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malloc.c
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malloc.c
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/* malloc.c
*
*/
/*
* 'The Chamber of Records,' said Gimli. 'I guess that is where we now stand.'
*
* [p.321 of _The Lord of the Rings_, II/v: "The Bridge of Khazad-Dûm"]
*/
/* This file contains Perl's own implementation of the malloc library.
* It is used if Configure decides that, on your platform, Perl's
* version is better than the OS's, or if you give Configure the
* -Dusemymalloc command-line option.
*/
/*
Here are some notes on configuring Perl's malloc. (For non-perl
usage see below.)
There are two macros which serve as bulk disablers of advanced
features of this malloc: NO_FANCY_MALLOC, PLAIN_MALLOC (undef by
default). Look in the list of default values below to understand
their exact effect. Defining NO_FANCY_MALLOC returns malloc.c to the
state of the malloc in Perl 5.004. Additionally defining PLAIN_MALLOC
returns it to the state as of Perl 5.000.
Note that some of the settings below may be ignored in the code based
on values of other macros. The PERL_CORE symbol is only defined when
perl itself is being compiled (so malloc can make some assumptions
about perl's facilities being available to it).
Each config option has a short description, followed by its name,
default value, and a comment about the default (if applicable). Some
options take a precise value, while the others are just boolean.
The boolean ones are listed first.
# Read configuration settings from malloc_cfg.h
HAVE_MALLOC_CFG_H undef
# Enable code for an emergency memory pool in $^M. See perlvar.pod
# for a description of $^M.
PERL_EMERGENCY_SBRK (!PLAIN_MALLOC && (PERL_CORE || !NO_MALLOC_DYNAMIC_CFG))
# Enable code for printing memory statistics.
DEBUGGING_MSTATS (!PLAIN_MALLOC && PERL_CORE)
# Move allocation info for small buckets into separate areas.
# Memory optimization (especially for small allocations, of the
# less than 64 bytes). Since perl usually makes a large number
# of small allocations, this is usually a win.
PACK_MALLOC (!PLAIN_MALLOC && !RCHECK)
# Add one page to big powers of two when calculating bucket size.
# This is targeted at big allocations, as are common in image
# processing.
TWO_POT_OPTIMIZE !PLAIN_MALLOC
# Use intermediate bucket sizes between powers-of-two. This is
# generally a memory optimization, and a (small) speed pessimization.
BUCKETS_ROOT2 !NO_FANCY_MALLOC
# Do not check small deallocations for bad free(). Memory
# and speed optimization, error reporting pessimization.
IGNORE_SMALL_BAD_FREE (!NO_FANCY_MALLOC && !RCHECK)
# Use table lookup to decide in which bucket a given allocation will go.
SMALL_BUCKET_VIA_TABLE !NO_FANCY_MALLOC
# Use a perl-defined sbrk() instead of the (presumably broken or
# missing) system-supplied sbrk().
USE_PERL_SBRK undef
# Use system malloc() (or calloc() etc.) to emulate sbrk(). Normally
# only used with broken sbrk()s.
PERL_SBRK_VIA_MALLOC undef
# Which allocator to use if PERL_SBRK_VIA_MALLOC
SYSTEM_ALLOC(a) malloc(a)
# Minimal alignment (in bytes, should be a power of 2) of SYSTEM_ALLOC
SYSTEM_ALLOC_ALIGNMENT MEM_ALIGNBYTES
# Disable memory overwrite checking with DEBUGGING. Memory and speed
# optimization, error reporting pessimization.
NO_RCHECK undef
# Enable memory overwrite checking with DEBUGGING. Memory and speed
# pessimization, error reporting optimization
RCHECK (DEBUGGING && !NO_RCHECK)
# Do not overwrite uninit areas with DEBUGGING. Speed
# optimization, error reporting pessimization
NO_MFILL undef
# Overwrite uninit areas with DEBUGGING. Speed
# pessimization, error reporting optimization
MALLOC_FILL (DEBUGGING && !NO_RCHECK && !NO_MFILL)
# Do not check overwritten uninit areas with DEBUGGING. Speed
# optimization, error reporting pessimization
NO_FILL_CHECK undef
# Check overwritten uninit areas with DEBUGGING. Speed
# pessimization, error reporting optimization
MALLOC_FILL_CHECK (DEBUGGING && !NO_RCHECK && !NO_FILL_CHECK)
# Failed allocations bigger than this size croak (if
# PERL_EMERGENCY_SBRK is enabled) without touching $^M. See
# perlvar.pod for a description of $^M.
BIG_SIZE (1<<16) # 64K
# Starting from this power of two, add an extra page to the
# size of the bucket. This enables optimized allocations of sizes
# close to powers of 2. Note that the value is indexed at 0.
FIRST_BIG_POW2 15 # 32K, 16K is used too often
# Estimate of minimal memory footprint. malloc uses this value to
# request the most reasonable largest blocks of memory from the system.
FIRST_SBRK (48*1024)
# Round up sbrk()s to multiples of this.
MIN_SBRK 2048
# Round up sbrk()s to multiples of this percent of footprint.
MIN_SBRK_FRAC 3
# Round up sbrk()s to multiples of this multiple of 1/1000 of footprint.
MIN_SBRK_FRAC1000 (10 * MIN_SBRK_FRAC)
# Add this much memory to big powers of two to get the bucket size.
PERL_PAGESIZE 4096
# This many sbrk() discontinuities should be tolerated even
# from the start without deciding that sbrk() is usually
# discontinuous.
SBRK_ALLOW_FAILURES 3
# This many continuous sbrk()s compensate for one discontinuous one.
SBRK_FAILURE_PRICE 50
# Some configurations may ask for 12-byte-or-so allocations which
# require 8-byte alignment (?!). In such situation one needs to
# define this to disable 12-byte bucket (will increase memory footprint)
STRICT_ALIGNMENT undef
# Do not allow configuration of runtime options at runtime
NO_MALLOC_DYNAMIC_CFG undef
# Do not allow configuration of runtime options via $ENV{PERL_MALLOC_OPT}
NO_PERL_MALLOC_ENV undef
[The variable consists of ;-separated parts of the form CODE=VALUE
with 1-character codes F, M, f, A, P, G, d, a, c for runtime
configuration of FIRST_SBRK, MIN_SBRK, MIN_SBRK_FRAC1000,
SBRK_ALLOW_FAILURES, SBRK_FAILURE_PRICE, sbrk_goodness,
filldead, fillalive, fillcheck. The last 3 are for DEBUGGING
build, and allow switching the tests for free()ed memory read,
uninit memory reads, and free()ed memory write.]
This implementation assumes that calling PerlIO_printf() does not
result in any memory allocation calls (used during a panic).
*/
/*
If used outside of Perl environment, it may be useful to redefine
the following macros (listed below with defaults):
# Type of address returned by allocation functions
Malloc_t void *
# Type of size argument for allocation functions
MEM_SIZE unsigned long
# size of void*
PTRSIZE 4
# Maximal value in LONG
LONG_MAX 0x7FFFFFFF
# Unsigned integer type big enough to keep a pointer
UV unsigned long
# Signed integer of the same sizeof() as UV
IV long
# Type of pointer with 1-byte granularity
caddr_t char *
# Type returned by free()
Free_t void
# Conversion of pointer to integer
PTR2UV(ptr) ((UV)(ptr))
# Conversion of integer to pointer
INT2PTR(type, i) ((type)(i))
# printf()-%-Conversion of UV to pointer
UVuf "lu"
# printf()-%-Conversion of UV to hex pointer
UVxf "lx"
# Alignment to use
MEM_ALIGNBYTES 4
# Very fatal condition reporting function (cannot call any )
fatalcroak(arg) write(2,arg,strlen(arg)) + exit(2)
# Fatal error reporting function
croak(format, arg) warn(idem) + exit(1)
# Fatal error reporting function
croak2(format, arg1, arg2) warn2(idem) + exit(1)
# Error reporting function
warn(format, arg) fprintf(stderr, idem)
# Error reporting function
warn2(format, arg1, arg2) fprintf(stderr, idem)
# Locking/unlocking for MT operation
MALLOC_LOCK MUTEX_LOCK(&PL_malloc_mutex)
MALLOC_UNLOCK MUTEX_UNLOCK(&PL_malloc_mutex)
# Locking/unlocking mutex for MT operation
MUTEX_LOCK(l) void
MUTEX_UNLOCK(l) void
*/
#ifdef HAVE_MALLOC_CFG_H
# include "malloc_cfg.h"
#endif
#ifndef NO_FANCY_MALLOC
# ifndef SMALL_BUCKET_VIA_TABLE
# define SMALL_BUCKET_VIA_TABLE
# endif
# ifndef BUCKETS_ROOT2
# define BUCKETS_ROOT2
# endif
# ifndef IGNORE_SMALL_BAD_FREE
# define IGNORE_SMALL_BAD_FREE
# endif
#endif
#ifndef PLAIN_MALLOC /* Bulk enable features */
# ifndef PACK_MALLOC
# define PACK_MALLOC
# endif
# ifndef TWO_POT_OPTIMIZE
# define TWO_POT_OPTIMIZE
# endif
# if (defined(PERL_CORE) || !defined(NO_MALLOC_DYNAMIC_CFG)) && !defined(PERL_EMERGENCY_SBRK)
# define PERL_EMERGENCY_SBRK
# endif
# if defined(PERL_CORE) && !defined(DEBUGGING_MSTATS)
# define DEBUGGING_MSTATS
# endif
#endif
#define MIN_BUC_POW2 (sizeof(void*) > 4 ? 3 : 2) /* Allow for 4-byte arena. */
#define MIN_BUCKET (MIN_BUC_POW2 * BUCKETS_PER_POW2)
#if !(defined(I286) || defined(atarist))
/* take 2k unless the block is bigger than that */
# define LOG_OF_MIN_ARENA 11
#else
/* take 16k unless the block is bigger than that
(80286s like large segments!), probably good on the atari too */
# define LOG_OF_MIN_ARENA 14
#endif
#if defined(DEBUGGING) && !defined(NO_RCHECK)
# define RCHECK
#endif
#if defined(DEBUGGING) && !defined(NO_RCHECK) && !defined(NO_MFILL) && !defined(MALLOC_FILL)
# define MALLOC_FILL
#endif
#if defined(DEBUGGING) && !defined(NO_RCHECK) && !defined(NO_FILL_CHECK) && !defined(MALLOC_FILL_CHECK)
# define MALLOC_FILL_CHECK
#endif
#if defined(RCHECK) && defined(IGNORE_SMALL_BAD_FREE)
# undef IGNORE_SMALL_BAD_FREE
#endif
/*
* malloc.c (Caltech) 2/21/82
* Chris Kingsley, kingsley@cit-20.
*
* This is a very fast storage allocator. It allocates blocks of a small
* number of different sizes, and keeps free lists of each size. Blocks that
* don't exactly fit are passed up to the next larger size. In this
* implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long.
* If PACK_MALLOC is defined, small blocks are 2^n bytes long.
* This is designed for use in a program that uses vast quantities of memory,
* but bombs when it runs out.
*
* Modifications Copyright Ilya Zakharevich 1996-99.
*
* Still very quick, but much more thrifty. (Std config is 10% slower
* than it was, and takes 67% of old heap size for typical usage.)
*
* Allocations of small blocks are now table-driven to many different
* buckets. Sizes of really big buckets are increased to accomodata
* common size=power-of-2 blocks. Running-out-of-memory is made into
* an exception. Deeply configurable and thread-safe.
*
*/
#ifdef PERL_CORE
# include "EXTERN.h"
# define PERL_IN_MALLOC_C
# include "perl.h"
# define PERL_MAYBE_ALIVE 1
#else
# include <stdlib.h>
# include <stdio.h>
# include <memory.h>
# ifdef OS2
# include <io.h>
# endif
# include <string.h>
# ifndef Malloc_t
# define Malloc_t void *
# endif
# ifndef PTRSIZE
# define PTRSIZE 4
# endif
# ifndef MEM_SIZE
# define MEM_SIZE unsigned long
# endif
# ifndef LONG_MAX
# define LONG_MAX 0x7FFFFFFF
# endif
# ifndef UV
# define UV unsigned long
# endif
# ifndef IV
# define IV long
# endif
# ifndef caddr_t
# define caddr_t char *
# endif
# ifndef Free_t
# define Free_t void
# endif
# define Copy(s,d,n,t) (void)memcpy((char*)(d),(char*)(s), (n) * sizeof(t))
# define CopyD(s,d,n,t) memcpy((char*)(d),(char*)(s), (n) * sizeof(t))
# define PerlEnv_getenv getenv
# define PerlIO_printf fprintf
# define PerlIO_stderr() stderr
# define PerlIO_puts(f,s) fputs(s,f)
# ifndef INT2PTR
# define INT2PTR(t,i) ((t)(i))
# endif
# ifndef PTR2UV
# define PTR2UV(p) ((UV)(p))
# endif
# ifndef UVuf
# define UVuf "lu"
# endif
# ifndef UVxf
# define UVxf "lx"
# endif
# ifndef MEM_ALIGNBYTES
# define MEM_ALIGNBYTES 4
# endif
# ifdef DEBUG_m
# undef DEBUG_m
# endif
# define DEBUG_m(a)
# ifdef DEBUGGING
# undef DEBUGGING
# endif
# ifndef pTHX
# define pTHX void
# define pTHX_
# ifdef HASATTRIBUTE_UNUSED
# define dTHX extern int Perl___notused PERL_UNUSED_DECL
# else
# define dTHX extern int Perl___notused
# endif
# define WITH_THX(s) s
# endif
# ifndef PERL_GET_INTERP
# define PERL_GET_INTERP PL_curinterp
# endif
# define PERL_MAYBE_ALIVE 1
# ifndef Perl_malloc
# define Perl_malloc malloc
# endif
# ifndef Perl_mfree
# define Perl_mfree free
# endif
# ifndef Perl_realloc
# define Perl_realloc realloc
# endif
# ifndef Perl_calloc
# define Perl_calloc calloc
# endif
# ifndef Perl_strdup
# define Perl_strdup strdup
# endif
#endif /* defined PERL_CORE */
#ifndef MUTEX_LOCK
# define MUTEX_LOCK(l)
#endif
#ifndef MUTEX_UNLOCK
# define MUTEX_UNLOCK(l)
#endif
#ifndef MALLOC_LOCK
# define MALLOC_LOCK MUTEX_LOCK(&PL_malloc_mutex)
#endif
#ifndef MALLOC_UNLOCK
# define MALLOC_UNLOCK MUTEX_UNLOCK(&PL_malloc_mutex)
#endif
# ifndef fatalcroak /* make depend */
# define fatalcroak(mess) (write(2, (mess), strlen(mess)), exit(2))
# endif
#ifdef DEBUGGING
# undef DEBUG_m
# define DEBUG_m(a) \
STMT_START { \
if (PERL_MAYBE_ALIVE && PERL_GET_THX) { \
dTHX; \
if (DEBUG_m_TEST) { \
PL_debug &= ~DEBUG_m_FLAG; \
a; \
PL_debug |= DEBUG_m_FLAG; \
} \
} \
} STMT_END
#endif
#ifdef PERL_IMPLICIT_CONTEXT
# define PERL_IS_ALIVE aTHX
#else
# define PERL_IS_ALIVE TRUE
#endif
/*
* Layout of memory:
* ~~~~~~~~~~~~~~~~
* The memory is broken into "blocks" which occupy multiples of 2K (and
* generally speaking, have size "close" to a power of 2). The addresses
* of such *unused* blocks are kept in nextf[i] with big enough i. (nextf
* is an array of linked lists.) (Addresses of used blocks are not known.)
*
* Moreover, since the algorithm may try to "bite" smaller blocks out
* of unused bigger ones, there are also regions of "irregular" size,
* managed separately, by a linked list chunk_chain.
*
* The third type of storage is the sbrk()ed-but-not-yet-used space, its
* end and size are kept in last_sbrk_top and sbrked_remains.
*
* Growing blocks "in place":
* ~~~~~~~~~~~~~~~~~~~~~~~~~
* The address of the block with the greatest address is kept in last_op
* (if not known, last_op is 0). If it is known that the memory above
* last_op is not continuous, or contains a chunk from chunk_chain,
* last_op is set to 0.
*
* The chunk with address last_op may be grown by expanding into
* sbrk()ed-but-not-yet-used space, or trying to sbrk() more continuous
* memory.
*
* Management of last_op:
* ~~~~~~~~~~~~~~~~~~~~~
*
* free() never changes the boundaries of blocks, so is not relevant.
*
* The only way realloc() may change the boundaries of blocks is if it
* grows a block "in place". However, in the case of success such a
* chunk is automatically last_op, and it remains last_op. In the case
* of failure getpages_adjacent() clears last_op.
*
* malloc() may change blocks by calling morecore() only.
*
* morecore() may create new blocks by:
* a) biting pieces from chunk_chain (cannot create one above last_op);
* b) biting a piece from an unused block (if block was last_op, this
* may create a chunk from chain above last_op, thus last_op is
* invalidated in such a case).
* c) biting of sbrk()ed-but-not-yet-used space. This creates
* a block which is last_op.
* d) Allocating new pages by calling getpages();
*
* getpages() creates a new block. It marks last_op at the bottom of
* the chunk of memory it returns.
*
* Active pages footprint:
* ~~~~~~~~~~~~~~~~~~~~~~
* Note that we do not need to traverse the lists in nextf[i], just take
* the first element of this list. However, we *need* to traverse the
* list in chunk_chain, but most the time it should be a very short one,
* so we do not step on a lot of pages we are not going to use.
*
* Flaws:
* ~~~~~
* get_from_bigger_buckets(): forget to increment price => Quite
* aggressive.
*/
/* I don't much care whether these are defined in sys/types.h--LAW */
#define u_char unsigned char
#define u_int unsigned int
/*
* I removed the definition of u_bigint which appeared to be u_bigint = UV
* u_bigint was only used in TWOK_MASKED and TWOK_SHIFT
* where I have used PTR2UV. RMB
*/
#define u_short unsigned short
/* 286 and atarist like big chunks, which gives too much overhead. */
#if (defined(RCHECK) || defined(I286) || defined(atarist)) && defined(PACK_MALLOC)
# undef PACK_MALLOC
#endif
/*
* The description below is applicable if PACK_MALLOC is not defined.
*
* The overhead on a block is at least 4 bytes. When free, this space
* contains a pointer to the next free block, and the bottom two bits must
* be zero. When in use, the first byte is set to MAGIC, and the second
* byte is the size index. The remaining bytes are for alignment.
* If range checking is enabled and the size of the block fits
* in two bytes, then the top two bytes hold the size of the requested block
* plus the range checking words, and the header word MINUS ONE.
*/
union overhead {
union overhead *ov_next; /* when free */
#if MEM_ALIGNBYTES > 4
double strut; /* alignment problems */
# if MEM_ALIGNBYTES > 8
char sstrut[MEM_ALIGNBYTES]; /* for the sizing */
# endif
#endif
struct {
/*
* Keep the ovu_index and ovu_magic in this order, having a char
* field first gives alignment indigestion in some systems, such as
* MachTen.
*/
u_char ovu_index; /* bucket # */
u_char ovu_magic; /* magic number */
#ifdef RCHECK
/* Subtract one to fit into u_short for an extra bucket */
u_short ovu_size; /* block size (requested + overhead - 1) */
u_int ovu_rmagic; /* range magic number */
#endif
} ovu;
#define ov_magic ovu.ovu_magic
#define ov_index ovu.ovu_index
#define ov_size ovu.ovu_size
#define ov_rmagic ovu.ovu_rmagic
};
#define MAGIC 0xff /* magic # on accounting info */
#define RMAGIC 0x55555555 /* magic # on range info */
#define RMAGIC_C 0x55 /* magic # on range info */
#ifdef RCHECK
# define RMAGIC_SZ sizeof (u_int) /* Overhead at end of bucket */
# ifdef TWO_POT_OPTIMIZE
# define MAX_SHORT_BUCKET (12 * BUCKETS_PER_POW2) /* size-1 fits in short */
# else
# define MAX_SHORT_BUCKET (13 * BUCKETS_PER_POW2)
# endif
#else
# define RMAGIC_SZ 0
#endif
#if !defined(PACK_MALLOC) && defined(BUCKETS_ROOT2)
# undef BUCKETS_ROOT2
#endif
#ifdef BUCKETS_ROOT2
# define BUCKET_TABLE_SHIFT 2
# define BUCKET_POW2_SHIFT 1
# define BUCKETS_PER_POW2 2
#else
# define BUCKET_TABLE_SHIFT MIN_BUC_POW2
# define BUCKET_POW2_SHIFT 0
# define BUCKETS_PER_POW2 1
#endif
#if !defined(MEM_ALIGNBYTES) || ((MEM_ALIGNBYTES > 4) && !defined(STRICT_ALIGNMENT))
/* Figure out the alignment of void*. */
struct aligner {
char c;
void *p;
};
# define ALIGN_SMALL ((int)((caddr_t)&(((struct aligner*)0)->p)))
#else
# define ALIGN_SMALL MEM_ALIGNBYTES
#endif
#define IF_ALIGN_8(yes,no) ((ALIGN_SMALL>4) ? (yes) : (no))
#ifdef BUCKETS_ROOT2
# define MAX_BUCKET_BY_TABLE 13
static const u_short buck_size[MAX_BUCKET_BY_TABLE + 1] =
{
0, 0, 0, 0, 4, 4, 8, 12, 16, 24, 32, 48, 64, 80,
};
# define BUCKET_SIZE_NO_SURPLUS(i) ((i) % 2 ? buck_size[i] : (1 << ((i) >> BUCKET_POW2_SHIFT)))
# define BUCKET_SIZE_REAL(i) ((i) <= MAX_BUCKET_BY_TABLE \
? buck_size[i] \
: ((1 << ((i) >> BUCKET_POW2_SHIFT)) \
- MEM_OVERHEAD(i) \
+ POW2_OPTIMIZE_SURPLUS(i)))
#else
# define BUCKET_SIZE_NO_SURPLUS(i) (1 << ((i) >> BUCKET_POW2_SHIFT))
# define BUCKET_SIZE(i) (BUCKET_SIZE_NO_SURPLUS(i) + POW2_OPTIMIZE_SURPLUS(i))
# define BUCKET_SIZE_REAL(i) (BUCKET_SIZE(i) - MEM_OVERHEAD(i))
#endif
#ifdef PACK_MALLOC
/* In this case there are several possible layout of arenas depending
* on the size. Arenas are of sizes multiple to 2K, 2K-aligned, and
* have a size close to a power of 2.
*
* Arenas of the size >= 4K keep one chunk only. Arenas of size 2K
* may keep one chunk or multiple chunks. Here are the possible
* layouts of arenas:
*
* # One chunk only, chunksize 2^k + SOMETHING - ALIGN, k >= 11
*
* INDEX MAGIC1 UNUSED CHUNK1
*
* # Multichunk with sanity checking and chunksize 2^k-ALIGN, k>7
*
* INDEX MAGIC1 MAGIC2 MAGIC3 UNUSED CHUNK1 CHUNK2 CHUNK3 ...
*
* # Multichunk with sanity checking and size 2^k-ALIGN, k=7
*
* INDEX MAGIC1 MAGIC2 MAGIC3 UNUSED CHUNK1 UNUSED CHUNK2 CHUNK3 ...
*
* # Multichunk with sanity checking and size up to 80
*
* INDEX UNUSED MAGIC1 UNUSED MAGIC2 UNUSED ... CHUNK1 CHUNK2 CHUNK3 ...
*
* # No sanity check (usually up to 48=byte-long buckets)
* INDEX UNUSED CHUNK1 CHUNK2 ...
*
* Above INDEX and MAGIC are one-byte-long. Sizes of UNUSED are
* appropriate to keep algorithms simple and memory aligned. INDEX
* encodes the size of the chunk, while MAGICn encodes state (used,
* free or non-managed-by-us-so-it-indicates-a-bug) of CHUNKn. MAGIC
* is used for sanity checking purposes only. SOMETHING is 0 or 4K
* (to make size of big CHUNK accomodate allocations for powers of two
* better).
*
* [There is no need to alignment between chunks, since C rules ensure
* that structs which need 2^k alignment have sizeof which is
* divisible by 2^k. Thus as far as the last chunk is aligned at the
* end of the arena, and 2K-alignment does not contradict things,
* everything is going to be OK for sizes of chunks 2^n and 2^n +
* 2^k. Say, 80-bit buckets will be 16-bit aligned, and as far as we
* put allocations for requests in 65..80 range, all is fine.
*
* Note, however, that standard malloc() puts more strict
* requirements than the above C rules. Moreover, our algorithms of
* realloc() may break this idyll, but we suppose that realloc() does
* need not change alignment.]
*
* Is very important to make calculation of the offset of MAGICm as
* quick as possible, since it is done on each malloc()/free(). In
* fact it is so quick that it has quite little effect on the speed of
* doing malloc()/free(). [By default] We forego such calculations
* for small chunks, but only to save extra 3% of memory, not because
* of speed considerations.
*
* Here is the algorithm [which is the same for all the allocations
* schemes above], see OV_MAGIC(block,bucket). Let OFFSETm be the
* offset of the CHUNKm from the start of ARENA. Then offset of
* MAGICm is (OFFSET1 >> SHIFT) + ADDOFFSET. Here SHIFT and ADDOFFSET
* are numbers which depend on the size of the chunks only.
*
* Let as check some sanity conditions. Numbers OFFSETm>>SHIFT are
* different for all the chunks in the arena if 2^SHIFT is not greater
* than size of the chunks in the arena. MAGIC1 will not overwrite
* INDEX provided ADDOFFSET is >0 if OFFSET1 < 2^SHIFT. MAGIClast
* will not overwrite CHUNK1 if OFFSET1 > (OFFSETlast >> SHIFT) +
* ADDOFFSET.
*
* Make SHIFT the maximal possible (there is no point in making it
* smaller). Since OFFSETlast is 2K - CHUNKSIZE, above restrictions
* give restrictions on OFFSET1 and on ADDOFFSET.
*
* In particular, for chunks of size 2^k with k>=6 we can put
* ADDOFFSET to be from 0 to 2^k - 2^(11-k), and have
* OFFSET1==chunksize. For chunks of size 80 OFFSET1 of 2K%80=48 is
* large enough to have ADDOFFSET between 1 and 16 (similarly for 96,
* when ADDOFFSET should be 1). In particular, keeping MAGICs for
* these sizes gives no additional size penalty.
*
* However, for chunks of size 2^k with k<=5 this gives OFFSET1 >=
* ADDOFSET + 2^(11-k). Keeping ADDOFFSET 0 allows for 2^(11-k)-2^(11-2k)
* chunks per arena. This is smaller than 2^(11-k) - 1 which are
* needed if no MAGIC is kept. [In fact, having a negative ADDOFFSET
* would allow for slightly more buckets per arena for k=2,3.]
*
* Similarly, for chunks of size 3/2*2^k with k<=5 MAGICs would span
* the area up to 2^(11-k)+ADDOFFSET. For k=4 this give optimal
* ADDOFFSET as -7..0. For k=3 ADDOFFSET can go up to 4 (with tiny
* savings for negative ADDOFFSET). For k=5 ADDOFFSET can go -1..16
* (with no savings for negative values).
*
* In particular, keeping ADDOFFSET 0 for sizes of chunks up to 2^6
* leads to tiny pessimizations in case of sizes 4, 8, 12, 24, and
* leads to no contradictions except for size=80 (or 96.)
*
* However, it also makes sense to keep no magic for sizes 48 or less.
* This is what we do. In this case one needs ADDOFFSET>=1 also for
* chunksizes 12, 24, and 48, unless one gets one less chunk per
* arena.
*
* The algo of OV_MAGIC(block,bucket) keeps ADDOFFSET 0 until
* chunksize of 64, then makes it 1.
*
* This allows for an additional optimization: the above scheme leads
* to giant overheads for sizes 128 or more (one whole chunk needs to
* be sacrifised to keep INDEX). Instead we use chunks not of size
* 2^k, but of size 2^k-ALIGN. If we pack these chunks at the end of
* the arena, then the beginnings are still in different 2^k-long
* sections of the arena if k>=7 for ALIGN==4, and k>=8 if ALIGN=8.
* Thus for k>7 the above algo of calculating the offset of the magic
* will still give different answers for different chunks. And to
* avoid the overrun of MAGIC1 into INDEX, one needs ADDOFFSET of >=1.
* In the case k=7 we just move the first chunk an extra ALIGN
* backward inside the ARENA (this is done once per arena lifetime,
* thus is not a big overhead). */
# define MAX_PACKED_POW2 6
# define MAX_PACKED (MAX_PACKED_POW2 * BUCKETS_PER_POW2 + BUCKET_POW2_SHIFT)
# define MAX_POW2_ALGO ((1<<(MAX_PACKED_POW2 + 1)) - M_OVERHEAD)
# define TWOK_MASK ((1<<LOG_OF_MIN_ARENA) - 1)
# define TWOK_MASKED(x) (PTR2UV(x) & ~TWOK_MASK)
# define TWOK_SHIFT(x) (PTR2UV(x) & TWOK_MASK)
# define OV_INDEXp(block) (INT2PTR(u_char*,TWOK_MASKED(block)))
# define OV_INDEX(block) (*OV_INDEXp(block))
# define OV_MAGIC(block,bucket) (*(OV_INDEXp(block) + \
(TWOK_SHIFT(block)>> \
(bucket>>BUCKET_POW2_SHIFT)) + \
(bucket >= MIN_NEEDS_SHIFT ? 1 : 0)))
/* A bucket can have a shift smaller than it size, we need to
shift its magic number so it will not overwrite index: */
# ifdef BUCKETS_ROOT2
# define MIN_NEEDS_SHIFT (7*BUCKETS_PER_POW2 - 1) /* Shift 80 greater than chunk 64. */
# else
# define MIN_NEEDS_SHIFT (7*BUCKETS_PER_POW2) /* Shift 128 greater than chunk 32. */
# endif
# define CHUNK_SHIFT 0
/* Number of active buckets of given ordinal. */
#ifdef IGNORE_SMALL_BAD_FREE
#define FIRST_BUCKET_WITH_CHECK (6 * BUCKETS_PER_POW2) /* 64 */
# define N_BLKS(bucket) ( (bucket) < FIRST_BUCKET_WITH_CHECK \
? ((1<<LOG_OF_MIN_ARENA) - 1)/BUCKET_SIZE_NO_SURPLUS(bucket) \
: n_blks[bucket] )
#else
# define N_BLKS(bucket) n_blks[bucket]
#endif
static const u_short n_blks[LOG_OF_MIN_ARENA * BUCKETS_PER_POW2] =
{
# if BUCKETS_PER_POW2==1
0, 0,
(MIN_BUC_POW2==2 ? 384 : 0),
224, 120, 62, 31, 16, 8, 4, 2
# else
0, 0, 0, 0,
(MIN_BUC_POW2==2 ? 384 : 0), (MIN_BUC_POW2==2 ? 384 : 0), /* 4, 4 */
224, 149, 120, 80, 62, 41, 31, 25, 16, 16, 8, 8, 4, 4, 2, 2
# endif
};
/* Shift of the first bucket with the given ordinal inside 2K chunk. */
#ifdef IGNORE_SMALL_BAD_FREE
# define BLK_SHIFT(bucket) ( (bucket) < FIRST_BUCKET_WITH_CHECK \
? ((1<<LOG_OF_MIN_ARENA) \
- BUCKET_SIZE_NO_SURPLUS(bucket) * N_BLKS(bucket)) \
: blk_shift[bucket])
#else
# define BLK_SHIFT(bucket) blk_shift[bucket]
#endif
static const u_short blk_shift[LOG_OF_MIN_ARENA * BUCKETS_PER_POW2] =
{
# if BUCKETS_PER_POW2==1
0, 0,
(MIN_BUC_POW2==2 ? 512 : 0),
256, 128, 64, 64, /* 8 to 64 */
16*sizeof(union overhead),
8*sizeof(union overhead),
4*sizeof(union overhead),
2*sizeof(union overhead),
# else
0, 0, 0, 0,
(MIN_BUC_POW2==2 ? 512 : 0), (MIN_BUC_POW2==2 ? 512 : 0),
256, 260, 128, 128, 64, 80, 64, 48, /* 8 to 96 */
16*sizeof(union overhead), 16*sizeof(union overhead),
8*sizeof(union overhead), 8*sizeof(union overhead),
4*sizeof(union overhead), 4*sizeof(union overhead),
2*sizeof(union overhead), 2*sizeof(union overhead),
# endif
};
# define NEEDED_ALIGNMENT 0x800 /* 2k boundaries */
# define WANTED_ALIGNMENT 0x800 /* 2k boundaries */
#else /* !PACK_MALLOC */
# define OV_MAGIC(block,bucket) (block)->ov_magic
# define OV_INDEX(block) (block)->ov_index
# define CHUNK_SHIFT 1
# define MAX_PACKED -1
# define NEEDED_ALIGNMENT MEM_ALIGNBYTES
# define WANTED_ALIGNMENT 0x400 /* 1k boundaries */
#endif /* !PACK_MALLOC */
#define M_OVERHEAD (sizeof(union overhead) + RMAGIC_SZ) /* overhead at start+end */
#ifdef PACK_MALLOC
# define MEM_OVERHEAD(bucket) \
(bucket <= MAX_PACKED ? 0 : M_OVERHEAD)
# ifdef SMALL_BUCKET_VIA_TABLE
# define START_SHIFTS_BUCKET ((MAX_PACKED_POW2 + 1) * BUCKETS_PER_POW2)
# define START_SHIFT MAX_PACKED_POW2
# ifdef BUCKETS_ROOT2 /* Chunks of size 3*2^n. */
# define SIZE_TABLE_MAX 80
# else
# define SIZE_TABLE_MAX 64
# endif
static const char bucket_of[] =
{
# ifdef BUCKETS_ROOT2 /* Chunks of size 3*2^n. */
/* 0 to 15 in 4-byte increments. */
(sizeof(void*) > 4 ? 6 : 5), /* 4/8, 5-th bucket for better reports */
6, /* 8 */
IF_ALIGN_8(8,7), 8, /* 16/12, 16 */
9, 9, 10, 10, /* 24, 32 */
11, 11, 11, 11, /* 48 */
12, 12, 12, 12, /* 64 */
13, 13, 13, 13, /* 80 */
13, 13, 13, 13 /* 80 */
# else /* !BUCKETS_ROOT2 */
/* 0 to 15 in 4-byte increments. */
(sizeof(void*) > 4 ? 3 : 2),
3,
4, 4,
5, 5, 5, 5,
6, 6, 6, 6,
6, 6, 6, 6
# endif /* !BUCKETS_ROOT2 */
};
# else /* !SMALL_BUCKET_VIA_TABLE */
# define START_SHIFTS_BUCKET MIN_BUCKET
# define START_SHIFT (MIN_BUC_POW2 - 1)
# endif /* !SMALL_BUCKET_VIA_TABLE */
#else /* !PACK_MALLOC */
# define MEM_OVERHEAD(bucket) M_OVERHEAD
# ifdef SMALL_BUCKET_VIA_TABLE
# undef SMALL_BUCKET_VIA_TABLE
# endif
# define START_SHIFTS_BUCKET MIN_BUCKET
# define START_SHIFT (MIN_BUC_POW2 - 1)
#endif /* !PACK_MALLOC */
/*
* Big allocations are often of the size 2^n bytes. To make them a
* little bit better, make blocks of size 2^n+pagesize for big n.
*/
#ifdef TWO_POT_OPTIMIZE
# ifndef PERL_PAGESIZE
# define PERL_PAGESIZE 4096
# endif
# ifndef FIRST_BIG_POW2
# define FIRST_BIG_POW2 15 /* 32K, 16K is used too often. */
# endif
# define FIRST_BIG_BLOCK (1<<FIRST_BIG_POW2)
/* If this value or more, check against bigger blocks. */
# define FIRST_BIG_BOUND (FIRST_BIG_BLOCK - M_OVERHEAD)
/* If less than this value, goes into 2^n-overhead-block. */
# define LAST_SMALL_BOUND ((FIRST_BIG_BLOCK>>1) - M_OVERHEAD)
# define POW2_OPTIMIZE_ADJUST(nbytes) \
((nbytes >= FIRST_BIG_BOUND) ? nbytes -= PERL_PAGESIZE : 0)
# define POW2_OPTIMIZE_SURPLUS(bucket) \
((bucket >= FIRST_BIG_POW2 * BUCKETS_PER_POW2) ? PERL_PAGESIZE : 0)
#else /* !TWO_POT_OPTIMIZE */
# define POW2_OPTIMIZE_ADJUST(nbytes)
# define POW2_OPTIMIZE_SURPLUS(bucket) 0
#endif /* !TWO_POT_OPTIMIZE */
#if defined(HAS_64K_LIMIT) && defined(PERL_CORE)
# define BARK_64K_LIMIT(what,nbytes,size) \
if (nbytes > 0xffff) { \
PerlIO_printf(PerlIO_stderr(), \
"%s too large: %lx\n", what, size); \
my_exit(1); \
}
#else /* !HAS_64K_LIMIT || !PERL_CORE */
# define BARK_64K_LIMIT(what,nbytes,size)
#endif /* !HAS_64K_LIMIT || !PERL_CORE */
#ifndef MIN_SBRK
# define MIN_SBRK 2048
#endif
#ifndef FIRST_SBRK
# define FIRST_SBRK (48*1024)
#endif
/* Minimal sbrk in percents of what is already alloced. */
#ifndef MIN_SBRK_FRAC
# define MIN_SBRK_FRAC 3
#endif
#ifndef SBRK_ALLOW_FAILURES
# define SBRK_ALLOW_FAILURES 3
#endif
#ifndef SBRK_FAILURE_PRICE
# define SBRK_FAILURE_PRICE 50
#endif
static void morecore (register int bucket);
# if defined(DEBUGGING)
static void botch (const char *diag, const char *s, const char *file, int line);
# endif
static void add_to_chain (void *p, MEM_SIZE size, MEM_SIZE chip);
static void* get_from_chain (MEM_SIZE size);
static void* get_from_bigger_buckets(int bucket, MEM_SIZE size);
static union overhead *getpages (MEM_SIZE needed, int *nblksp, int bucket);
static int getpages_adjacent(MEM_SIZE require);
#ifdef PERL_CORE
#ifdef I_MACH_CTHREADS
# undef MUTEX_LOCK
# define MUTEX_LOCK(m) STMT_START { if (*m) mutex_lock(*m); } STMT_END
# undef MUTEX_UNLOCK
# define MUTEX_UNLOCK(m) STMT_START { if (*m) mutex_unlock(*m); } STMT_END
#endif
#endif /* defined PERL_CORE */
#ifndef PTRSIZE
# define PTRSIZE sizeof(void*)
#endif
#ifndef BITS_IN_PTR
# define BITS_IN_PTR (8*PTRSIZE)
#endif
/*
* nextf[i] is the pointer to the next free block of size 2^i. The
* smallest allocatable block is 8 bytes. The overhead information
* precedes the data area returned to the user.
*/
#define NBUCKETS (BITS_IN_PTR*BUCKETS_PER_POW2 + 1)
static union overhead *nextf[NBUCKETS];
#if defined(PURIFY) && !defined(USE_PERL_SBRK)
# define USE_PERL_SBRK
#endif
#ifdef USE_PERL_SBRK
# define sbrk(a) Perl_sbrk(a)
Malloc_t Perl_sbrk (int size);
#else
# ifndef HAS_SBRK_PROTO /* <unistd.h> usually takes care of this */
extern Malloc_t sbrk(int);
# endif
#endif
#ifndef MIN_SBRK_FRAC1000 /* Backward compatibility */
# define MIN_SBRK_FRAC1000 (MIN_SBRK_FRAC * 10)
#endif
#ifndef START_EXTERN_C
# ifdef __cplusplus
# define START_EXTERN_C extern "C" {
# else