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.
7 // See malloc.h for an overview.
9 // The MCentral doesn't actually contain the list of free objects; the MSpan does.
10 // Each MCentral is two lists of MSpans: those with free objects (c->nonempty)
11 // and those that are completely allocated (c->empty).
13 // TODO(rsc): tcmalloc uses a "transfer cache" to split the list
14 // into sections of class_to_transfercount[sizeclass] objects
15 // so that it is faster to move those lists between MCaches and MCentrals.
21 static bool MCentral_Grow(MCentral
*c
);
22 static void MCentral_Free(MCentral
*c
, void *v
);
24 // Initialize a single central free list.
26 runtime_MCentral_Init(MCentral
*c
, int32 sizeclass
)
28 c
->sizeclass
= sizeclass
;
29 runtime_MSpanList_Init(&c
->nonempty
);
30 runtime_MSpanList_Init(&c
->empty
);
33 // Allocate up to n objects from the central free list.
34 // Return the number of objects allocated.
35 // The objects are linked together by their first words.
36 // On return, *pstart points at the first object.
38 runtime_MCentral_AllocList(MCentral
*c
, int32 n
, MLink
**pfirst
)
45 // Replenish central list if empty.
46 if(runtime_MSpanList_IsEmpty(&c
->nonempty
)) {
47 if(!MCentral_Grow(c
)) {
54 cap
= (s
->npages
<< PageShift
) / s
->elemsize
;
59 // First one is guaranteed to work, because we just grew the list.
65 s
->freelist
= last
->next
;
71 if(s
->freelist
!= nil
|| s
->ref
!= (uint32
)cap
) {
72 runtime_throw("invalid freelist");
74 runtime_MSpanList_Remove(s
);
75 runtime_MSpanList_Insert(&c
->empty
, s
);
83 // Free n objects back into the central free list.
85 runtime_MCentral_FreeList(MCentral
*c
, int32 n
, MLink
*start
)
89 // Assume next == nil marks end of list.
90 // n and end would be useful if we implemented
91 // the transfer cache optimization in the TODO above.
95 for(v
=start
; v
; v
=next
) {
102 // Helper: free one object back into the central free list.
104 MCentral_Free(MCentral
*c
, void *v
)
111 s
= runtime_MHeap_Lookup(runtime_mheap
, v
);
112 if(s
== nil
|| s
->ref
== 0)
113 runtime_throw("invalid free");
115 // Move to nonempty if necessary.
116 if(s
->freelist
== nil
) {
117 runtime_MSpanList_Remove(s
);
118 runtime_MSpanList_Insert(&c
->nonempty
, s
);
121 // Add v back to s's free list.
123 p
->next
= s
->freelist
;
127 // If s is completely freed, return it to the heap.
129 size
= runtime_class_to_size
[c
->sizeclass
];
130 runtime_MSpanList_Remove(s
);
131 runtime_unmarkspan((byte
*)(s
->start
<<PageShift
), s
->npages
<<PageShift
);
132 *(uintptr
*)(s
->start
<<PageShift
) = 1; // needs zeroing
134 c
->nfree
-= (s
->npages
<< PageShift
) / size
;
136 runtime_MHeap_Free(runtime_mheap
, s
, 0);
141 // Free n objects from a span s back into the central free list c.
144 runtime_MCentral_FreeSpan(MCentral
*c
, MSpan
*s
, int32 n
, MLink
*start
, MLink
*end
)
150 // Move to nonempty if necessary.
151 if(s
->freelist
== nil
) {
152 runtime_MSpanList_Remove(s
);
153 runtime_MSpanList_Insert(&c
->nonempty
, s
);
156 // Add the objects back to s's free list.
157 end
->next
= s
->freelist
;
162 // If s is completely freed, return it to the heap.
164 size
= runtime_class_to_size
[c
->sizeclass
];
165 runtime_MSpanList_Remove(s
);
166 *(uintptr
*)(s
->start
<<PageShift
) = 1; // needs zeroing
168 c
->nfree
-= (s
->npages
<< PageShift
) / size
;
170 runtime_unmarkspan((byte
*)(s
->start
<<PageShift
), s
->npages
<<PageShift
);
171 runtime_MHeap_Free(runtime_mheap
, s
, 0);
178 runtime_MGetSizeClassInfo(int32 sizeclass
, uintptr
*sizep
, int32
*npagesp
, int32
*nobj
)
183 npages
= runtime_class_to_allocnpages
[sizeclass
];
184 size
= runtime_class_to_size
[sizeclass
];
187 *nobj
= (npages
<< PageShift
) / size
;
190 // Fetch a new span from the heap and
191 // carve into objects for the free list.
193 MCentral_Grow(MCentral
*c
)
202 runtime_MGetSizeClassInfo(c
->sizeclass
, &size
, &npages
, &n
);
203 s
= runtime_MHeap_Alloc(runtime_mheap
, npages
, c
->sizeclass
, 0, 1);
205 // TODO(rsc): Log out of memory
210 // Carve span into sequence of blocks.
211 tailp
= &s
->freelist
;
212 p
= (byte
*)(s
->start
<< PageShift
);
213 s
->limit
= p
+ size
*n
;
221 runtime_markspan((byte
*)(s
->start
<<PageShift
), size
, n
, size
*n
< (s
->npages
<<PageShift
));
225 runtime_MSpanList_Insert(&c
->nonempty
, s
);