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 overview.
9 // When a MSpan is in the heap free list, state == MSpanFree
10 // and heapmap(s->start) == span, heapmap(s->start+s->npages-1) == span.
12 // When a MSpan is allocated, state == MSpanInUse
13 // and heapmap(i) == span for all s->start <= i < s->start+s->npages.
19 static MSpan *MHeap_AllocLocked(MHeap*, uintptr, int32);
20 static bool MHeap_Grow(MHeap*, uintptr);
21 static void MHeap_FreeLocked(MHeap*, MSpan*);
22 static MSpan *MHeap_AllocLarge(MHeap*, uintptr);
23 static MSpan *BestFit(MSpan*, uintptr, MSpan*);
26 RecordSpan(void *vh, byte *p)
33 s->allnext = h->allspans;
37 // Initialize the heap; fetch memory using alloc.
39 runtime_MHeap_Init(MHeap *h, void *(*alloc)(uintptr))
43 runtime_FixAlloc_Init(&h->spanalloc, sizeof(MSpan), alloc, RecordSpan, h);
44 runtime_FixAlloc_Init(&h->cachealloc, sizeof(MCache), alloc, nil, nil);
45 // h->mapcache needs no init
46 for(i=0; i<nelem(h->free); i++)
47 runtime_MSpanList_Init(&h->free[i]);
48 runtime_MSpanList_Init(&h->large);
49 for(i=0; i<nelem(h->central); i++)
50 runtime_MCentral_Init(&h->central[i], i);
53 // Allocate a new span of npage pages from the heap
54 // and record its size class in the HeapMap and HeapMapCache.
56 runtime_MHeap_Alloc(MHeap *h, uintptr npage, int32 sizeclass, int32 acct)
61 runtime_purgecachedstats(runtime_m());
62 s = MHeap_AllocLocked(h, npage, sizeclass);
64 mstats.heap_inuse += npage<<PageShift;
66 mstats.heap_objects++;
67 mstats.heap_alloc += npage<<PageShift;
75 MHeap_AllocLocked(MHeap *h, uintptr npage, int32 sizeclass)
81 // Try in fixed-size lists up to max.
82 for(n=npage; n < nelem(h->free); n++) {
83 if(!runtime_MSpanList_IsEmpty(&h->free[n])) {
89 // Best fit in list of large spans.
90 if((s = MHeap_AllocLarge(h, npage)) == nil) {
91 if(!MHeap_Grow(h, npage))
93 if((s = MHeap_AllocLarge(h, npage)) == nil)
99 if(s->state != MSpanFree)
100 runtime_throw("MHeap_AllocLocked - MSpan not free");
101 if(s->npages < npage)
102 runtime_throw("MHeap_AllocLocked - bad npages");
103 runtime_MSpanList_Remove(s);
104 s->state = MSpanInUse;
105 mstats.heap_idle -= s->npages<<PageShift;
107 if(s->npages > npage) {
108 // Trim extra and put it back in the heap.
109 t = runtime_FixAlloc_Alloc(&h->spanalloc);
110 mstats.mspan_inuse = h->spanalloc.inuse;
111 mstats.mspan_sys = h->spanalloc.sys;
112 runtime_MSpan_Init(t, s->start + npage, s->npages - npage);
115 if(sizeof(void*) == 8)
116 p -= ((uintptr)h->arena_start>>PageShift);
120 h->map[p+t->npages-1] = t;
121 *(uintptr*)(t->start<<PageShift) = *(uintptr*)(s->start<<PageShift); // copy "needs zeroing" mark
122 t->state = MSpanInUse;
123 MHeap_FreeLocked(h, t);
126 if(*(uintptr*)(s->start<<PageShift) != 0)
127 runtime_memclr((byte*)(s->start<<PageShift), s->npages<<PageShift);
129 // Record span info, because gc needs to be
130 // able to map interior pointer to containing span.
131 s->sizeclass = sizeclass;
133 if(sizeof(void*) == 8)
134 p -= ((uintptr)h->arena_start>>PageShift);
135 for(n=0; n<npage; n++)
140 // Allocate a span of exactly npage pages from the list of large spans.
142 MHeap_AllocLarge(MHeap *h, uintptr npage)
144 return BestFit(&h->large, npage, nil);
147 // Search list for smallest span with >= npage pages.
148 // If there are multiple smallest spans, take the one
149 // with the earliest starting address.
151 BestFit(MSpan *list, uintptr npage, MSpan *best)
155 for(s=list->next; s != list; s=s->next) {
156 if(s->npages < npage)
159 || s->npages < best->npages
160 || (s->npages == best->npages && s->start < best->start))
166 // Try to add at least npage pages of memory to the heap,
167 // returning whether it worked.
169 MHeap_Grow(MHeap *h, uintptr npage)
176 // Ask for a big chunk, to reduce the number of mappings
177 // the operating system needs to track; also amortizes
178 // the overhead of an operating system mapping.
179 // Allocate a multiple of 64kB (16 pages).
180 npage = (npage+15)&~15;
181 ask = npage<<PageShift;
182 if(ask < HeapAllocChunk)
183 ask = HeapAllocChunk;
185 v = runtime_MHeap_SysAlloc(h, ask);
187 if(ask > (npage<<PageShift)) {
188 ask = npage<<PageShift;
189 v = runtime_MHeap_SysAlloc(h, ask);
192 runtime_printf("runtime: out of memory: cannot allocate %llu-byte block (%llu in use)\n", (unsigned long long)ask, (unsigned long long)mstats.heap_sys);
196 mstats.heap_sys += ask;
198 // Create a fake "in use" span and free it, so that the
199 // right coalescing happens.
200 s = runtime_FixAlloc_Alloc(&h->spanalloc);
201 mstats.mspan_inuse = h->spanalloc.inuse;
202 mstats.mspan_sys = h->spanalloc.sys;
203 runtime_MSpan_Init(s, (uintptr)v>>PageShift, ask>>PageShift);
205 if(sizeof(void*) == 8)
206 p -= ((uintptr)h->arena_start>>PageShift);
208 h->map[p + s->npages - 1] = s;
209 s->state = MSpanInUse;
210 MHeap_FreeLocked(h, s);
214 // Look up the span at the given address.
215 // Address is guaranteed to be in map
216 // and is guaranteed to be start or end of span.
218 runtime_MHeap_Lookup(MHeap *h, void *v)
223 if(sizeof(void*) == 8)
224 p -= (uintptr)h->arena_start;
225 return h->map[p >> PageShift];
228 // Look up the span at the given address.
229 // Address is *not* guaranteed to be in map
230 // and may be anywhere in the span.
231 // Map entries for the middle of a span are only
232 // valid for allocated spans. Free spans may have
233 // other garbage in their middles, so we have to
236 runtime_MHeap_LookupMaybe(MHeap *h, void *v)
241 if((byte*)v < h->arena_start || (byte*)v >= h->arena_used)
243 p = (uintptr)v>>PageShift;
245 if(sizeof(void*) == 8)
246 q -= (uintptr)h->arena_start >> PageShift;
248 if(s == nil || p < s->start || p - s->start >= s->npages)
250 if(s->state != MSpanInUse)
255 // Free the span back into the heap.
257 runtime_MHeap_Free(MHeap *h, MSpan *s, int32 acct)
260 runtime_purgecachedstats(runtime_m());
261 mstats.heap_inuse -= s->npages<<PageShift;
263 mstats.heap_alloc -= s->npages<<PageShift;
264 mstats.heap_objects--;
266 MHeap_FreeLocked(h, s);
271 MHeap_FreeLocked(MHeap *h, MSpan *s)
277 if(s->state != MSpanInUse || s->ref != 0) {
278 // runtime_printf("MHeap_FreeLocked - span %p ptr %p state %d ref %d\n", s, s->start<<PageShift, s->state, s->ref);
279 runtime_throw("MHeap_FreeLocked - invalid free");
281 mstats.heap_idle += s->npages<<PageShift;
282 s->state = MSpanFree;
283 runtime_MSpanList_Remove(s);
284 sp = (uintptr*)(s->start<<PageShift);
286 // Coalesce with earlier, later spans.
288 if(sizeof(void*) == 8)
289 p -= (uintptr)h->arena_start >> PageShift;
290 if(p > 0 && (t = h->map[p-1]) != nil && t->state != MSpanInUse) {
291 tp = (uintptr*)(t->start<<PageShift);
292 *tp |= *sp; // propagate "needs zeroing" mark
294 s->npages += t->npages;
297 runtime_MSpanList_Remove(t);
298 t->state = MSpanDead;
299 runtime_FixAlloc_Free(&h->spanalloc, t);
300 mstats.mspan_inuse = h->spanalloc.inuse;
301 mstats.mspan_sys = h->spanalloc.sys;
303 if(p+s->npages < nelem(h->map) && (t = h->map[p+s->npages]) != nil && t->state != MSpanInUse) {
304 tp = (uintptr*)(t->start<<PageShift);
305 *sp |= *tp; // propagate "needs zeroing" mark
306 s->npages += t->npages;
307 h->map[p + s->npages - 1] = s;
308 runtime_MSpanList_Remove(t);
309 t->state = MSpanDead;
310 runtime_FixAlloc_Free(&h->spanalloc, t);
311 mstats.mspan_inuse = h->spanalloc.inuse;
312 mstats.mspan_sys = h->spanalloc.sys;
315 // Insert s into appropriate list.
316 if(s->npages < nelem(h->free))
317 runtime_MSpanList_Insert(&h->free[s->npages], s);
319 runtime_MSpanList_Insert(&h->large, s);
321 // TODO(rsc): IncrementalScavenge() to return memory to OS.
324 // Initialize a new span with the given start and npages.
326 runtime_MSpan_Init(MSpan *span, PageID start, uintptr npages)
331 span->npages = npages;
332 span->freelist = nil;
338 // Initialize an empty doubly-linked list.
340 runtime_MSpanList_Init(MSpan *list)
342 list->state = MSpanListHead;
348 runtime_MSpanList_Remove(MSpan *span)
350 if(span->prev == nil && span->next == nil)
352 span->prev->next = span->next;
353 span->next->prev = span->prev;
359 runtime_MSpanList_IsEmpty(MSpan *list)
361 return list->next == list;
365 runtime_MSpanList_Insert(MSpan *list, MSpan *span)
367 if(span->next != nil || span->prev != nil) {
368 // runtime_printf("failed MSpanList_Insert %p %p %p\n", span, span->next, span->prev);
369 runtime_throw("MSpanList_Insert");
371 span->next = list->next;
373 span->next->prev = span;
374 span->prev->next = span;