[PATCH 6 of 6 v2] xen: sched_credit: add some tracing

[Dario Faggioli <dario.faggioli@citrix.com>]

About tickling, and PCPU selection.

Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
---
Changes from v1:
 * Dummy `struct d {}', accommodating `cpu' only, removed
   in spite of the much more readable `trace_var(..., sizeof(cpu), &cpu)',
   as suggested.

diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
--- a/xen/common/sched_credit.c
+++ b/xen/common/sched_credit.c
@@ -21,6 +21,7 @@
 #include <asm/atomic.h>
 #include <xen/errno.h>
 #include <xen/keyhandler.h>
+#include <xen/trace.h>
 
 
 /*
@@ -97,6 +98,18 @@
 
 
 /*
+ * Credit tracing events ("only" 512 available!). Check
+ * include/public/trace.h for more details.
+ */
+#define TRC_CSCHED_SCHED_TASKLET TRC_SCHED_CLASS_EVT(CSCHED, 1)
+#define TRC_CSCHED_ACCOUNT_START TRC_SCHED_CLASS_EVT(CSCHED, 2)
+#define TRC_CSCHED_ACCOUNT_STOP  TRC_SCHED_CLASS_EVT(CSCHED, 3)
+#define TRC_CSCHED_STOLEN_VCPU   TRC_SCHED_CLASS_EVT(CSCHED, 4)
+#define TRC_CSCHED_PICKED_CPU    TRC_SCHED_CLASS_EVT(CSCHED, 5)
+#define TRC_CSCHED_TICKLE        TRC_SCHED_CLASS_EVT(CSCHED, 6)
+
+
+/*
  * Boot parameters
  */
 static int __read_mostly sched_credit_tslice_ms = CSCHED_DEFAULT_TSLICE_MS;
@@ -315,9 +328,18 @@ static inline void
         }
     }
 
-    /* Send scheduler interrupts to designated CPUs */
     if ( !cpumask_empty(&mask) )
+    {
+        if ( unlikely(tb_init_done) )
+        {
+            /* Avoid TRACE_*: saves checking !tb_init_done each step */
+            for_each_cpu(cpu, &mask)
+                trace_var(TRC_CSCHED_TICKLE, 0, sizeof(cpu), &cpu);
+        }
+
+        /* Send scheduler interrupts to designated CPUs */
         cpumask_raise_softirq(&mask, SCHEDULE_SOFTIRQ);
+    }
 }
 
 static void
@@ -554,6 +576,8 @@ static int
     if ( commit && spc )
        spc->idle_bias = cpu;
 
+    TRACE_3D(TRC_CSCHED_PICKED_CPU, vc->domain->domain_id, vc->vcpu_id, cpu);
+
     return cpu;
 }
 
@@ -586,6 +610,9 @@ static inline void
         }
     }
 
+    TRACE_3D(TRC_CSCHED_ACCOUNT_START, sdom->dom->domain_id,
+             svc->vcpu->vcpu_id, sdom->active_vcpu_count);
+
     spin_unlock_irqrestore(&prv->lock, flags);
 }
 
@@ -608,6 +635,9 @@ static inline void
     {
         list_del_init(&sdom->active_sdom_elem);
     }
+
+    TRACE_3D(TRC_CSCHED_ACCOUNT_STOP, sdom->dom->domain_id,
+             svc->vcpu->vcpu_id, sdom->active_vcpu_count);
 }
 
 static void
@@ -1241,6 +1271,8 @@ csched_runq_steal(int peer_cpu, int cpu,
             if (__csched_vcpu_is_migrateable(vc, cpu))
             {
                 /* We got a candidate. Grab it! */
+                TRACE_3D(TRC_CSCHED_STOLEN_VCPU, peer_cpu,
+                         vc->domain->domain_id, vc->vcpu_id);
                 SCHED_VCPU_STAT_CRANK(speer, migrate_q);
                 SCHED_STAT_CRANK(migrate_queued);
                 WARN_ON(vc->is_urgent);
@@ -1401,6 +1433,7 @@ csched_schedule(
     /* Tasklet work (which runs in idle VCPU context) overrides all else. */
     if ( tasklet_work_scheduled )
     {
+        TRACE_0D(TRC_CSCHED_SCHED_TASKLET);
         snext = CSCHED_VCPU(idle_vcpu[cpu]);
         snext->pri = CSCHED_PRI_TS_BOOST;
     }