diff -r c8d973732b42 libgo/runtime/malloc.goc
--- a/libgo/runtime/malloc.goc	Thu Apr 19 21:46:43 2012 -0700
+++ b/libgo/runtime/malloc.goc	Thu Apr 19 21:50:27 2012 -0700
@@ -72,7 +72,7 @@
 		npages = size >> PageShift;
 		if((size & PageMask) != 0)
 			npages++;
-		s = runtime_MHeap_Alloc(&runtime_mheap, npages, 0, !(flag & FlagNoGC));
+		s = runtime_MHeap_Alloc(&runtime_mheap, npages, 0, 1);
 		if(s == nil)
 			runtime_throw("out of memory");
 		size = npages<<PageShift;
diff -r c8d973732b42 libgo/runtime/mgc0.c
--- a/libgo/runtime/mgc0.c	Thu Apr 19 21:46:43 2012 -0700
+++ b/libgo/runtime/mgc0.c	Thu Apr 19 21:50:27 2012 -0700
@@ -4,6 +4,8 @@
 
 // Garbage collector.
 
+#include <unistd.h>
+
 #include "runtime.h"
 #include "arch.h"
 #include "malloc.h"
@@ -918,7 +920,7 @@
 	uint64 stacks_sys;
 
 	stacks_inuse = 0;
-	stacks_sys = 0;
+	stacks_sys = runtime_stacks_sys;
 	for(m=runtime_allm; m; m=m->alllink) {
 		runtime_purgecachedstats(m);
 		// stacks_inuse += m->stackalloc->inuse;
@@ -1020,7 +1022,7 @@
 	stealcache();
 	cachestats();
 
-	mstats.next_gc = mstats.heap_alloc+mstats.heap_alloc*gcpercent/100;
+	mstats.next_gc = mstats.heap_alloc+(mstats.heap_alloc-runtime_stacks_sys)*gcpercent/100;
 	m->gcing = 0;
 
 	m->locks++;	// disable gc during the mallocs in newproc
@@ -1329,6 +1331,8 @@
 void
 runtime_MHeap_MapBits(MHeap *h)
 {
+	size_t page_size;
+
 	// Caller has added extra mappings to the arena.
 	// Add extra mappings of bitmap words as needed.
 	// We allocate extra bitmap pieces in chunks of bitmapChunk.
@@ -1342,6 +1346,9 @@
 	if(h->bitmap_mapped >= n)
 		return;
 
+	page_size = getpagesize();
+	n = (n+page_size-1) & ~(page_size-1);
+
 	runtime_SysMap(h->arena_start - n, n - h->bitmap_mapped);
 	h->bitmap_mapped = n;
 }
diff -r c8d973732b42 libgo/runtime/proc.c
--- a/libgo/runtime/proc.c	Thu Apr 19 21:46:43 2012 -0700
+++ b/libgo/runtime/proc.c	Thu Apr 19 21:50:27 2012 -0700
@@ -46,6 +46,8 @@
 # define StackMin 2 * 1024 * 1024
 #endif
 
+uintptr runtime_stacks_sys;
+
 static void schedule(G*);
 
 typedef struct Sched Sched;
@@ -1091,6 +1093,7 @@
 				m->lockedg = nil;
 			}
 			gp->idlem = nil;
+			runtime_memclr(&gp->context, sizeof gp->context);
 			gfput(gp);
 			if(--runtime_sched.gcount == 0)
 				runtime_exit(0);
@@ -1288,6 +1291,7 @@
 		*ret_stacksize = stacksize;
 		newg->gcinitial_sp = *ret_stack;
 		newg->gcstack_size = stacksize;
+		runtime_xadd(&runtime_stacks_sys, stacksize);
 #endif
 	}
 	return newg;
diff -r c8d973732b42 libgo/runtime/runtime.h
--- a/libgo/runtime/runtime.h	Thu Apr 19 21:46:43 2012 -0700
+++ b/libgo/runtime/runtime.h	Thu Apr 19 21:50:27 2012 -0700
@@ -463,3 +463,8 @@
 };
 
 void	__go_register_gc_roots(struct root_list*);
+
+// Size of stack space allocated using Go's allocator.
+// This will be 0 when using split stacks, as in that case
+// the stacks are allocated by the splitstack library.
+extern uintptr runtime_stacks_sys;