1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
5 // Per-thread (in Go, per-M) malloc cache for small objects.
7 // See malloc.h for an overview.
13 runtime_MCache_Alloc(MCache *c, int32 sizeclass, uintptr size, int32 zeroed)
19 // Allocate from list.
20 l = &c->list[sizeclass];
22 // Replenish using central lists.
23 n = runtime_MCentral_AllocList(&runtime_mheap.central[sizeclass],
24 runtime_class_to_transfercount[sizeclass], &first);
32 if(l->nlist < l->nlistmin)
33 l->nlistmin = l->nlist;
36 // v is zeroed except for the link pointer
37 // that we used above; zero that.
40 // block is zeroed iff second word is zero ...
41 if(size > sizeof(uintptr) && ((uintptr*)v)[1] != 0)
42 runtime_memclr((byte*)v, size);
44 // ... except for the link pointer
45 // that we used above; zero that.
49 c->local_alloc += size;
54 // Take n elements off l and return them to the central free list.
56 ReleaseN(MCache *c, MCacheList *l, int32 n, int32 sizeclass)
61 // Cut off first n elements.
69 if(l->nlist < l->nlistmin)
70 l->nlistmin = l->nlist;
71 c->size -= n*runtime_class_to_size[sizeclass];
73 // Return them to central free list.
74 runtime_MCentral_FreeList(&runtime_mheap.central[sizeclass], n, first);
78 runtime_MCache_Free(MCache *c, void *v, int32 sizeclass, uintptr size)
85 l = &c->list[sizeclass];
91 c->local_alloc -= size;
94 if(l->nlist >= MaxMCacheListLen) {
95 // Release a chunk back.
96 ReleaseN(c, l, runtime_class_to_transfercount[sizeclass], sizeclass);
99 if(c->size >= MaxMCacheSize) {
101 for(i=0; i<NumSizeClasses; i++) {
105 // n is the minimum number of elements we've seen on
106 // the list since the last scavenge. If n > 0, it means that
107 // we could have gotten by with n fewer elements
108 // without needing to consult the central free list.
109 // Move toward that situation by releasing n/2 of them.
113 ReleaseN(c, l, n, i);
115 l->nlistmin = l->nlist;
121 runtime_MCache_ReleaseAll(MCache *c)
126 for(i=0; i<NumSizeClasses; i++) {
128 ReleaseN(c, l, l->nlist, i);