trace: remove global 'uint16 dstate[]' array

Instead of having a global dstate array, declare a single
'uint16 TRACE_${EVENT_NAME}_DSTATE' variable for each
trace event. Record a pointer to this variable in the
TraceEvent struct too.

By turning trace_event_get_state_dynamic_by_id into a
macro, this still hits the fast path, and cache affinity
is ensured by declaring all the uint16 vars adjacent to
each other.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Lluís Vilanova <vilanova@ac.upc.edu>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 1475588159-30598-7-git-send-email-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

4 files changed, 21 insertions, 31 deletions

diff --git a/trace/control-internal.h b/trace/control-internal.h
index 7f31e39059..a6d8d2e7c9 100644
--- a/trace/control-internal.h
+++ b/trace/control-internal.h
@@ -16,7 +16,6 @@
 
 
 extern TraceEvent trace_events[];
-extern uint16_t trace_events_dstate[];
 extern int trace_events_enabled_count;
 
 
@@ -54,18 +53,13 @@ static inline bool trace_event_get_state_static(TraceEvent *ev)
     return ev->sstate;
 }
 
-static inline bool trace_event_get_state_dynamic_by_id(TraceEventID id)
-{
-    /* it's on fast path, avoid consistency checks (asserts) */
-    return unlikely(trace_events_enabled_count) && trace_events_dstate[id];
-}
+/* it's on fast path, avoid consistency checks (asserts) */
+#define trace_event_get_state_dynamic_by_id(id) \
+    (unlikely(trace_events_enabled_count) && _ ## id ## _DSTATE)
 
 static inline bool trace_event_get_state_dynamic(TraceEvent *ev)
 {
-    TraceEventID id;
-    assert(trace_event_get_state_static(ev));
-    id = trace_event_get_id(ev);
-    return trace_event_get_state_dynamic_by_id(id);
+    return unlikely(trace_events_enabled_count) && *ev->dstate;
 }
 
 static inline bool trace_event_get_vcpu_state_dynamic_by_vcpu_id(CPUState *vcpu,
diff --git a/trace/control-target.c b/trace/control-target.c
index 50bac4fb7d..3b55941414 100644
--- a/trace/control-target.c
+++ b/trace/control-target.c
@@ -16,21 +16,20 @@
 
 void trace_event_set_state_dynamic_init(TraceEvent *ev, bool state)
 {
-    TraceEventID id = trace_event_get_id(ev);
     bool state_pre;
     assert(trace_event_get_state_static(ev));
     /*
      * We ignore the "vcpu" property here, since no vCPUs have been created
      * yet. Then dstate can only be 1 or 0.
      */
-    state_pre = trace_events_dstate[id];
+    state_pre = *ev->dstate;
     if (state_pre != state) {
         if (state) {
             trace_events_enabled_count++;
-            trace_events_dstate[id] = 1;
+            *ev->dstate = 1;
         } else {
             trace_events_enabled_count--;
-            trace_events_dstate[id] = 0;
+            *ev->dstate = 0;
         }
     }
 }
@@ -45,15 +44,14 @@ void trace_event_set_state_dynamic(TraceEvent *ev, bool state)
         }
     } else {
         /* Without the "vcpu" property, dstate can only be 1 or 0 */
-        TraceEventID id = trace_event_get_id(ev);
-        bool state_pre = trace_events_dstate[id];
+        bool state_pre = *ev->dstate;
         if (state_pre != state) {
             if (state) {
                 trace_events_enabled_count++;
-                trace_events_dstate[id] = 1;
+                *ev->dstate = 1;
             } else {
                 trace_events_enabled_count--;
-                trace_events_dstate[id] = 0;
+                *ev->dstate = 0;
             }
         }
     }
@@ -62,23 +60,21 @@ void trace_event_set_state_dynamic(TraceEvent *ev, bool state)
 void trace_event_set_vcpu_state_dynamic(CPUState *vcpu,
                                         TraceEvent *ev, bool state)
 {
-    TraceEventID id;
     TraceEventVCPUID vcpu_id;
     bool state_pre;
     assert(trace_event_get_state_static(ev));
     assert(trace_event_is_vcpu(ev));
-    id = trace_event_get_id(ev);
     vcpu_id = trace_event_get_vcpu_id(ev);
     state_pre = test_bit(vcpu_id, vcpu->trace_dstate);
     if (state_pre != state) {
         if (state) {
             trace_events_enabled_count++;
             set_bit(vcpu_id, vcpu->trace_dstate);
-            trace_events_dstate[id]++;
+            (*ev->dstate)++;
         } else {
             trace_events_enabled_count--;
             clear_bit(vcpu_id, vcpu->trace_dstate);
-            trace_events_dstate[id]--;
+            (*ev->dstate)--;
         }
     }
 }
@@ -105,12 +101,11 @@ void trace_init_vcpu(CPUState *vcpu)
         if (trace_event_is_vcpu(ev) &&
             trace_event_get_state_static(ev) &&
             trace_event_get_state_dynamic(ev)) {
-            TraceEventID id = trace_event_get_id(ev);
             if (adding_first_cpu()) {
                 /* check preconditions */
-                assert(trace_events_dstate[id] == 1);
+                assert(*ev->dstate == 1);
                 /* disable early-init state ... */
-                trace_events_dstate[id] = 0;
+                *ev->dstate = 0;
                 trace_events_enabled_count--;
                 /* ... and properly re-enable */
                 trace_event_set_vcpu_state_dynamic(vcpu, ev, true);
diff --git a/trace/control.c b/trace/control.c
index a423f32eb0..e57f2d3f05 100644
--- a/trace/control.c
+++ b/trace/control.c
@@ -28,12 +28,6 @@
 #include "monitor/monitor.h"
 
 int trace_events_enabled_count;
-/*
- * Interpretation depends on wether the event has the 'vcpu' property:
- * - false: Boolean value indicating whether the event is active.
- * - true : Integral counting the number of vCPUs that have this event enabled.
- */
-uint16_t trace_events_dstate[TRACE_EVENT_COUNT];
 
 QemuOptsList qemu_trace_opts = {
     .name = "trace",
diff --git a/trace/event-internal.h b/trace/event-internal.h
index 074faf6862..4a98d09153 100644
--- a/trace/event-internal.h
+++ b/trace/event-internal.h
@@ -19,6 +19,12 @@
  * @vcpu_id: Unique per-vCPU event identifier.
  * @name: Event name.
  * @sstate: Static tracing state.
+ * @dstate: Dynamic tracing state
+ *
+ * Interpretation of @dstate depends on whether the event has the 'vcpu'
+ *  property:
+ * - false: Boolean value indicating whether the event is active.
+ * - true : Integral counting the number of vCPUs that have this event enabled.
  *
  * Opaque generic description of a tracing event.
  */
@@ -27,6 +33,7 @@ typedef struct TraceEvent {
     TraceEventVCPUID vcpu_id;
     const char * name;
     const bool sstate;
+    uint16_t *dstate;
 } TraceEvent;
 
 void trace_event_set_state_dynamic_init(TraceEvent *ev, bool state);