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.
14 runtime_MCache_Alloc(MCache
*c
, int32 sizeclass
, uintptr size
, int32 zeroed
)
20 // Allocate from list.
21 l
= &c
->list
[sizeclass
];
23 // Replenish using central lists.
24 n
= runtime_MCentral_AllocList(&runtime_mheap
.central
[sizeclass
],
25 runtime_class_to_transfercount
[sizeclass
], &first
);
27 runtime_throw("out of memory");
35 if(l
->nlist
< l
->nlistmin
)
36 l
->nlistmin
= l
->nlist
;
39 // v is zeroed except for the link pointer
40 // that we used above; zero that.
43 // block is zeroed iff second word is zero ...
44 if(size
> sizeof(uintptr
) && ((uintptr
*)v
)[1] != 0)
45 runtime_memclr((byte
*)v
, size
);
47 // ... except for the link pointer
48 // that we used above; zero that.
52 c
->local_cachealloc
+= size
;
57 // Take n elements off l and return them to the central free list.
59 ReleaseN(MCache
*c
, MCacheList
*l
, int32 n
, int32 sizeclass
)
64 // Cut off first n elements.
72 if(l
->nlist
< l
->nlistmin
)
73 l
->nlistmin
= l
->nlist
;
74 c
->size
-= n
*runtime_class_to_size
[sizeclass
];
76 // Return them to central free list.
77 runtime_MCentral_FreeList(&runtime_mheap
.central
[sizeclass
], n
, first
);
81 runtime_MCache_Free(MCache
*c
, void *v
, int32 sizeclass
, uintptr size
)
88 l
= &c
->list
[sizeclass
];
94 c
->local_cachealloc
-= size
;
97 if(l
->nlist
>= MaxMCacheListLen
) {
98 // Release a chunk back.
99 ReleaseN(c
, l
, runtime_class_to_transfercount
[sizeclass
], sizeclass
);
102 if(c
->size
>= MaxMCacheSize
) {
104 for(i
=0; i
<NumSizeClasses
; i
++) {
108 // n is the minimum number of elements we've seen on
109 // the list since the last scavenge. If n > 0, it means that
110 // we could have gotten by with n fewer elements
111 // without needing to consult the central free list.
112 // Move toward that situation by releasing n/2 of them.
116 ReleaseN(c
, l
, n
, i
);
118 l
->nlistmin
= l
->nlist
;
124 runtime_MCache_ReleaseAll(MCache
*c
)
129 for(i
=0; i
<NumSizeClasses
; i
++) {
131 ReleaseN(c
, l
, l
->nlist
, i
);