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Re: [Xen-devel] [PATCH 6 of 6 v2] xen: sched_credit: add some tracing



On 12/12/12 02:52, Dario Faggioli wrote:
About tickling, and PCPU selection.

Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
---
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);
+        }

Hmm, probably should have pointed this out before, but trace_var() is a static inline which checks tb_init_done -- you want __trace_var(). :-)

The rest still looks good.

 -George

+
+        /* 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;
      }


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