xen: tracing: add trace records for schedule and rate-limiting.

As far as {csched, csched2, rt}_schedule() are concerned,
an "empty" event, would already make it easier to read and
understand a trace.

But while there, add a few useful information, like
if the cpu that is going through the scheduler has
been tickled or not, if it is currently idle, etc
(they vary, on a per-scheduler basis).

For Credit1 and Credit2, add a record about when
rate-limiting kicks in too.

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

xen/common/sched_credit.c

@@ -133,6 +133,8 @@
 #define TRC_CSCHED_TICKLE        TRC_SCHED_CLASS_EVT(CSCHED, 6)
 #define TRC_CSCHED_BOOST_START   TRC_SCHED_CLASS_EVT(CSCHED, 7)
 #define TRC_CSCHED_BOOST_END     TRC_SCHED_CLASS_EVT(CSCHED, 8)
+#define TRC_CSCHED_SCHEDULE      TRC_SCHED_CLASS_EVT(CSCHED, 9)
+#define TRC_CSCHED_RATELIMIT     TRC_SCHED_CLASS_EVT(CSCHED, 10)
 
 
 /*
@@ -1774,6 +1776,23 @@ csched_schedule(
     SCHED_STAT_CRANK(schedule);
     CSCHED_VCPU_CHECK(current);
 
+    /*
+     * Here in Credit1 code, we usually just call TRACE_nD() helpers, and
+     * don't care about packing. But scheduling happens very often, so it
+     * actually is important that the record is as small as possible.
+     */
+    if ( unlikely(tb_init_done) )
+    {
+        struct {
+            unsigned cpu:16, tasklet:8, idle:8;
+        } d;
+        d.cpu = cpu;
+        d.tasklet = tasklet_work_scheduled;
+        d.idle = is_idle_vcpu(current);
+        __trace_var(TRC_CSCHED_SCHEDULE, 1, sizeof(d),
+                    (unsigned char *)&d);
+    }
+
     runtime = now - current->runstate.state_entry_time;
     if ( runtime < 0 ) /* Does this ever happen? */
         runtime = 0;
@@ -1829,6 +1848,19 @@ csched_schedule(
         tslice = MICROSECS(prv->ratelimit_us) - runtime;
         if ( unlikely(runtime < CSCHED_MIN_TIMER) )
             tslice = CSCHED_MIN_TIMER;
+        if ( unlikely(tb_init_done) )
+        {
+            struct {
+                unsigned vcpu:16, dom:16;
+                unsigned runtime;
+            } d;
+            d.dom = scurr->vcpu->domain->domain_id;
+            d.vcpu = scurr->vcpu->vcpu_id;
+            d.runtime = runtime;
+            __trace_var(TRC_CSCHED_RATELIMIT, 1, sizeof(d),
+                        (unsigned char *)&d);
+        }
+
         ret.migrated = 0;
         goto out;
     }

xen/common/sched_credit2.c

@@ -55,6 +55,8 @@
 #define TRC_CSCHED2_LOAD_BALANCE     TRC_SCHED_CLASS_EVT(CSCHED2, 17)
 #define TRC_CSCHED2_PICKED_CPU       TRC_SCHED_CLASS_EVT(CSCHED2, 19)
 #define TRC_CSCHED2_RUNQ_CANDIDATE   TRC_SCHED_CLASS_EVT(CSCHED2, 20)
+#define TRC_CSCHED2_SCHEDULE         TRC_SCHED_CLASS_EVT(CSCHED2, 21)
+#define TRC_CSCHED2_RATELIMIT        TRC_SCHED_CLASS_EVT(CSCHED2, 22)
 
 /*
  * WARNING: This is still in an experimental phase.  Status and work can be found at the
@@ -2281,7 +2283,22 @@ runq_candidate(struct csched2_runqueue_data *rqd,
          vcpu_runnable(scurr->vcpu) &&
          (now - scurr->vcpu->runstate.state_entry_time) <
           MICROSECS(prv->ratelimit_us) )
+    {
+        if ( unlikely(tb_init_done) )
+        {
+            struct {
+                unsigned vcpu:16, dom:16;
+                unsigned runtime;
+            } d;
+            d.dom = scurr->vcpu->domain->domain_id;
+            d.vcpu = scurr->vcpu->vcpu_id;
+            d.runtime = now - scurr->vcpu->runstate.state_entry_time;
+            __trace_var(TRC_CSCHED2_RATELIMIT, 1,
+                        sizeof(d),
+                        (unsigned char *)&d);
+        }
         return scurr;
+    }
 
     /* Default to current if runnable, idle otherwise */
     if ( vcpu_runnable(scurr->vcpu) )
@@ -2371,6 +2388,7 @@ csched2_schedule(
     struct csched2_vcpu *snext = NULL;
     unsigned int skipped_vcpus = 0;
     struct task_slice ret;
+    bool_t tickled;
 
     SCHED_STAT_CRANK(schedule);
     CSCHED2_VCPU_CHECK(current);
@@ -2385,13 +2403,31 @@ csched2_schedule(
     BUG_ON(!is_idle_vcpu(scurr->vcpu) && scurr->rqd != rqd);
 
     /* Clear "tickled" bit now that we've been scheduled */
-    if ( cpumask_test_cpu(cpu, &rqd->tickled) )
+    tickled = cpumask_test_cpu(cpu, &rqd->tickled);
+    if ( tickled )
     {
         __cpumask_clear_cpu(cpu, &rqd->tickled);
         cpumask_andnot(cpumask_scratch, &rqd->idle, &rqd->tickled);
         smt_idle_mask_set(cpu, cpumask_scratch, &rqd->smt_idle);
     }
 
+    if ( unlikely(tb_init_done) )
+    {
+        struct {
+            unsigned cpu:16, rq_id:16;
+            unsigned tasklet:8, idle:8, smt_idle:8, tickled:8;
+        } d;
+        d.cpu = cpu;
+        d.rq_id = c2r(ops, cpu);
+        d.tasklet = tasklet_work_scheduled;
+        d.idle = is_idle_vcpu(current);
+        d.smt_idle = cpumask_test_cpu(cpu, &rqd->smt_idle);
+        d.tickled = tickled;
+        __trace_var(TRC_CSCHED2_SCHEDULE, 1,
+                    sizeof(d),
+                    (unsigned char *)&d);
+    }
+
     /* Update credits */
     burn_credits(rqd, scurr, now);
 

xen/common/sched_rt.c

@@ -160,6 +160,7 @@
 #define TRC_RTDS_BUDGET_BURN      TRC_SCHED_CLASS_EVT(RTDS, 3)
 #define TRC_RTDS_BUDGET_REPLENISH TRC_SCHED_CLASS_EVT(RTDS, 4)
 #define TRC_RTDS_SCHED_TASKLET    TRC_SCHED_CLASS_EVT(RTDS, 5)
+#define TRC_RTDS_SCHEDULE         TRC_SCHED_CLASS_EVT(RTDS, 6)
 
 static void repl_timer_handler(void *data);
 
@@ -1035,6 +1036,20 @@ rt_schedule(const struct scheduler *ops, s_time_t now, bool_t tasklet_work_sched
     struct rt_vcpu *snext = NULL;
     struct task_slice ret = { .migrated = 0 };
 
+    /* TRACE */
+    {
+        struct __packed {
+            unsigned cpu:16, tasklet:8, tickled:4, idle:4;
+        } d;
+        d.cpu = cpu;
+        d.tasklet = tasklet_work_scheduled;
+        d.tickled = cpumask_test_cpu(cpu, &prv->tickled);
+        d.idle = is_idle_vcpu(current);
+        trace_var(TRC_RTDS_SCHEDULE, 1,
+                  sizeof(d),
+                  (unsigned char *)&d);
+    }
+
     /* clear ticked bit now that we've been scheduled */
     cpumask_clear_cpu(cpu, &prv->tickled);