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Side by Side Diff: third_party/sqlite/src/mem5.c

Issue 3108030: Move bundled copy of sqlite one level deeper to better separate it... (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/src/
Patch Set: Created 10 years, 4 months ago
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1 /*
2 ** 2007 October 14
3 **
4 ** The author disclaims copyright to this source code. In place of
5 ** a legal notice, here is a blessing:
6 **
7 ** May you do good and not evil.
8 ** May you find forgiveness for yourself and forgive others.
9 ** May you share freely, never taking more than you give.
10 **
11 *************************************************************************
12 ** This file contains the C functions that implement a memory
13 ** allocation subsystem for use by SQLite.
14 **
15 ** This version of the memory allocation subsystem omits all
16 ** use of malloc(). The application gives SQLite a block of memory
17 ** before calling sqlite3_initialize() from which allocations
18 ** are made and returned by the xMalloc() and xRealloc()
19 ** implementations. Once sqlite3_initialize() has been called,
20 ** the amount of memory available to SQLite is fixed and cannot
21 ** be changed.
22 **
23 ** This version of the memory allocation subsystem is included
24 ** in the build only if SQLITE_ENABLE_MEMSYS5 is defined.
25 **
26 ** This memory allocator uses the following algorithm:
27 **
28 ** 1. All memory allocations sizes are rounded up to a power of 2.
29 **
30 ** 2. If two adjacent free blocks are the halves of a larger block,
31 ** then the two blocks are coalesed into the single larger block.
32 **
33 ** 3. New memory is allocated from the first available free block.
34 **
35 ** This algorithm is described in: J. M. Robson. "Bounds for Some Functions
36 ** Concerning Dynamic Storage Allocation". Journal of the Association for
37 ** Computing Machinery, Volume 21, Number 8, July 1974, pages 491-499.
38 **
39 ** Let n be the size of the largest allocation divided by the minimum
40 ** allocation size (after rounding all sizes up to a power of 2.) Let M
41 ** be the maximum amount of memory ever outstanding at one time. Let
42 ** N be the total amount of memory available for allocation. Robson
43 ** proved that this memory allocator will never breakdown due to
44 ** fragmentation as long as the following constraint holds:
45 **
46 ** N >= M*(1 + log2(n)/2) - n + 1
47 **
48 ** The sqlite3_status() logic tracks the maximum values of n and M so
49 ** that an application can, at any time, verify this constraint.
50 */
51 #include "sqliteInt.h"
52
53 /*
54 ** This version of the memory allocator is used only when
55 ** SQLITE_ENABLE_MEMSYS5 is defined.
56 */
57 #ifdef SQLITE_ENABLE_MEMSYS5
58
59 /*
60 ** A minimum allocation is an instance of the following structure.
61 ** Larger allocations are an array of these structures where the
62 ** size of the array is a power of 2.
63 **
64 ** The size of this object must be a power of two. That fact is
65 ** verified in memsys5Init().
66 */
67 typedef struct Mem5Link Mem5Link;
68 struct Mem5Link {
69 int next; /* Index of next free chunk */
70 int prev; /* Index of previous free chunk */
71 };
72
73 /*
74 ** Maximum size of any allocation is ((1<<LOGMAX)*mem5.szAtom). Since
75 ** mem5.szAtom is always at least 8 and 32-bit integers are used,
76 ** it is not actually possible to reach this limit.
77 */
78 #define LOGMAX 30
79
80 /*
81 ** Masks used for mem5.aCtrl[] elements.
82 */
83 #define CTRL_LOGSIZE 0x1f /* Log2 Size of this block */
84 #define CTRL_FREE 0x20 /* True if not checked out */
85
86 /*
87 ** All of the static variables used by this module are collected
88 ** into a single structure named "mem5". This is to keep the
89 ** static variables organized and to reduce namespace pollution
90 ** when this module is combined with other in the amalgamation.
91 */
92 static SQLITE_WSD struct Mem5Global {
93 /*
94 ** Memory available for allocation
95 */
96 int szAtom; /* Smallest possible allocation in bytes */
97 int nBlock; /* Number of szAtom sized blocks in zPool */
98 u8 *zPool; /* Memory available to be allocated */
99
100 /*
101 ** Mutex to control access to the memory allocation subsystem.
102 */
103 sqlite3_mutex *mutex;
104
105 /*
106 ** Performance statistics
107 */
108 u64 nAlloc; /* Total number of calls to malloc */
109 u64 totalAlloc; /* Total of all malloc calls - includes internal frag */
110 u64 totalExcess; /* Total internal fragmentation */
111 u32 currentOut; /* Current checkout, including internal fragmentation */
112 u32 currentCount; /* Current number of distinct checkouts */
113 u32 maxOut; /* Maximum instantaneous currentOut */
114 u32 maxCount; /* Maximum instantaneous currentCount */
115 u32 maxRequest; /* Largest allocation (exclusive of internal frag) */
116
117 /*
118 ** Lists of free blocks. aiFreelist[0] is a list of free blocks of
119 ** size mem5.szAtom. aiFreelist[1] holds blocks of size szAtom*2.
120 ** and so forth.
121 */
122 int aiFreelist[LOGMAX+1];
123
124 /*
125 ** Space for tracking which blocks are checked out and the size
126 ** of each block. One byte per block.
127 */
128 u8 *aCtrl;
129
130 } mem5 = { 0 };
131
132 /*
133 ** Access the static variable through a macro for SQLITE_OMIT_WSD
134 */
135 #define mem5 GLOBAL(struct Mem5Global, mem5)
136
137 /*
138 ** Assuming mem5.zPool is divided up into an array of Mem5Link
139 ** structures, return a pointer to the idx-th such lik.
140 */
141 #define MEM5LINK(idx) ((Mem5Link *)(&mem5.zPool[(idx)*mem5.szAtom]))
142
143 /*
144 ** Unlink the chunk at mem5.aPool[i] from list it is currently
145 ** on. It should be found on mem5.aiFreelist[iLogsize].
146 */
147 static void memsys5Unlink(int i, int iLogsize){
148 int next, prev;
149 assert( i>=0 && i<mem5.nBlock );
150 assert( iLogsize>=0 && iLogsize<=LOGMAX );
151 assert( (mem5.aCtrl[i] & CTRL_LOGSIZE)==iLogsize );
152
153 next = MEM5LINK(i)->next;
154 prev = MEM5LINK(i)->prev;
155 if( prev<0 ){
156 mem5.aiFreelist[iLogsize] = next;
157 }else{
158 MEM5LINK(prev)->next = next;
159 }
160 if( next>=0 ){
161 MEM5LINK(next)->prev = prev;
162 }
163 }
164
165 /*
166 ** Link the chunk at mem5.aPool[i] so that is on the iLogsize
167 ** free list.
168 */
169 static void memsys5Link(int i, int iLogsize){
170 int x;
171 assert( sqlite3_mutex_held(mem5.mutex) );
172 assert( i>=0 && i<mem5.nBlock );
173 assert( iLogsize>=0 && iLogsize<=LOGMAX );
174 assert( (mem5.aCtrl[i] & CTRL_LOGSIZE)==iLogsize );
175
176 x = MEM5LINK(i)->next = mem5.aiFreelist[iLogsize];
177 MEM5LINK(i)->prev = -1;
178 if( x>=0 ){
179 assert( x<mem5.nBlock );
180 MEM5LINK(x)->prev = i;
181 }
182 mem5.aiFreelist[iLogsize] = i;
183 }
184
185 /*
186 ** If the STATIC_MEM mutex is not already held, obtain it now. The mutex
187 ** will already be held (obtained by code in malloc.c) if
188 ** sqlite3GlobalConfig.bMemStat is true.
189 */
190 static void memsys5Enter(void){
191 sqlite3_mutex_enter(mem5.mutex);
192 }
193 static void memsys5Leave(void){
194 sqlite3_mutex_leave(mem5.mutex);
195 }
196
197 /*
198 ** Return the size of an outstanding allocation, in bytes. The
199 ** size returned omits the 8-byte header overhead. This only
200 ** works for chunks that are currently checked out.
201 */
202 static int memsys5Size(void *p){
203 int iSize = 0;
204 if( p ){
205 int i = ((u8 *)p-mem5.zPool)/mem5.szAtom;
206 assert( i>=0 && i<mem5.nBlock );
207 iSize = mem5.szAtom * (1 << (mem5.aCtrl[i]&CTRL_LOGSIZE));
208 }
209 return iSize;
210 }
211
212 /*
213 ** Find the first entry on the freelist iLogsize. Unlink that
214 ** entry and return its index.
215 */
216 static int memsys5UnlinkFirst(int iLogsize){
217 int i;
218 int iFirst;
219
220 assert( iLogsize>=0 && iLogsize<=LOGMAX );
221 i = iFirst = mem5.aiFreelist[iLogsize];
222 assert( iFirst>=0 );
223 while( i>0 ){
224 if( i<iFirst ) iFirst = i;
225 i = MEM5LINK(i)->next;
226 }
227 memsys5Unlink(iFirst, iLogsize);
228 return iFirst;
229 }
230
231 /*
232 ** Return a block of memory of at least nBytes in size.
233 ** Return NULL if unable. Return NULL if nBytes==0.
234 **
235 ** The caller guarantees that nByte positive.
236 **
237 ** The caller has obtained a mutex prior to invoking this
238 ** routine so there is never any chance that two or more
239 ** threads can be in this routine at the same time.
240 */
241 static void *memsys5MallocUnsafe(int nByte){
242 int i; /* Index of a mem5.aPool[] slot */
243 int iBin; /* Index into mem5.aiFreelist[] */
244 int iFullSz; /* Size of allocation rounded up to power of 2 */
245 int iLogsize; /* Log2 of iFullSz/POW2_MIN */
246
247 /* nByte must be a positive */
248 assert( nByte>0 );
249
250 /* Keep track of the maximum allocation request. Even unfulfilled
251 ** requests are counted */
252 if( (u32)nByte>mem5.maxRequest ){
253 mem5.maxRequest = nByte;
254 }
255
256 /* Abort if the requested allocation size is larger than the largest
257 ** power of two that we can represent using 32-bit signed integers.
258 */
259 if( nByte > 0x40000000 ){
260 return 0;
261 }
262
263 /* Round nByte up to the next valid power of two */
264 for(iFullSz=mem5.szAtom, iLogsize=0; iFullSz<nByte; iFullSz *= 2, iLogsize++){ }
265
266 /* Make sure mem5.aiFreelist[iLogsize] contains at least one free
267 ** block. If not, then split a block of the next larger power of
268 ** two in order to create a new free block of size iLogsize.
269 */
270 for(iBin=iLogsize; mem5.aiFreelist[iBin]<0 && iBin<=LOGMAX; iBin++){}
271 if( iBin>LOGMAX ) return 0;
272 i = memsys5UnlinkFirst(iBin);
273 while( iBin>iLogsize ){
274 int newSize;
275
276 iBin--;
277 newSize = 1 << iBin;
278 mem5.aCtrl[i+newSize] = CTRL_FREE | iBin;
279 memsys5Link(i+newSize, iBin);
280 }
281 mem5.aCtrl[i] = iLogsize;
282
283 /* Update allocator performance statistics. */
284 mem5.nAlloc++;
285 mem5.totalAlloc += iFullSz;
286 mem5.totalExcess += iFullSz - nByte;
287 mem5.currentCount++;
288 mem5.currentOut += iFullSz;
289 if( mem5.maxCount<mem5.currentCount ) mem5.maxCount = mem5.currentCount;
290 if( mem5.maxOut<mem5.currentOut ) mem5.maxOut = mem5.currentOut;
291
292 /* Return a pointer to the allocated memory. */
293 return (void*)&mem5.zPool[i*mem5.szAtom];
294 }
295
296 /*
297 ** Free an outstanding memory allocation.
298 */
299 static void memsys5FreeUnsafe(void *pOld){
300 u32 size, iLogsize;
301 int iBlock;
302
303 /* Set iBlock to the index of the block pointed to by pOld in
304 ** the array of mem5.szAtom byte blocks pointed to by mem5.zPool.
305 */
306 iBlock = ((u8 *)pOld-mem5.zPool)/mem5.szAtom;
307
308 /* Check that the pointer pOld points to a valid, non-free block. */
309 assert( iBlock>=0 && iBlock<mem5.nBlock );
310 assert( ((u8 *)pOld-mem5.zPool)%mem5.szAtom==0 );
311 assert( (mem5.aCtrl[iBlock] & CTRL_FREE)==0 );
312
313 iLogsize = mem5.aCtrl[iBlock] & CTRL_LOGSIZE;
314 size = 1<<iLogsize;
315 assert( iBlock+size-1<(u32)mem5.nBlock );
316
317 mem5.aCtrl[iBlock] |= CTRL_FREE;
318 mem5.aCtrl[iBlock+size-1] |= CTRL_FREE;
319 assert( mem5.currentCount>0 );
320 assert( mem5.currentOut>=(size*mem5.szAtom) );
321 mem5.currentCount--;
322 mem5.currentOut -= size*mem5.szAtom;
323 assert( mem5.currentOut>0 || mem5.currentCount==0 );
324 assert( mem5.currentCount>0 || mem5.currentOut==0 );
325
326 mem5.aCtrl[iBlock] = CTRL_FREE | iLogsize;
327 while( ALWAYS(iLogsize<LOGMAX) ){
328 int iBuddy;
329 if( (iBlock>>iLogsize) & 1 ){
330 iBuddy = iBlock - size;
331 }else{
332 iBuddy = iBlock + size;
333 }
334 assert( iBuddy>=0 );
335 if( (iBuddy+(1<<iLogsize))>mem5.nBlock ) break;
336 if( mem5.aCtrl[iBuddy]!=(CTRL_FREE | iLogsize) ) break;
337 memsys5Unlink(iBuddy, iLogsize);
338 iLogsize++;
339 if( iBuddy<iBlock ){
340 mem5.aCtrl[iBuddy] = CTRL_FREE | iLogsize;
341 mem5.aCtrl[iBlock] = 0;
342 iBlock = iBuddy;
343 }else{
344 mem5.aCtrl[iBlock] = CTRL_FREE | iLogsize;
345 mem5.aCtrl[iBuddy] = 0;
346 }
347 size *= 2;
348 }
349 memsys5Link(iBlock, iLogsize);
350 }
351
352 /*
353 ** Allocate nBytes of memory
354 */
355 static void *memsys5Malloc(int nBytes){
356 sqlite3_int64 *p = 0;
357 if( nBytes>0 ){
358 memsys5Enter();
359 p = memsys5MallocUnsafe(nBytes);
360 memsys5Leave();
361 }
362 return (void*)p;
363 }
364
365 /*
366 ** Free memory.
367 **
368 ** The outer layer memory allocator prevents this routine from
369 ** being called with pPrior==0.
370 */
371 static void memsys5Free(void *pPrior){
372 assert( pPrior!=0 );
373 memsys5Enter();
374 memsys5FreeUnsafe(pPrior);
375 memsys5Leave();
376 }
377
378 /*
379 ** Change the size of an existing memory allocation.
380 **
381 ** The outer layer memory allocator prevents this routine from
382 ** being called with pPrior==0.
383 **
384 ** nBytes is always a value obtained from a prior call to
385 ** memsys5Round(). Hence nBytes is always a non-negative power
386 ** of two. If nBytes==0 that means that an oversize allocation
387 ** (an allocation larger than 0x40000000) was requested and this
388 ** routine should return 0 without freeing pPrior.
389 */
390 static void *memsys5Realloc(void *pPrior, int nBytes){
391 int nOld;
392 void *p;
393 assert( pPrior!=0 );
394 assert( (nBytes&(nBytes-1))==0 );
395 assert( nBytes>=0 );
396 if( nBytes==0 ){
397 return 0;
398 }
399 nOld = memsys5Size(pPrior);
400 if( nBytes<=nOld ){
401 return pPrior;
402 }
403 memsys5Enter();
404 p = memsys5MallocUnsafe(nBytes);
405 if( p ){
406 memcpy(p, pPrior, nOld);
407 memsys5FreeUnsafe(pPrior);
408 }
409 memsys5Leave();
410 return p;
411 }
412
413 /*
414 ** Round up a request size to the next valid allocation size. If
415 ** the allocation is too large to be handled by this allocation system,
416 ** return 0.
417 **
418 ** All allocations must be a power of two and must be expressed by a
419 ** 32-bit signed integer. Hence the largest allocation is 0x40000000
420 ** or 1073741824 bytes.
421 */
422 static int memsys5Roundup(int n){
423 int iFullSz;
424 if( n > 0x40000000 ) return 0;
425 for(iFullSz=mem5.szAtom; iFullSz<n; iFullSz *= 2);
426 return iFullSz;
427 }
428
429 /*
430 ** Return the ceiling of the logarithm base 2 of iValue.
431 **
432 ** Examples: memsys5Log(1) -> 0
433 ** memsys5Log(2) -> 1
434 ** memsys5Log(4) -> 2
435 ** memsys5Log(5) -> 3
436 ** memsys5Log(8) -> 3
437 ** memsys5Log(9) -> 4
438 */
439 static int memsys5Log(int iValue){
440 int iLog;
441 for(iLog=0; (1<<iLog)<iValue; iLog++);
442 return iLog;
443 }
444
445 /*
446 ** Initialize the memory allocator.
447 **
448 ** This routine is not threadsafe. The caller must be holding a mutex
449 ** to prevent multiple threads from entering at the same time.
450 */
451 static int memsys5Init(void *NotUsed){
452 int ii; /* Loop counter */
453 int nByte; /* Number of bytes of memory available to this allocator */
454 u8 *zByte; /* Memory usable by this allocator */
455 int nMinLog; /* Log base 2 of minimum allocation size in bytes */
456 int iOffset; /* An offset into mem5.aCtrl[] */
457
458 UNUSED_PARAMETER(NotUsed);
459
460 /* For the purposes of this routine, disable the mutex */
461 mem5.mutex = 0;
462
463 /* The size of a Mem5Link object must be a power of two. Verify that
464 ** this is case.
465 */
466 assert( (sizeof(Mem5Link)&(sizeof(Mem5Link)-1))==0 );
467
468 nByte = sqlite3GlobalConfig.nHeap;
469 zByte = (u8*)sqlite3GlobalConfig.pHeap;
470 assert( zByte!=0 ); /* sqlite3_config() does not allow otherwise */
471
472 nMinLog = memsys5Log(sqlite3GlobalConfig.mnReq);
473 mem5.szAtom = (1<<nMinLog);
474 while( (int)sizeof(Mem5Link)>mem5.szAtom ){
475 mem5.szAtom = mem5.szAtom << 1;
476 }
477
478 mem5.nBlock = (nByte / (mem5.szAtom+sizeof(u8)));
479 mem5.zPool = zByte;
480 mem5.aCtrl = (u8 *)&mem5.zPool[mem5.nBlock*mem5.szAtom];
481
482 for(ii=0; ii<=LOGMAX; ii++){
483 mem5.aiFreelist[ii] = -1;
484 }
485
486 iOffset = 0;
487 for(ii=LOGMAX; ii>=0; ii--){
488 int nAlloc = (1<<ii);
489 if( (iOffset+nAlloc)<=mem5.nBlock ){
490 mem5.aCtrl[iOffset] = ii | CTRL_FREE;
491 memsys5Link(iOffset, ii);
492 iOffset += nAlloc;
493 }
494 assert((iOffset+nAlloc)>mem5.nBlock);
495 }
496
497 /* If a mutex is required for normal operation, allocate one */
498 if( sqlite3GlobalConfig.bMemstat==0 ){
499 mem5.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
500 }
501
502 return SQLITE_OK;
503 }
504
505 /*
506 ** Deinitialize this module.
507 */
508 static void memsys5Shutdown(void *NotUsed){
509 UNUSED_PARAMETER(NotUsed);
510 mem5.mutex = 0;
511 return;
512 }
513
514 #ifdef SQLITE_TEST
515 /*
516 ** Open the file indicated and write a log of all unfreed memory
517 ** allocations into that log.
518 */
519 void sqlite3Memsys5Dump(const char *zFilename){
520 FILE *out;
521 int i, j, n;
522 int nMinLog;
523
524 if( zFilename==0 || zFilename[0]==0 ){
525 out = stdout;
526 }else{
527 out = fopen(zFilename, "w");
528 if( out==0 ){
529 fprintf(stderr, "** Unable to output memory debug output log: %s **\n",
530 zFilename);
531 return;
532 }
533 }
534 memsys5Enter();
535 nMinLog = memsys5Log(mem5.szAtom);
536 for(i=0; i<=LOGMAX && i+nMinLog<32; i++){
537 for(n=0, j=mem5.aiFreelist[i]; j>=0; j = MEM5LINK(j)->next, n++){}
538 fprintf(out, "freelist items of size %d: %d\n", mem5.szAtom << i, n);
539 }
540 fprintf(out, "mem5.nAlloc = %llu\n", mem5.nAlloc);
541 fprintf(out, "mem5.totalAlloc = %llu\n", mem5.totalAlloc);
542 fprintf(out, "mem5.totalExcess = %llu\n", mem5.totalExcess);
543 fprintf(out, "mem5.currentOut = %u\n", mem5.currentOut);
544 fprintf(out, "mem5.currentCount = %u\n", mem5.currentCount);
545 fprintf(out, "mem5.maxOut = %u\n", mem5.maxOut);
546 fprintf(out, "mem5.maxCount = %u\n", mem5.maxCount);
547 fprintf(out, "mem5.maxRequest = %u\n", mem5.maxRequest);
548 memsys5Leave();
549 if( out==stdout ){
550 fflush(stdout);
551 }else{
552 fclose(out);
553 }
554 }
555 #endif
556
557 /*
558 ** This routine is the only routine in this file with external
559 ** linkage. It returns a pointer to a static sqlite3_mem_methods
560 ** struct populated with the memsys5 methods.
561 */
562 const sqlite3_mem_methods *sqlite3MemGetMemsys5(void){
563 static const sqlite3_mem_methods memsys5Methods = {
564 memsys5Malloc,
565 memsys5Free,
566 memsys5Realloc,
567 memsys5Size,
568 memsys5Roundup,
569 memsys5Init,
570 memsys5Shutdown,
571 0
572 };
573 return &memsys5Methods;
574 }
575
576 #endif /* SQLITE_ENABLE_MEMSYS5 */
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