Fix the timestamps in GC_START and GC_END events on the GC-initiating cap

There was a discrepancy between GC times reported in +RTS -s
and the timestamps of GC_START and GC_END events on the cap,
on which +RTS -s stats for the given GC are based.
This is fixed by posting the events with exactly the same timestamp
as generated for the stat calculation. The calls posting the events
are moved too, so that the events are emitted close to the time instant
they claim to be emitted at. The GC_STATS_GHC was moved, too, ensuring
it's emitted before the moved GC_END on all caps, which simplifies tools code.

2 files changed, 23 insertions, 1 deletions

diff --git a/rts/eventlog/EventLog.c b/rts/eventlog/EventLog.c
index 8e7cf3784d..aab93bbd92 100644
--- a/rts/eventlog/EventLog.c
+++ b/rts/eventlog/EventLog.c
@@ -839,7 +839,7 @@ void postHeapEvent (Capability    *cap,
     case EVENT_HEAP_LIVE:          // (heap_capset, live_bytes)
     {
         postCapsetID(eb, heap_capset);
-        postWord64(eb,info1 /* alloc/size/live_bytes */);
+        postWord64(eb, info1 /* alloc/size/live_bytes */);
         break;
     }
 
@@ -924,6 +924,25 @@ postEvent (Capability *cap, EventTypeNum tag)
     postEventHeader(eb, tag);
 }
 
+void
+postEventAtTimestamp (Capability *cap, EventTimestamp ts, EventTypeNum tag)
+{
+    EventsBuf *eb;
+
+    eb = &capEventBuf[cap->no];
+
+    if (!hasRoomForEvent(eb, tag)) {
+        // Flush event buffer to make room for new event.
+        printAndClearEventBuf(eb);
+    }
+
+    /* Normally we'd call postEventHeader(), but that generates its own
+       timestamp, so we go one level lower so we can write out
+       the timestamp we received as an argument. */
+    postEventTypeNum(eb, tag);
+    postWord64(eb, ts);
+}
+
 #define BUF 512
 
 void postLogMsg(EventsBuf *eb, EventTypeNum type, char *msg, va_list ap)
diff --git a/rts/eventlog/EventLog.h b/rts/eventlog/EventLog.h
index dadc6fa6d9..d1b0814114 100644
--- a/rts/eventlog/EventLog.h
+++ b/rts/eventlog/EventLog.h
@@ -40,6 +40,9 @@ void postSchedEvent(Capability *cap, EventTypeNum tag,
  */
 void postEvent(Capability *cap, EventTypeNum tag);
 
+void postEventAtTimestamp (Capability *cap, EventTimestamp ts, 
+                           EventTypeNum tag);
+
 void postMsg(char *msg, va_list ap);
 
 void postUserMsg(Capability *cap, char *msg, va_list ap);