1 files changed, 35 insertions, 18 deletions

diff --git a/src/pkg/runtime/mgc0.c b/src/pkg/runtime/mgc0.c
index 78daa7836..e043864c1 100644
--- a/src/pkg/runtime/mgc0.c
+++ b/src/pkg/runtime/mgc0.c
@@ -52,6 +52,21 @@ enum {
 
 #define bitMask (bitBlockBoundary | bitAllocated | bitMarked | bitSpecial)
 
+// Holding worldsema grants an M the right to try to stop the world.
+// The procedure is:
+//
+//	runtime·semacquire(&runtime·worldsema);
+//	m->gcing = 1;
+//	runtime·stoptheworld();
+//
+//	... do stuff ...
+//
+//	m->gcing = 0;
+//	runtime·semrelease(&runtime·worldsema);
+//	runtime·starttheworld();
+//
+uint32 runtime·worldsema = 1;
+
 // TODO: Make these per-M.
 static uint64 nhandoff;
 
@@ -85,7 +100,7 @@ struct FinBlock
 
 extern byte data[];
 extern byte etext[];
-extern byte end[];
+extern byte ebss[];
 
 static G *fing;
 static FinBlock *finq; // list of finalizers that are to be executed
@@ -630,10 +645,7 @@ mark(void (*scan)(byte*, int64))
 	FinBlock *fb;
 
 	// mark data+bss.
-	// skip runtime·mheap itself, which has no interesting pointers
-	// and is mostly zeroed and would not otherwise be paged in.
-	scan(data, (byte*)&runtime·mheap - data);
-	scan((byte*)(&runtime·mheap+1), end - (byte*)(&runtime·mheap+1));
+	scan(data, ebss - data);
 
 	// mark stacks
 	for(gp=runtime·allg; gp!=nil; gp=gp->alllink) {
@@ -716,8 +728,10 @@ sweep(void)
 	byte *p;
 	MCache *c;
 	byte *arena_start;
+	int64 now;
 
 	arena_start = runtime·mheap.arena_start;
+	now = runtime·nanotime();
 
 	for(;;) {
 		s = work.spans;
@@ -726,6 +740,11 @@ sweep(void)
 		if(!runtime·casp(&work.spans, s, s->allnext))
 			continue;
 
+		// Stamp newly unused spans. The scavenger will use that
+		// info to potentially give back some pages to the OS.
+		if(s->state == MSpanFree && s->unusedsince == 0)
+			s->unusedsince = now;
+
 		if(s->state != MSpanInUse)
 			continue;
 
@@ -812,11 +831,6 @@ runtime·gchelper(void)
 		runtime·notewakeup(&work.alldone);
 }
 
-// Semaphore, not Lock, so that the goroutine
-// reschedules when there is contention rather
-// than spinning.
-static uint32 gcsema = 1;
-
 // Initialized from $GOGC.  GOGC=off means no gc.
 //
 // Next gc is after we've allocated an extra amount of
@@ -899,9 +913,9 @@ runtime·gc(int32 force)
 	if(gcpercent < 0)
 		return;
 
-	runtime·semacquire(&gcsema);
+	runtime·semacquire(&runtime·worldsema);
 	if(!force && mstats.heap_alloc < mstats.next_gc) {
-		runtime·semrelease(&gcsema);
+		runtime·semrelease(&runtime·worldsema);
 		return;
 	}
 
@@ -963,6 +977,7 @@ runtime·gc(int32 force)
 	obj1 = mstats.nmalloc - mstats.nfree;
 
 	t3 = runtime·nanotime();
+	mstats.last_gc = t3;
 	mstats.pause_ns[mstats.numgc%nelem(mstats.pause_ns)] = t3 - t0;
 	mstats.pause_total_ns += t3 - t0;
 	mstats.numgc++;
@@ -976,8 +991,9 @@ runtime·gc(int32 force)
 			mstats.nmalloc, mstats.nfree,
 			nhandoff);
 	}
-
-	runtime·semrelease(&gcsema);
+	
+	runtime·MProf_GC();
+	runtime·semrelease(&runtime·worldsema);
 
 	// If we could have used another helper proc, start one now,
 	// in the hope that it will be available next time.
@@ -997,18 +1013,19 @@ runtime·gc(int32 force)
 }
 
 void
-runtime·UpdateMemStats(void)
+runtime·ReadMemStats(MStats *stats)
 {
-	// Have to acquire gcsema to stop the world,
+	// Have to acquire worldsema to stop the world,
 	// because stoptheworld can only be used by
 	// one goroutine at a time, and there might be
 	// a pending garbage collection already calling it.
-	runtime·semacquire(&gcsema);
+	runtime·semacquire(&runtime·worldsema);
 	m->gcing = 1;
 	runtime·stoptheworld();
 	cachestats();
+	*stats = mstats;
 	m->gcing = 0;
-	runtime·semrelease(&gcsema);
+	runtime·semrelease(&runtime·worldsema);
 	runtime·starttheworld(false);
 }