1 /*
2 A version of malloc/free/realloc written by Doug Lea and released to the
3 public domain. Send questions/comments/complaints/performance data
4 to dl@cs.oswego.edu
5
6 * VERSION 2.6.6 Sun Mar 5 19:10:03 2000 Doug Lea (dl at gee)
7
8 Note: There may be an updated version of this malloc obtainable at
9 ftp://g.oswego.edu/pub/misc/malloc.c
10 Check before installing!
11
12 * Why use this malloc?
13
14 This is not the fastest, most space-conserving, most portable, or
15 most tunable malloc ever written. However it is among the fastest
16 while also being among the most space-conserving, portable and tunable.
17 Consistent balance across these factors results in a good general-purpose
18 allocator. For a high-level description, see
19 http://g.oswego.edu/dl/html/malloc.html
20
21 * Synopsis of public routines
22
23 (Much fuller descriptions are contained in the program documentation below.)
24
25 malloc(size_t n);
26 Return a pointer to a newly allocated chunk of at least n bytes, or null
27 if no space is available.
28 free(Void_t* p);
29 Release the chunk of memory pointed to by p, or no effect if p is null.
30 realloc(Void_t* p, size_t n);
31 Return a pointer to a chunk of size n that contains the same data
32 as does chunk p up to the minimum of (n, p's size) bytes, or null
33 if no space is available. The returned pointer may or may not be
34 the same as p. If p is null, equivalent to malloc. Unless the
35 #define REALLOC_ZERO_BYTES_FREES below is set, realloc with a
36 size argument of zero (re)allocates a minimum-sized chunk.
37 memalign(size_t alignment, size_t n);
38 Return a pointer to a newly allocated chunk of n bytes, aligned
39 in accord with the alignment argument, which must be a power of
40 two.
41 valloc(size_t n);
42 Equivalent to memalign(pagesize, n), where pagesize is the page
43 size of the system (or as near to this as can be figured out from
44 all the includes/defines below.)
45 pvalloc(size_t n);
46 Equivalent to valloc(minimum-page-that-holds(n)), that is,
47 round up n to nearest pagesize.
48 calloc(size_t unit, size_t quantity);
49 Returns a pointer to quantity * unit bytes, with all locations
50 set to zero.
51 cfree(Void_t* p);
52 Equivalent to free(p).
53 malloc_trim(size_t pad);
54 Release all but pad bytes of freed top-most memory back
55 to the system. Return 1 if successful, else 0.
56 malloc_usable_size(Void_t* p);
57 Report the number usable allocated bytes associated with allocated
58 chunk p. This may or may not report more bytes than were requested,
59 due to alignment and minimum size constraints.
60 malloc_stats();
61 Prints brief summary statistics on stderr.
62 mallinfo()
63 Returns (by copy) a struct containing various summary statistics.
64 mallopt(int parameter_number, int parameter_value)
65 Changes one of the tunable parameters described below. Returns
66 1 if successful in changing the parameter, else 0.
67
68 * Vital statistics:
69
70 Alignment: 8-byte
71 8 byte alignment is currently hardwired into the design. This
72 seems to suffice for all current machines and C compilers.
73
74 Assumed pointer representation: 4 or 8 bytes
75 Code for 8-byte pointers is untested by me but has worked
76 reliably by Wolfram Gloger, who contributed most of the
77 changes supporting this.
78
79 Assumed size_t representation: 4 or 8 bytes
80 Note that size_t is allowed to be 4 bytes even if pointers are 8.
81
82 Minimum overhead per allocated chunk: 4 or 8 bytes
83 Each malloced chunk has a hidden overhead of 4 bytes holding size
84 and status information.
85
86 Minimum allocated size: 4-byte ptrs: 16 bytes (including 4 overhead)
87 8-byte ptrs: 24/32 bytes (including, 4/8 overhead)
88
89 When a chunk is freed, 12 (for 4byte ptrs) or 20 (for 8 byte
90 ptrs but 4 byte size) or 24 (for 8/8) additional bytes are
91 needed; 4 (8) for a trailing size field
92 and 8 (16) bytes for free list pointers. Thus, the minimum
93 allocatable size is 16/24/32 bytes.
94
95 Even a request for zero bytes (i.e., malloc(0)) returns a
96 pointer to something of the minimum allocatable size.
97
98 Maximum allocated size: 4-byte size_t: 2^31 - 8 bytes
99 8-byte size_t: 2^63 - 16 bytes
100
101 It is assumed that (possibly signed) size_t bit values suffice to
102 represent chunk sizes. `Possibly signed' is due to the fact
103 that `size_t' may be defined on a system as either a signed or
104 an unsigned type. To be conservative, values that would appear
105 as negative numbers are avoided.
106 Requests for sizes with a negative sign bit when the request
107 size is treaded as a long will return null.
108
109 Maximum overhead wastage per allocated chunk: normally 15 bytes
110
111 Alignnment demands, plus the minimum allocatable size restriction
112 make the normal worst-case wastage 15 bytes (i.e., up to 15
113 more bytes will be allocated than were requested in malloc), with
114 two exceptions:
115 1. Because requests for zero bytes allocate non-zero space,
116 the worst case wastage for a request of zero bytes is 24 bytes.
117 2. For requests >= mmap_threshold that are serviced via
118 mmap(), the worst case wastage is 8 bytes plus the remainder
119 from a system page (the minimal mmap unit); typically 4096 bytes.
120
121 * Limitations
122
123 Here are some features that are NOT currently supported
124
125 * No user-definable hooks for callbacks and the like.
126 * No automated mechanism for fully checking that all accesses
127 to malloced memory stay within their bounds.
128 * No support for compaction.
129
130 * Synopsis of compile-time options:
131
132 People have reported using previous versions of this malloc on all
133 versions of Unix, sometimes by tweaking some of the defines
134 below. It has been tested most extensively on Solaris and
135 Linux. It is also reported to work on WIN32 platforms.
136 People have also reported adapting this malloc for use in
137 stand-alone embedded systems.
138
139 The implementation is in straight, hand-tuned ANSI C. Among other
140 consequences, it uses a lot of macros. Because of this, to be at
141 all usable, this code should be compiled using an optimizing compiler
142 (for example gcc -O2) that can simplify expressions and control
143 paths.
144
145 __STD_C (default: derived from C compiler defines)
146 Nonzero if using ANSI-standard C compiler, a C++ compiler, or
147 a C compiler sufficiently close to ANSI to get away with it.
148 DEBUG (default: NOT defined)
149 Define to enable debugging. Adds fairly extensive assertion-based
150 checking to help track down memory errors, but noticeably slows down
151 execution.
152 REALLOC_ZERO_BYTES_FREES (default: NOT defined)
153 Define this if you think that realloc(p, 0) should be equivalent
154 to free(p). Otherwise, since malloc returns a unique pointer for
155 malloc(0), so does realloc(p, 0).
156 HAVE_MEMCPY (default: defined)
157 Define if you are not otherwise using ANSI STD C, but still
158 have memcpy and memset in your C library and want to use them.
159 Otherwise, simple internal versions are supplied.
160 USE_MEMCPY (default: 1 if HAVE_MEMCPY is defined, 0 otherwise)
161 Define as 1 if you want the C library versions of memset and
162 memcpy called in realloc and calloc (otherwise macro versions are used).
163 At least on some platforms, the simple macro versions usually
164 outperform libc versions.
165 HAVE_MMAP (default: defined as 1)
166 Define to non-zero to optionally make malloc() use mmap() to
167 allocate very large blocks.
168 HAVE_MREMAP (default: defined as 0 unless Linux libc set)
169 Define to non-zero to optionally make realloc() use mremap() to
170 reallocate very large blocks.
171 malloc_getpagesize (default: derived from system #includes)
172 Either a constant or routine call returning the system page size.
173 HAVE_USR_INCLUDE_MALLOC_H (default: NOT defined)
174 Optionally define if you are on a system with a /usr/include/malloc.h
175 that declares struct mallinfo. It is not at all necessary to
176 define this even if you do, but will ensure consistency.
177 INTERNAL_SIZE_T (default: size_t)
178 Define to a 32-bit type (probably `unsigned int') if you are on a
179 64-bit machine, yet do not want or need to allow malloc requests of
180 greater than 2^31 to be handled. This saves space, especially for
181 very small chunks.
182 INTERNAL_LINUX_C_LIB (default: NOT defined)
183 Defined only when compiled as part of Linux libc.
184 Also note that there is some odd internal name-mangling via defines
185 (for example, internally, `malloc' is named `mALLOc') needed
186 when compiling in this case. These look funny but don't otherwise
187 affect anything.
188 WIN32 (default: undefined)
189 Define this on MS win (95, nt) platforms to compile in sbrk emulation.
190 LACKS_UNISTD_H (default: undefined if not WIN32)
191 Define this if your system does not have a <unistd.h>.
192 LACKS_SYS_PARAM_H (default: undefined if not WIN32)
193 Define this if your system does not have a <sys/param.h>.
194 MORECORE (default: sbrk)
195 The name of the routine to call to obtain more memory from the system.
196 MORECORE_FAILURE (default: -1)
197 The value returned upon failure of MORECORE.
198 MORECORE_CLEARS (default 1)
199 true (1) if the routine mapped to MORECORE zeroes out memory (which
200 holds for sbrk).
201 DEFAULT_TRIM_THRESHOLD
202 DEFAULT_TOP_PAD
203 DEFAULT_MMAP_THRESHOLD
204 DEFAULT_MMAP_MAX
205 Default values of tunable parameters (described in detail below)
206 controlling interaction with host system routines (sbrk, mmap, etc).
207 These values may also be changed dynamically via mallopt(). The
208 preset defaults are those that give best performance for typical
209 programs/systems.
210 USE_DL_PREFIX (default: undefined)
211 Prefix all public routines with the string 'dl'. Useful to
212 quickly avoid procedure declaration conflicts and linker symbol
213 conflicts with existing memory allocation routines.
214
215
216 */
217
218
219 #ifndef __MALLOC_H__
220 #define __MALLOC_H__
221
222 /* Preliminaries */
223
224 #ifndef __STD_C
225 #ifdef __STDC__
226 #define __STD_C 1
227 #else
228 #if __cplusplus
229 #define __STD_C 1
230 #else
231 #define __STD_C 0
232 #endif /*__cplusplus*/
233 #endif /*__STDC__*/
234 #endif /*__STD_C*/
235
236 #ifndef Void_t
237 #if (__STD_C || defined(WIN32))
238 #define Void_t void
239 #else
240 #define Void_t char
241 #endif
242 #endif /*Void_t*/
243
244 #if __STD_C
245 #include <linux/stddef.h> /* for size_t */
246 #else
247 #include <sys/types.h>
248 #endif /* __STD_C */
249
250 #ifdef __cplusplus
251 extern "C" {
252 #endif
253
254 #if 0 /* not for U-Boot */
255 #include <stdio.h> /* needed for malloc_stats */
256 #endif
257
258
259 /*
260 Compile-time options
261 */
262
263
264 /*
265 Debugging:
266
267 Because freed chunks may be overwritten with link fields, this
268 malloc will often die when freed memory is overwritten by user
269 programs. This can be very effective (albeit in an annoying way)
270 in helping track down dangling pointers.
271
272 If you compile with -DDEBUG, a number of assertion checks are
273 enabled that will catch more memory errors. You probably won't be
274 able to make much sense of the actual assertion errors, but they
275 should help you locate incorrectly overwritten memory. The
276 checking is fairly extensive, and will slow down execution
277 noticeably. Calling malloc_stats or mallinfo with DEBUG set will
278 attempt to check every non-mmapped allocated and free chunk in the
279 course of computing the summmaries. (By nature, mmapped regions
280 cannot be checked very much automatically.)
281
282 Setting DEBUG may also be helpful if you are trying to modify
283 this code. The assertions in the check routines spell out in more
284 detail the assumptions and invariants underlying the algorithms.
285
286 */
287
288 /*
289 INTERNAL_SIZE_T is the word-size used for internal bookkeeping
290 of chunk sizes. On a 64-bit machine, you can reduce malloc
291 overhead by defining INTERNAL_SIZE_T to be a 32 bit `unsigned int'
292 at the expense of not being able to handle requests greater than
293 2^31. This limitation is hardly ever a concern; you are encouraged
294 to set this. However, the default version is the same as size_t.
295 */
296
297 #ifndef INTERNAL_SIZE_T
298 #define INTERNAL_SIZE_T size_t
299 #endif
300
301 /*
302 REALLOC_ZERO_BYTES_FREES should be set if a call to
303 realloc with zero bytes should be the same as a call to free.
304 Some people think it should. Otherwise, since this malloc
305 returns a unique pointer for malloc(0), so does realloc(p, 0).
306 */
307
308
309 /* #define REALLOC_ZERO_BYTES_FREES */
310
311
312 /*
313 WIN32 causes an emulation of sbrk to be compiled in
314 mmap-based options are not currently supported in WIN32.
315 */
316
317 /* #define WIN32 */
318 #ifdef WIN32
319 #define MORECORE wsbrk
320 #define HAVE_MMAP 0
321
322 #define LACKS_UNISTD_H
323 #define LACKS_SYS_PARAM_H
324
325 /*
326 Include 'windows.h' to get the necessary declarations for the
327 Microsoft Visual C++ data structures and routines used in the 'sbrk'
328 emulation.
329
330 Define WIN32_LEAN_AND_MEAN so that only the essential Microsoft
331 Visual C++ header files are included.
332 */
333 #define WIN32_LEAN_AND_MEAN
334 #include <windows.h>
335 #endif
336
337
338 /*
339 HAVE_MEMCPY should be defined if you are not otherwise using
340 ANSI STD C, but still have memcpy and memset in your C library
341 and want to use them in calloc and realloc. Otherwise simple
342 macro versions are defined here.
343
344 USE_MEMCPY should be defined as 1 if you actually want to
345 have memset and memcpy called. People report that the macro
346 versions are often enough faster than libc versions on many
347 systems that it is better to use them.
348
349 */
350
351 #define HAVE_MEMCPY
352
353 #ifndef USE_MEMCPY
354 #ifdef HAVE_MEMCPY
355 #define USE_MEMCPY 1
356 #else
357 #define USE_MEMCPY 0
358 #endif
359 #endif
360
361 #if (__STD_C || defined(HAVE_MEMCPY))
362
363 #if __STD_C
364 void* memset(void*, int, size_t);
365 void* memcpy(void*, const void*, size_t);
366 #else
367 #ifdef WIN32
368 /* On Win32 platforms, 'memset()' and 'memcpy()' are already declared in */
369 /* 'windows.h' */
370 #else
371 Void_t* memset();
372 Void_t* memcpy();
373 #endif
374 #endif
375 #endif
376
377 #if USE_MEMCPY
378
379 /* The following macros are only invoked with (2n+1)-multiples of
380 INTERNAL_SIZE_T units, with a positive integer n. This is exploited
381 for fast inline execution when n is small. */
382
383 #define MALLOC_ZERO(charp, nbytes) \
384 do { \
385 INTERNAL_SIZE_T mzsz = (nbytes); \
386 if(mzsz <= 9*sizeof(mzsz)) { \
387 INTERNAL_SIZE_T* mz = (INTERNAL_SIZE_T*) (charp); \
388 if(mzsz >= 5*sizeof(mzsz)) { *mz++ = 0; \
389 *mz++ = 0; \
390 if(mzsz >= 7*sizeof(mzsz)) { *mz++ = 0; \
391 *mz++ = 0; \
392 if(mzsz >= 9*sizeof(mzsz)) { *mz++ = 0; \
393 *mz++ = 0; }}} \
394 *mz++ = 0; \
395 *mz++ = 0; \
396 *mz = 0; \
397 } else memset((charp), 0, mzsz); \
398 } while(0)
399
400 #define MALLOC_COPY(dest,src,nbytes) \
401 do { \
402 INTERNAL_SIZE_T mcsz = (nbytes); \
403 if(mcsz <= 9*sizeof(mcsz)) { \
404 INTERNAL_SIZE_T* mcsrc = (INTERNAL_SIZE_T*) (src); \
405 INTERNAL_SIZE_T* mcdst = (INTERNAL_SIZE_T*) (dest); \
406 if(mcsz >= 5*sizeof(mcsz)) { *mcdst++ = *mcsrc++; \
407 *mcdst++ = *mcsrc++; \
408 if(mcsz >= 7*sizeof(mcsz)) { *mcdst++ = *mcsrc++; \
409 *mcdst++ = *mcsrc++; \
410 if(mcsz >= 9*sizeof(mcsz)) { *mcdst++ = *mcsrc++; \
411 *mcdst++ = *mcsrc++; }}} \
412 *mcdst++ = *mcsrc++; \
413 *mcdst++ = *mcsrc++; \
414 *mcdst = *mcsrc ; \
415 } else memcpy(dest, src, mcsz); \
416 } while(0)
417
418 #else /* !USE_MEMCPY */
419
420 /* Use Duff's device for good zeroing/copying performance. */
421
422 #define MALLOC_ZERO(charp, nbytes) \
423 do { \
424 INTERNAL_SIZE_T* mzp = (INTERNAL_SIZE_T*)(charp); \
425 long mctmp = (nbytes)/sizeof(INTERNAL_SIZE_T), mcn; \
426 if (mctmp < 8) mcn = 0; else { mcn = (mctmp-1)/8; mctmp %= 8; } \
427 switch (mctmp) { \
428 case 0: for(;;) { *mzp++ = 0; \
429 case 7: *mzp++ = 0; \
430 case 6: *mzp++ = 0; \
431 case 5: *mzp++ = 0; \
432 case 4: *mzp++ = 0; \
433 case 3: *mzp++ = 0; \
434 case 2: *mzp++ = 0; \
435 case 1: *mzp++ = 0; if(mcn <= 0) break; mcn--; } \
436 } \
437 } while(0)
438
439 #define MALLOC_COPY(dest,src,nbytes) \
440 do { \
441 INTERNAL_SIZE_T* mcsrc = (INTERNAL_SIZE_T*) src; \
442 INTERNAL_SIZE_T* mcdst = (INTERNAL_SIZE_T*) dest; \
443 long mctmp = (nbytes)/sizeof(INTERNAL_SIZE_T), mcn; \
444 if (mctmp < 8) mcn = 0; else { mcn = (mctmp-1)/8; mctmp %= 8; } \
445 switch (mctmp) { \
446 case 0: for(;;) { *mcdst++ = *mcsrc++; \
447 case 7: *mcdst++ = *mcsrc++; \
448 case 6: *mcdst++ = *mcsrc++; \
449 case 5: *mcdst++ = *mcsrc++; \
450 case 4: *mcdst++ = *mcsrc++; \
451 case 3: *mcdst++ = *mcsrc++; \
452 case 2: *mcdst++ = *mcsrc++; \
453 case 1: *mcdst++ = *mcsrc++; if(mcn <= 0) break; mcn--; } \
454 } \
455 } while(0)
456
457 #endif
458
459
460 /*
461 Define HAVE_MMAP to optionally make malloc() use mmap() to
462 allocate very large blocks. These will be returned to the
463 operating system immediately after a free().
464 */
465
466 /***
467 #ifndef HAVE_MMAP
468 #define HAVE_MMAP 1
469 #endif
470 ***/
471 #undef HAVE_MMAP /* Not available for U-Boot */
472
473 /*
474 Define HAVE_MREMAP to make realloc() use mremap() to re-allocate
475 large blocks. This is currently only possible on Linux with
476 kernel versions newer than 1.3.77.
477 */
478
479 /***
480 #ifndef HAVE_MREMAP
481 #ifdef INTERNAL_LINUX_C_LIB
482 #define HAVE_MREMAP 1
483 #else
484 #define HAVE_MREMAP 0
485 #endif
486 #endif
487 ***/
488 #undef HAVE_MREMAP /* Not available for U-Boot */
489
490 #ifdef HAVE_MMAP
491
492 #include <unistd.h>
493 #include <fcntl.h>
494 #include <sys/mman.h>
495
496 #if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
497 #define MAP_ANONYMOUS MAP_ANON
498 #endif
499
500 #endif /* HAVE_MMAP */
501
502 /*
503 Access to system page size. To the extent possible, this malloc
504 manages memory from the system in page-size units.
505
506 The following mechanics for getpagesize were adapted from
507 bsd/gnu getpagesize.h
508 */
509
510 #define LACKS_UNISTD_H /* Shortcut for U-Boot */
511 #define malloc_getpagesize 4096
512
513 #ifndef LACKS_UNISTD_H
514 # include <unistd.h>
515 #endif
516
517 #ifndef malloc_getpagesize
518 # ifdef _SC_PAGESIZE /* some SVR4 systems omit an underscore */
519 # ifndef _SC_PAGE_SIZE
520 # define _SC_PAGE_SIZE _SC_PAGESIZE
521 # endif
522 # endif
523 # ifdef _SC_PAGE_SIZE
524 # define malloc_getpagesize sysconf(_SC_PAGE_SIZE)
525 # else
526 # if defined(BSD) || defined(DGUX) || defined(HAVE_GETPAGESIZE)
527 extern size_t getpagesize();
528 # define malloc_getpagesize getpagesize()
529 # else
530 # ifdef WIN32
531 # define malloc_getpagesize (4096) /* TBD: Use 'GetSystemInfo' instead */
532 # else
533 # ifndef LACKS_SYS_PARAM_H
534 # include <sys/param.h>
535 # endif
536 # ifdef EXEC_PAGESIZE
537 # define malloc_getpagesize EXEC_PAGESIZE
538 # else
539 # ifdef NBPG
540 # ifndef CLSIZE
541 # define malloc_getpagesize NBPG
542 # else
543 # define malloc_getpagesize (NBPG * CLSIZE)
544 # endif
545 # else
546 # ifdef NBPC
547 # define malloc_getpagesize NBPC
548 # else
549 # ifdef PAGESIZE
550 # define malloc_getpagesize PAGESIZE
551 # else
552 # define malloc_getpagesize (4096) /* just guess */
553 # endif
554 # endif
555 # endif
556 # endif
557 # endif
558 # endif
559 # endif
560 #endif
561
562
563 /*
564
565 This version of malloc supports the standard SVID/XPG mallinfo
566 routine that returns a struct containing the same kind of
567 information you can get from malloc_stats. It should work on
568 any SVID/XPG compliant system that has a /usr/include/malloc.h
569 defining struct mallinfo. (If you'd like to install such a thing
570 yourself, cut out the preliminary declarations as described above
571 and below and save them in a malloc.h file. But there's no
572 compelling reason to bother to do this.)
573
574 The main declaration needed is the mallinfo struct that is returned
575 (by-copy) by mallinfo(). The SVID/XPG malloinfo struct contains a
576 bunch of fields, most of which are not even meaningful in this
577 version of malloc. Some of these fields are are instead filled by
578 mallinfo() with other numbers that might possibly be of interest.
579
580 HAVE_USR_INCLUDE_MALLOC_H should be set if you have a
581 /usr/include/malloc.h file that includes a declaration of struct
582 mallinfo. If so, it is included; else an SVID2/XPG2 compliant
583 version is declared below. These must be precisely the same for
584 mallinfo() to work.
585
586 */
587
588 /* #define HAVE_USR_INCLUDE_MALLOC_H */
589
590 #ifdef HAVE_USR_INCLUDE_MALLOC_H
591 #include "/usr/include/malloc.h"
592 #else
593
594 /* SVID2/XPG mallinfo structure */
595
596 struct mallinfo {
597 int arena; /* total space allocated from system */
598 int ordblks; /* number of non-inuse chunks */
599 int smblks; /* unused -- always zero */
600 int hblks; /* number of mmapped regions */
601 int hblkhd; /* total space in mmapped regions */
602 int usmblks; /* unused -- always zero */
603 int fsmblks; /* unused -- always zero */
604 int uordblks; /* total allocated space */
605 int fordblks; /* total non-inuse space */
606 int keepcost; /* top-most, releasable (via malloc_trim) space */
607 };
608
609 /* SVID2/XPG mallopt options */
610
611 #define M_MXFAST 1 /* UNUSED in this malloc */
612 #define M_NLBLKS 2 /* UNUSED in this malloc */
613 #define M_GRAIN 3 /* UNUSED in this malloc */
614 #define M_KEEP 4 /* UNUSED in this malloc */
615
616 #endif
617
618 /* mallopt options that actually do something */
619
620 #define M_TRIM_THRESHOLD -1
621 #define M_TOP_PAD -2
622 #define M_MMAP_THRESHOLD -3
623 #define M_MMAP_MAX -4
624
625
626 #ifndef DEFAULT_TRIM_THRESHOLD
627 #define DEFAULT_TRIM_THRESHOLD (128 * 1024)
628 #endif
629
630 /*
631 M_TRIM_THRESHOLD is the maximum amount of unused top-most memory
632 to keep before releasing via malloc_trim in free().
633
634 Automatic trimming is mainly useful in long-lived programs.
635 Because trimming via sbrk can be slow on some systems, and can
636 sometimes be wasteful (in cases where programs immediately
637 afterward allocate more large chunks) the value should be high
638 enough so that your overall system performance would improve by
639 releasing.
640
641 The trim threshold and the mmap control parameters (see below)
642 can be traded off with one another. Trimming and mmapping are
643 two different ways of releasing unused memory back to the
644 system. Between these two, it is often possible to keep
645 system-level demands of a long-lived program down to a bare
646 minimum. For example, in one test suite of sessions measuring
647 the XF86 X server on Linux, using a trim threshold of 128K and a
648 mmap threshold of 192K led to near-minimal long term resource
649 consumption.
650
651 If you are using this malloc in a long-lived program, it should
652 pay to experiment with these values. As a rough guide, you
653 might set to a value close to the average size of a process
654 (program) running on your system. Releasing this much memory
655 would allow such a process to run in memory. Generally, it's
656 worth it to tune for trimming rather tham memory mapping when a
657 program undergoes phases where several large chunks are
658 allocated and released in ways that can reuse each other's
659 storage, perhaps mixed with phases where there are no such
660 chunks at all. And in well-behaved long-lived programs,
661 controlling release of large blocks via trimming versus mapping
662 is usually faster.
663
664 However, in most programs, these parameters serve mainly as
665 protection against the system-level effects of carrying around
666 massive amounts of unneeded memory. Since frequent calls to
667 sbrk, mmap, and munmap otherwise degrade performance, the default
668 parameters are set to relatively high values that serve only as
669 safeguards.
670
671 The default trim value is high enough to cause trimming only in
672 fairly extreme (by current memory consumption standards) cases.
673 It must be greater than page size to have any useful effect. To
674 disable trimming completely, you can set to (unsigned long)(-1);
675
676
677 */
678
679
680 #ifndef DEFAULT_TOP_PAD
681 #define DEFAULT_TOP_PAD (0)
682 #endif
683
684 /*
685 M_TOP_PAD is the amount of extra `padding' space to allocate or
686 retain whenever sbrk is called. It is used in two ways internally:
687
688 * When sbrk is called to extend the top of the arena to satisfy
689 a new malloc request, this much padding is added to the sbrk
690 request.
691
692 * When malloc_trim is called automatically from free(),
693 it is used as the `pad' argument.
694
695 In both cases, the actual amount of padding is rounded
696 so that the end of the arena is always a system page boundary.
697
698 The main reason for using padding is to avoid calling sbrk so
699 often. Having even a small pad greatly reduces the likelihood
700 that nearly every malloc request during program start-up (or
701 after trimming) will invoke sbrk, which needlessly wastes
702 time.
703
704 Automatic rounding-up to page-size units is normally sufficient
705 to avoid measurable overhead, so the default is 0. However, in
706 systems where sbrk is relatively slow, it can pay to increase
707 this value, at the expense of carrying around more memory than
708 the program needs.
709
710 */
711
712
713 #ifndef DEFAULT_MMAP_THRESHOLD
714 #define DEFAULT_MMAP_THRESHOLD (128 * 1024)
715 #endif
716
717 /*
718
719 M_MMAP_THRESHOLD is the request size threshold for using mmap()
720 to service a request. Requests of at least this size that cannot
721 be allocated using already-existing space will be serviced via mmap.
722 (If enough normal freed space already exists it is used instead.)
723
724 Using mmap segregates relatively large chunks of memory so that
725 they can be individually obtained and released from the host
726 system. A request serviced through mmap is never reused by any
727 other request (at least not directly; the system may just so
728 happen to remap successive requests to the same locations).
729
730 Segregating space in this way has the benefit that mmapped space
731 can ALWAYS be individually released back to the system, which
732 helps keep the system level memory demands of a long-lived
733 program low. Mapped memory can never become `locked' between
734 other chunks, as can happen with normally allocated chunks, which
735 menas that even trimming via malloc_trim would not release them.
736
737 However, it has the disadvantages that:
738
739 1. The space cannot be reclaimed, consolidated, and then
740 used to service later requests, as happens with normal chunks.
741 2. It can lead to more wastage because of mmap page alignment
742 requirements
743 3. It causes malloc performance to be more dependent on host
744 system memory management support routines which may vary in
745 implementation quality and may impose arbitrary
746 limitations. Generally, servicing a request via normal
747 malloc steps is faster than going through a system's mmap.
748
749 All together, these considerations should lead you to use mmap
750 only for relatively large requests.
751
752
753 */
754
755
756 #ifndef DEFAULT_MMAP_MAX
757 #ifdef HAVE_MMAP
758 #define DEFAULT_MMAP_MAX (64)
759 #else
760 #define DEFAULT_MMAP_MAX (0)
761 #endif
762 #endif
763
764 /*
765 M_MMAP_MAX is the maximum number of requests to simultaneously
766 service using mmap. This parameter exists because:
767
768 1. Some systems have a limited number of internal tables for
769 use by mmap.
770 2. In most systems, overreliance on mmap can degrade overall
771 performance.
772 3. If a program allocates many large regions, it is probably
773 better off using normal sbrk-based allocation routines that
774 can reclaim and reallocate normal heap memory. Using a
775 small value allows transition into this mode after the
776 first few allocations.
777
778 Setting to 0 disables all use of mmap. If HAVE_MMAP is not set,
779 the default value is 0, and attempts to set it to non-zero values
780 in mallopt will fail.
781 */
782
783
784 /*
785 USE_DL_PREFIX will prefix all public routines with the string 'dl'.
786 Useful to quickly avoid procedure declaration conflicts and linker
787 symbol conflicts with existing memory allocation routines.
788
789 */
790
791 /* #define USE_DL_PREFIX */
792
793
794 /*
795
796 Special defines for linux libc
797
798 Except when compiled using these special defines for Linux libc
799 using weak aliases, this malloc is NOT designed to work in
800 multithreaded applications. No semaphores or other concurrency
801 control are provided to ensure that multiple malloc or free calls
802 don't run at the same time, which could be disasterous. A single
803 semaphore could be used across malloc, realloc, and free (which is
804 essentially the effect of the linux weak alias approach). It would
805 be hard to obtain finer granularity.
806
807 */
808
809
810 #ifdef INTERNAL_LINUX_C_LIB
811
812 #if __STD_C
813
814 Void_t * __default_morecore_init (ptrdiff_t);
815 Void_t *(*__morecore)(ptrdiff_t) = __default_morecore_init;
816
817 #else
818
819 Void_t * __default_morecore_init ();
820 Void_t *(*__morecore)() = __default_morecore_init;
821
822 #endif
823
824 #define MORECORE (*__morecore)
825 #define MORECORE_FAILURE 0
826 #define MORECORE_CLEARS 1
827
828 #else /* INTERNAL_LINUX_C_LIB */
829
830 #if __STD_C
831 extern Void_t* sbrk(ptrdiff_t);
832 #else
833 extern Void_t* sbrk();
834 #endif
835
836 #ifndef MORECORE
837 #define MORECORE sbrk
838 #endif
839
840 #ifndef MORECORE_FAILURE
841 #define MORECORE_FAILURE -1
842 #endif
843
844 #ifndef MORECORE_CLEARS
845 #define MORECORE_CLEARS 1
846 #endif
847
848 #endif /* INTERNAL_LINUX_C_LIB */
849
850 #if defined(INTERNAL_LINUX_C_LIB) && defined(__ELF__)
851
852 #define cALLOc __libc_calloc
853 #define fREe __libc_free
854 #define mALLOc __libc_malloc
855 #define mEMALIGn __libc_memalign
856 #define rEALLOc __libc_realloc
857 #define vALLOc __libc_valloc
858 #define pvALLOc __libc_pvalloc
859 #define mALLINFo __libc_mallinfo
860 #define mALLOPt __libc_mallopt
861
862 #pragma weak calloc = __libc_calloc
863 #pragma weak free = __libc_free
864 #pragma weak cfree = __libc_free
865 #pragma weak malloc = __libc_malloc
866 #pragma weak memalign = __libc_memalign
867 #pragma weak realloc = __libc_realloc
868 #pragma weak valloc = __libc_valloc
869 #pragma weak pvalloc = __libc_pvalloc
870 #pragma weak mallinfo = __libc_mallinfo
871 #pragma weak mallopt = __libc_mallopt
872
873 #else
874
875 #if CONFIG_IS_ENABLED(SYS_MALLOC_SIMPLE)
876 #define malloc malloc_simple
877 #define realloc realloc_simple
878 #define memalign memalign_simple
free(void * ptr)879 static inline void free(void *ptr) {}
880 void *calloc(size_t nmemb, size_t size);
881 void *memalign_simple(size_t alignment, size_t bytes);
882 void *realloc_simple(void *ptr, size_t size);
883 void malloc_simple_info(void);
884 #else
885
886 # ifdef USE_DL_PREFIX
887 # define cALLOc dlcalloc
888 # define fREe dlfree
889 # define mALLOc dlmalloc
890 # define mEMALIGn dlmemalign
891 # define rEALLOc dlrealloc
892 # define vALLOc dlvalloc
893 # define pvALLOc dlpvalloc
894 # define mALLINFo dlmallinfo
895 # define mALLOPt dlmallopt
896 # else /* USE_DL_PREFIX */
897 # define cALLOc calloc
898 # define fREe free
899 # define mALLOc malloc
900 # define mEMALIGn memalign
901 # define rEALLOc realloc
902 # define vALLOc valloc
903 # define pvALLOc pvalloc
904 # define mALLINFo mallinfo
905 # define mALLOPt mallopt
906 # endif /* USE_DL_PREFIX */
907
908 #endif
909
910 /* Set up pre-relocation malloc() ready for use */
911 int initf_malloc(void);
912
913 /* Public routines */
914
915 /* Simple versions which can be used when space is tight */
916 void *malloc_simple(size_t size);
917
918 #pragma GCC visibility push(hidden)
919 # if __STD_C
920
921 Void_t* mALLOc(size_t);
922 void fREe(Void_t*);
923 Void_t* rEALLOc(Void_t*, size_t);
924 Void_t* mEMALIGn(size_t, size_t);
925 Void_t* vALLOc(size_t);
926 Void_t* pvALLOc(size_t);
927 Void_t* cALLOc(size_t, size_t);
928 void cfree(Void_t*);
929 int malloc_trim(size_t);
930 size_t malloc_usable_size(Void_t*);
931 void malloc_stats(void);
932 int mALLOPt(int, int);
933 struct mallinfo mALLINFo(void);
934 # else
935 Void_t* mALLOc();
936 void fREe();
937 Void_t* rEALLOc();
938 Void_t* mEMALIGn();
939 Void_t* vALLOc();
940 Void_t* pvALLOc();
941 Void_t* cALLOc();
942 void cfree();
943 int malloc_trim();
944 size_t malloc_usable_size();
945 void malloc_stats();
946 int mALLOPt();
947 struct mallinfo mALLINFo();
948 # endif
949 #endif
950 #pragma GCC visibility pop
951
952 /*
953 * Begin and End of memory area for malloc(), and current "brk"
954 */
955 extern ulong mem_malloc_start;
956 extern ulong mem_malloc_end;
957 extern ulong mem_malloc_brk;
958
959 void mem_malloc_init(ulong start, ulong size);
960
961 #ifdef __cplusplus
962 }; /* end of extern "C" */
963 #endif
964
965 #endif /* __MALLOC_H__ */
966