File 58b6fd42-credit2-always-mark-a-tickled-pCPU-as-... of Package xen

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File 58b6fd42-credit2-always-mark-a-tickled-pCPU-as-tickled.patch of Package xen (Revision 579127d54692c0b4a48bd07b6cecf37c)

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# Commit a76645240bd14e964e85dbc975a8989edea6aa27
# Date 2017-03-01 16:56:34 +0000
# Author Dario Faggioli <dario.faggioli@citrix.com>
# Committer George Dunlap <george.dunlap@citrix.com>
xen: credit2: always mark a tickled pCPU as... tickled!

In fact, whether or not a pCPU has been tickled, and is
therefore about to re-schedule, is something we look at
and base decisions on in various places.

So, let's make sure that we do that basing on accurate
information.

While there, also tweak a little bit smt_idle_mask_clear()
(used for implementing SMT support), so that it only alter
the relevant cpumask when there is the actual need for this.
(This is only for reduced overhead, behavior remains the
same).

Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
Reviewed-by: George Dunlap <george.dunlap@eu.citrix.com>

--- a/xen/common/sched_credit2.c
+++ b/xen/common/sched_credit2.c
@@ -491,12 +491,15 @@ void smt_idle_mask_set(unsigned int cpu,
 }
 
 /*
- * Clear the bits of all the siblings of cpu from mask.
+ * Clear the bits of all the siblings of cpu from mask (if necessary).
  */
 static inline
 void smt_idle_mask_clear(unsigned int cpu, cpumask_t *mask)
 {
-    cpumask_andnot(mask, mask, per_cpu(cpu_sibling_mask, cpu));
+    const cpumask_t *cpu_siblings = per_cpu(cpu_sibling_mask, cpu);
+
+    if ( cpumask_subset(cpu_siblings, mask) )
+        cpumask_andnot(mask, mask, per_cpu(cpu_sibling_mask, cpu));
 }
 
 /*
@@ -900,6 +903,14 @@ __runq_remove(struct csched2_vcpu *svc)
 
 void burn_credits(struct csched2_runqueue_data *rqd, struct csched2_vcpu *, s_time_t);
 
+static inline void
+tickle_cpu(unsigned int cpu, struct csched2_runqueue_data *rqd)
+{
+    __cpumask_set_cpu(cpu, &rqd->tickled);
+    smt_idle_mask_clear(cpu, &rqd->smt_idle);
+    cpu_raise_softirq(cpu, SCHEDULE_SOFTIRQ);
+}
+
 /*
  * Check what processor it is best to 'wake', for picking up a vcpu that has
  * just been put (back) in the runqueue. Logic is as follows:
@@ -1067,9 +1078,8 @@ runq_tickle(const struct scheduler *ops,
                     sizeof(d),
                     (unsigned char *)&d);
     }
-    __cpumask_set_cpu(ipid, &rqd->tickled);
-    smt_idle_mask_clear(ipid, &rqd->smt_idle);
-    cpu_raise_softirq(ipid, SCHEDULE_SOFTIRQ);
+
+    tickle_cpu(ipid, rqd);
 
     if ( unlikely(new->tickled_cpu != -1) )
         SCHED_STAT_CRANK(tickled_cpu_overwritten);
@@ -1383,7 +1393,9 @@ csched2_vcpu_sleep(const struct schedule
     SCHED_STAT_CRANK(vcpu_sleep);
 
     if ( curr_on_cpu(vc->processor) == vc )
-        cpu_raise_softirq(vc->processor, SCHEDULE_SOFTIRQ);
+    {
+        tickle_cpu(vc->processor, svc->rqd);
+    }
     else if ( __vcpu_on_runq(svc) )
     {
         ASSERT(svc->rqd == RQD(ops, vc->processor));
@@ -1706,8 +1718,8 @@ static void migrate(const struct schedul
         svc->migrate_rqd = trqd;
         __set_bit(_VPF_migrating, &svc->vcpu->pause_flags);
         __set_bit(__CSFLAG_runq_migrate_request, &svc->flags);
-        cpu_raise_softirq(cpu, SCHEDULE_SOFTIRQ);
         SCHED_STAT_CRANK(migrate_requested);
+        tickle_cpu(cpu, svc->rqd);
     }
     else
     {

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File 58b6fd42-credit2-always-mark-a-tickled-pCPU-as-tickled.patch of Package xen (Revision 579127d54692c0b4a48bd07b6cecf37c)

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