1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
|
// 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.
// See malloc.h for overview.
//
// TODO(rsc): double-check stats.
package runtime
#include <stddef.h>
#include <errno.h>
#include <stdlib.h>
#include "go-alloc.h"
#include "runtime.h"
#include "malloc.h"
#include "go-string.h"
#include "interface.h"
#include "go-type.h"
typedef struct __go_empty_interface Eface;
typedef struct __go_type_descriptor Type;
typedef struct __go_func_type FuncType;
MHeap runtime_mheap;
extern MStats mstats; // defined in extern.go
extern volatile int32 runtime_MemProfileRate
__asm__ ("libgo_runtime.runtime.MemProfileRate");
// Allocate an object of at least size bytes.
// Small objects are allocated from the per-thread cache's free lists.
// Large objects (> 32 kB) are allocated straight from the heap.
void*
runtime_mallocgc(uintptr size, uint32 flag, int32 dogc, int32 zeroed)
{
int32 sizeclass, rate;
MCache *c;
uintptr npages;
MSpan *s;
void *v;
if(!__sync_bool_compare_and_swap(&m->mallocing, 0, 1))
runtime_throw("malloc/free - deadlock");
if(size == 0)
size = 1;
c = m->mcache;
c->local_nmalloc++;
if(size <= MaxSmallSize) {
// Allocate from mcache free lists.
sizeclass = runtime_SizeToClass(size);
size = runtime_class_to_size[sizeclass];
v = runtime_MCache_Alloc(c, sizeclass, size, zeroed);
if(v == nil)
runtime_throw("out of memory");
c->local_alloc += size;
c->local_total_alloc += size;
c->local_by_size[sizeclass].nmalloc++;
} else {
// TODO(rsc): Report tracebacks for very large allocations.
// Allocate directly from heap.
npages = size >> PageShift;
if((size & PageMask) != 0)
npages++;
s = runtime_MHeap_Alloc(&runtime_mheap, npages, 0, 1);
if(s == nil)
runtime_throw("out of memory");
size = npages<<PageShift;
c->local_alloc += size;
c->local_total_alloc += size;
v = (void*)(s->start << PageShift);
// setup for mark sweep
runtime_markspan(v, 0, 0, true);
}
if(!(flag & FlagNoGC))
runtime_markallocated(v, size, (flag&FlagNoPointers) != 0);
__sync_bool_compare_and_swap(&m->mallocing, 1, 0);
if(__sync_bool_compare_and_swap(&m->gcing, 1, 0)) {
if(!(flag & FlagNoProfiling))
__go_run_goroutine_gc(0);
else {
// We are being called from the profiler. Tell it
// to invoke the garbage collector when it is
// done. No need to use a sync function here.
m->gcing_for_prof = 1;
}
}
if(!(flag & FlagNoProfiling) && (rate = runtime_MemProfileRate) > 0) {
if(size >= (uint32) rate)
goto profile;
if((uint32) m->mcache->next_sample > size)
m->mcache->next_sample -= size;
else {
// pick next profile time
if(rate > 0x3fffffff) // make 2*rate not overflow
rate = 0x3fffffff;
m->mcache->next_sample = runtime_fastrand1() % (2*rate);
profile:
runtime_setblockspecial(v);
runtime_MProf_Malloc(v, size);
}
}
if(dogc && mstats.heap_alloc >= mstats.next_gc)
runtime_gc(0);
return v;
}
void*
__go_alloc(uintptr size)
{
return runtime_mallocgc(size, 0, 0, 1);
}
// Free the object whose base pointer is v.
void
__go_free(void *v)
{
int32 sizeclass;
MSpan *s;
MCache *c;
uint32 prof;
uintptr size;
if(v == nil)
return;
// If you change this also change mgc0.c:/^sweepspan,
// which has a copy of the guts of free.
if(!__sync_bool_compare_and_swap(&m->mallocing, 0, 1))
runtime_throw("malloc/free - deadlock");
if(!runtime_mlookup(v, nil, nil, &s)) {
// runtime_printf("free %p: not an allocated block\n", v);
runtime_throw("free runtime_mlookup");
}
prof = runtime_blockspecial(v);
// Find size class for v.
sizeclass = s->sizeclass;
c = m->mcache;
if(sizeclass == 0) {
// Large object.
size = s->npages<<PageShift;
*(uintptr*)(s->start<<PageShift) = 1; // mark as "needs to be zeroed"
// Must mark v freed before calling unmarkspan and MHeap_Free:
// they might coalesce v into other spans and change the bitmap further.
runtime_markfreed(v, size);
runtime_unmarkspan(v, 1<<PageShift);
runtime_MHeap_Free(&runtime_mheap, s, 1);
} else {
// Small object.
size = runtime_class_to_size[sizeclass];
if(size > sizeof(uintptr))
((uintptr*)v)[1] = 1; // mark as "needs to be zeroed"
// Must mark v freed before calling MCache_Free:
// it might coalesce v and other blocks into a bigger span
// and change the bitmap further.
runtime_markfreed(v, size);
c->local_by_size[sizeclass].nfree++;
runtime_MCache_Free(c, v, sizeclass, size);
}
c->local_alloc -= size;
if(prof)
runtime_MProf_Free(v, size);
__sync_bool_compare_and_swap(&m->mallocing, 1, 0);
if(__sync_bool_compare_and_swap(&m->gcing, 1, 0))
__go_run_goroutine_gc(1);
}
int32
runtime_mlookup(void *v, byte **base, uintptr *size, MSpan **sp)
{
uintptr n, i;
byte *p;
MSpan *s;
m->mcache->local_nlookup++;
s = runtime_MHeap_LookupMaybe(&runtime_mheap, v);
if(sp)
*sp = s;
if(s == nil) {
runtime_checkfreed(v, 1);
if(base)
*base = nil;
if(size)
*size = 0;
return 0;
}
p = (byte*)((uintptr)s->start<<PageShift);
if(s->sizeclass == 0) {
// Large object.
if(base)
*base = p;
if(size)
*size = s->npages<<PageShift;
return 1;
}
if((byte*)v >= (byte*)s->limit) {
// pointers past the last block do not count as pointers.
return 0;
}
n = runtime_class_to_size[s->sizeclass];
if(base) {
i = ((byte*)v - p)/n;
*base = p + i*n;
}
if(size)
*size = n;
return 1;
}
MCache*
runtime_allocmcache(void)
{
MCache *c;
if(!__sync_bool_compare_and_swap(&m->mallocing, 0, 1))
runtime_throw("allocmcache - deadlock");
runtime_lock(&runtime_mheap);
c = runtime_FixAlloc_Alloc(&runtime_mheap.cachealloc);
// Clear the free list used by FixAlloc; assume the rest is zeroed.
c->list[0].list = nil;
mstats.mcache_inuse = runtime_mheap.cachealloc.inuse;
mstats.mcache_sys = runtime_mheap.cachealloc.sys;
runtime_unlock(&runtime_mheap);
__sync_bool_compare_and_swap(&m->mallocing, 1, 0);
if(__sync_bool_compare_and_swap(&m->gcing, 1, 0))
__go_run_goroutine_gc(2);
return c;
}
void
runtime_purgecachedstats(M* m)
{
MCache *c;
// Protected by either heap or GC lock.
c = m->mcache;
mstats.heap_alloc += c->local_cachealloc;
c->local_cachealloc = 0;
mstats.heap_objects += c->local_objects;
c->local_objects = 0;
mstats.nmalloc += c->local_nmalloc;
c->local_nmalloc = 0;
mstats.nfree += c->local_nfree;
c->local_nfree = 0;
mstats.nlookup += c->local_nlookup;
c->local_nlookup = 0;
mstats.alloc += c->local_alloc;
c->local_alloc= 0;
mstats.total_alloc += c->local_total_alloc;
c->local_total_alloc= 0;
}
extern uintptr runtime_sizeof_C_MStats
__asm__ ("libgo_runtime.runtime.Sizeof_C_MStats");
#define MaxArena32 (2U<<30)
void
runtime_mallocinit(void)
{
byte *p;
uintptr arena_size, bitmap_size;
extern byte end[];
runtime_sizeof_C_MStats = sizeof(MStats);
runtime_InitSizes();
// Set up the allocation arena, a contiguous area of memory where
// allocated data will be found. The arena begins with a bitmap large
// enough to hold 4 bits per allocated word.
if(sizeof(void*) == 8) {
// On a 64-bit machine, allocate from a single contiguous reservation.
// 16 GB should be big enough for now.
//
// The code will work with the reservation at any address, but ask
// SysReserve to use 0x000000f800000000 if possible.
// Allocating a 16 GB region takes away 36 bits, and the amd64
// doesn't let us choose the top 17 bits, so that leaves the 11 bits
// in the middle of 0x00f8 for us to choose. Choosing 0x00f8 means
// that the valid memory addresses will begin 0x00f8, 0x00f9, 0x00fa, 0x00fb.
// None of the bytes f8 f9 fa fb can appear in valid UTF-8, and
// they are otherwise as far from ff (likely a common byte) as possible.
// Choosing 0x00 for the leading 6 bits was more arbitrary, but it
// is not a common ASCII code point either. Using 0x11f8 instead
// caused out of memory errors on OS X during thread allocations.
// These choices are both for debuggability and to reduce the
// odds of the conservative garbage collector not collecting memory
// because some non-pointer block of memory had a bit pattern
// that matched a memory address.
//
// Actually we reserve 17 GB (because the bitmap ends up being 1 GB)
// but it hardly matters: fc is not valid UTF-8 either, and we have to
// allocate 15 GB before we get that far.
arena_size = (uintptr)(16LL<<30);
bitmap_size = arena_size / (sizeof(void*)*8/4);
p = runtime_SysReserve((void*)(0x00f8ULL<<32), bitmap_size + arena_size);
if(p == nil)
runtime_throw("runtime: cannot reserve arena virtual address space");
} else {
// On a 32-bit machine, we can't typically get away
// with a giant virtual address space reservation.
// Instead we map the memory information bitmap
// immediately after the data segment, large enough
// to handle another 2GB of mappings (256 MB),
// along with a reservation for another 512 MB of memory.
// When that gets used up, we'll start asking the kernel
// for any memory anywhere and hope it's in the 2GB
// following the bitmap (presumably the executable begins
// near the bottom of memory, so we'll have to use up
// most of memory before the kernel resorts to giving out
// memory before the beginning of the text segment).
//
// Alternatively we could reserve 512 MB bitmap, enough
// for 4GB of mappings, and then accept any memory the
// kernel threw at us, but normally that's a waste of 512 MB
// of address space, which is probably too much in a 32-bit world.
bitmap_size = MaxArena32 / (sizeof(void*)*8/4);
arena_size = 512<<20;
// SysReserve treats the address we ask for, end, as a hint,
// not as an absolute requirement. If we ask for the end
// of the data segment but the operating system requires
// a little more space before we can start allocating, it will
// give out a slightly higher pointer. That's fine.
// Run with what we get back.
p = runtime_SysReserve(end, bitmap_size + arena_size);
if(p == nil)
runtime_throw("runtime: cannot reserve arena virtual address space");
}
if((uintptr)p & (((uintptr)1<<PageShift)-1))
runtime_throw("runtime: SysReserve returned unaligned address");
runtime_mheap.bitmap = p;
runtime_mheap.arena_start = p + bitmap_size;
runtime_mheap.arena_used = runtime_mheap.arena_start;
runtime_mheap.arena_end = runtime_mheap.arena_start + arena_size;
// Initialize the rest of the allocator.
runtime_MHeap_Init(&runtime_mheap, runtime_SysAlloc);
m->mcache = runtime_allocmcache();
// Initialize malloc profiling.
runtime_Mprof_Init();
// Initialize finalizer.
runtime_initfintab();
// See if it works.
runtime_free(runtime_malloc(1));
}
void*
runtime_MHeap_SysAlloc(MHeap *h, uintptr n)
{
byte *p;
if(n <= (uintptr)(h->arena_end - h->arena_used)) {
// Keep taking from our reservation.
p = h->arena_used;
runtime_SysMap(p, n);
h->arena_used += n;
runtime_MHeap_MapBits(h);
return p;
}
// On 64-bit, our reservation is all we have.
if(sizeof(void*) == 8)
return nil;
// On 32-bit, once the reservation is gone we can
// try to get memory at a location chosen by the OS
// and hope that it is in the range we allocated bitmap for.
p = runtime_SysAlloc(n);
if(p == nil)
return nil;
if(p < h->arena_start || (uintptr)(p+n - h->arena_start) >= MaxArena32) {
runtime_printf("runtime: memory allocated by OS not in usable range\n");
runtime_SysFree(p, n);
return nil;
}
if(p+n > h->arena_used) {
h->arena_used = p+n;
if(h->arena_used > h->arena_end)
h->arena_end = h->arena_used;
runtime_MHeap_MapBits(h);
}
return p;
}
// Runtime stubs.
void*
runtime_mal(uintptr n)
{
return runtime_mallocgc(n, 0, 1, 1);
}
func new(n uint32) (ret *uint8) {
ret = runtime_mal(n);
}
func Alloc(n uintptr) (p *byte) {
p = runtime_malloc(n);
}
func Free(p *byte) {
runtime_free(p);
}
func Lookup(p *byte) (base *byte, size uintptr) {
runtime_mlookup(p, &base, &size, nil);
}
func GC() {
runtime_gc(1);
}
func SetFinalizer(obj Eface, finalizer Eface) {
byte *base;
uintptr size;
const FuncType *ft;
if(obj.__type_descriptor == nil) {
// runtime_printf("runtime.SetFinalizer: first argument is nil interface\n");
throw:
runtime_throw("runtime.SetFinalizer");
}
if(obj.__type_descriptor->__code != GO_PTR) {
// runtime_printf("runtime.SetFinalizer: first argument is %S, not pointer\n", *obj.type->string);
goto throw;
}
if(!runtime_mlookup(obj.__object, &base, &size, nil) || obj.__object != base) {
// runtime_printf("runtime.SetFinalizer: pointer not at beginning of allocated block\n");
goto throw;
}
ft = nil;
if(finalizer.__type_descriptor != nil) {
if(finalizer.__type_descriptor->__code != GO_FUNC) {
badfunc:
// runtime_printf("runtime.SetFinalizer: second argument is %S, not func(%S)\n", *finalizer.type->string, *obj.type->string);
goto throw;
}
ft = (const FuncType*)finalizer.__type_descriptor;
if(ft->__dotdotdot || ft->__in.__count != 1 || !__go_type_descriptors_equal(*(Type**)ft->__in.__values, obj.__type_descriptor))
goto badfunc;
if(runtime_getfinalizer(obj.__object, 0)) {
// runtime_printf("runtime.SetFinalizer: finalizer already set");
goto throw;
}
}
runtime_addfinalizer(obj.__object, finalizer.__type_descriptor != nil ? *(void**)finalizer.__object : nil, ft);
}
|