    1.58          {
    1.59 -            min_load=prv->rqd[i].load;
    1.60 +            min_avgload = rqd_avgload;
    1.61              min_rqi=i;
    1.62          }
    1.63 -        if ( rqd != svc->rqd )
    1.64 -            spin_unlock(&rqd->lock);
    1.65      }
    1.66  
    1.67      /* We didn't find anyone (most likely because of spinlock contention); leave it where it is */