1 files changed, 131 insertions, 0 deletions
diff --git a/libgo/runtime/mcache.c b/libgo/runtime/mcache.c
new file mode 100644
index 000000000..ce6575758
--- /dev/null
+++ b/libgo/runtime/mcache.c
@@ -0,0 +1,131 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Per-thread (in Go, per-M) malloc cache for small objects.
+//
+// See malloc.h for an overview.
+
+#include "runtime.h"
+#include "malloc.h"
+
+void*
+runtime_MCache_Alloc(MCache *c, int32 sizeclass, uintptr size, int32 zeroed)
+{
+	MCacheList *l;
+	MLink *first, *v;
+	int32 n;
+
+	// Allocate from list.
+	l = &c->list[sizeclass];
+	if(l->list == nil) {
+		// Replenish using central lists.
+		n = runtime_MCentral_AllocList(&runtime_mheap.central[sizeclass],
+			runtime_class_to_transfercount[sizeclass], &first);
+		l->list = first;
+		l->nlist = n;
+		c->size += n*size;
+	}
+	v = l->list;
+	l->list = v->next;
+	l->nlist--;
+	if(l->nlist < l->nlistmin)
+		l->nlistmin = l->nlist;
+	c->size -= size;
+
+	// v is zeroed except for the link pointer
+	// that we used above; zero that.
+	v->next = nil;
+	if(zeroed) {
+		// block is zeroed iff second word is zero ...
+		if(size > sizeof(uintptr) && ((uintptr*)v)[1] != 0)
+			runtime_memclr((byte*)v, size);
+		else {
+			// ... except for the link pointer
+			// that we used above; zero that.
+			v->next = nil;
+		}
+	}
+	c->local_alloc += size;
+	c->local_objects++;
+	return v;
+}
+
+// Take n elements off l and return them to the central free list.
+static void
+ReleaseN(MCache *c, MCacheList *l, int32 n, int32 sizeclass)
+{
+	MLink *first, **lp;
+	int32 i;
+
+	// Cut off first n elements.
+	first = l->list;
+	lp = &l->list;
+	for(i=0; i<n; i++)
+		lp = &(*lp)->next;
+	l->list = *lp;
+	*lp = nil;
+	l->nlist -= n;
+	if(l->nlist < l->nlistmin)
+		l->nlistmin = l->nlist;
+	c->size -= n*runtime_class_to_size[sizeclass];
+
+	// Return them to central free list.
+	runtime_MCentral_FreeList(&runtime_mheap.central[sizeclass], n, first);
+}
+
+void
+runtime_MCache_Free(MCache *c, void *v, int32 sizeclass, uintptr size)
+{
+	int32 i, n;
+	MCacheList *l;
+	MLink *p;
+
+	// Put back on list.
+	l = &c->list[sizeclass];
+	p = v;
+	p->next = l->list;
+	l->list = p;
+	l->nlist++;
+	c->size += size;
+	c->local_alloc -= size;
+	c->local_objects--;
+
+	if(l->nlist >= MaxMCacheListLen) {
+		// Release a chunk back.
+		ReleaseN(c, l, runtime_class_to_transfercount[sizeclass], sizeclass);
+	}
+
+	if(c->size >= MaxMCacheSize) {
+		// Scavenge.
+		for(i=0; i<NumSizeClasses; i++) {
+			l = &c->list[i];
+			n = l->nlistmin;
+
+			// n is the minimum number of elements we've seen on
+			// the list since the last scavenge.  If n > 0, it means that
+			// we could have gotten by with n fewer elements
+			// without needing to consult the central free list.
+			// Move toward that situation by releasing n/2 of them.
+			if(n > 0) {
+				if(n > 1)
+					n /= 2;
+				ReleaseN(c, l, n, i);
+			}
+			l->nlistmin = l->nlist;
+		}
+	}
+}
+
+void
+runtime_MCache_ReleaseAll(MCache *c)
+{
+	int32 i;
+	MCacheList *l;
+
+	for(i=0; i<NumSizeClasses; i++) {
+		l = &c->list[i];
+		ReleaseN(c, l, l->nlist, i);
+		l->nlistmin = 0;
+	}
+}