[Qemu-devel] [PATCH 2/2] trace: track enabled events in a separate array

[Paolo Bonzini <pbonzini@redhat.com>]

This is more cache friendly on the fast path, where we already have
the event id available.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 scripts/tracetool/format/events_c.py |  2 +-
 trace/control-internal.h             | 15 +++++++++++----
 trace/control.c                      |  1 +
 trace/control.h                      |  2 +-
 trace/event-internal.h               |  2 --
 5 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/scripts/tracetool/format/events_c.py b/scripts/tracetool/format/events_c.py
index 2d97fa3..2717ea3 100644
--- a/scripts/tracetool/format/events_c.py
+++ b/scripts/tracetool/format/events_c.py
@@ -27,7 +27,7 @@ def generate(events, backend):
     out('TraceEvent trace_events[TRACE_EVENT_COUNT] = {')
 
     for e in events:
-        out('    { .id = %(id)s, .name = \"%(name)s\", .sstate = %(sstate)s, .dstate = 0 },',
+        out('    { .id = %(id)s, .name = \"%(name)s\", .sstate = %(sstate)s },',
             id = "TRACE_" + e.name.upper(),
             name = e.name,
             sstate = "TRACE_%s_ENABLED" % e.name.upper())
diff --git a/trace/control-internal.h b/trace/control-internal.h
index 271bddb..07cb1c1 100644
--- a/trace/control-internal.h
+++ b/trace/control-internal.h
@@ -14,6 +14,7 @@
 
 
 extern TraceEvent trace_events[];
+extern bool trace_events_dstate[];
 extern int trace_events_enabled_count;
 
 
@@ -52,18 +53,24 @@ static inline bool trace_event_get_state_static(TraceEvent *ev)
     return ev->sstate;
 }
 
+static inline bool trace_event_get_state_dynamic_by_id(int id)
+{
+    return unlikely(trace_events_enabled_count) && trace_events_dstate[id];
+}
+
 static inline bool trace_event_get_state_dynamic(TraceEvent *ev)
 {
-    assert(ev != NULL);
-    return unlikely(trace_events_enabled_count) && ev->dstate;
+    int id = trace_event_get_id(ev);
+    return trace_event_get_state_dynamic_by_id(id);
 }
 
 static inline void trace_event_set_state_dynamic(TraceEvent *ev, bool state)
 {
+    int id = trace_event_get_id(ev);
     assert(ev != NULL);
     assert(trace_event_get_state_static(ev));
-    trace_events_enabled_count += state - ev->dstate;
-    ev->dstate = state;
+    trace_events_enabled_count += state - trace_events_dstate[id];
+    trace_events_dstate[id] = state;
 }
 
 #endif  /* TRACE__CONTROL_INTERNAL_H */
diff --git a/trace/control.c b/trace/control.c
index 95fbc07..700440c 100644
--- a/trace/control.c
+++ b/trace/control.c
@@ -17,6 +17,7 @@
 #include "qemu/error-report.h"
 
 int trace_events_enabled_count;
+bool trace_events_dstate[TRACE_EVENT_COUNT];
 
 TraceEvent *trace_event_name(const char *name)
 {
diff --git a/trace/control.h b/trace/control.h
index da9bb6b..6af7ddc 100644
--- a/trace/control.h
+++ b/trace/control.h
@@ -104,7 +104,7 @@ static const char * trace_event_get_name(TraceEvent *ev);
  * As a down side, you must always use an immediate #TraceEventID value.
  */
 #define trace_event_get_state(id)                       \
-    ((id ##_ENABLED) && trace_event_get_state_dynamic(trace_event_id(id)))
+    ((id ##_ENABLED) && trace_event_get_state_dynamic_by_id(id))
 
 /**
  * trace_event_get_state_static:
diff --git a/trace/event-internal.h b/trace/event-internal.h
index b2310d9..86f6a51 100644
--- a/trace/event-internal.h
+++ b/trace/event-internal.h
@@ -18,7 +18,6 @@
  * @id: Unique event identifier.
  * @name: Event name.
  * @sstate: Static tracing state.
- * @dstate: Dynamic tracing state.
  *
  * Opaque generic description of a tracing event.
  */
@@ -26,7 +25,6 @@ typedef struct TraceEvent {
     TraceEventID id;
     const char * name;
     const bool sstate;
-    bool dstate;
 } TraceEvent;
 
 
-- 
2.5.0