Alien-Judy
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independent_comallac differs from independent_calloc in that each
element may have a different size, and also that it does not
automatically clear elements.
independent_comalloc can be used to speed up allocation in cases
where several structs or objects must always be allocated at the
same time. For example:
struct Head { ... }
struct Foot { ... }
void send_message(char* msg) {
int msglen = strlen(msg);
size_t sizes[3] = { sizeof(struct Head), msglen, sizeof(struct Foot) };
void* chunks[3];
if (independent_comalloc(3, sizes, chunks) == 0)
die();
struct Head* head = (struct Head*)(chunks[0]);
char* body = (char*)(chunks[1]);
struct Foot* foot = (struct Foot*)(chunks[2]);
// ...
}
In general though, independent_comalloc is worth using only for
larger values of n_elements. For small values, you probably won't
detect enough difference from series of malloc calls to bother.
Overuse of independent_comalloc can increase overall memory usage,
since it cannot reuse existing noncontiguous small chunks that
might be available for some of the elements.
*/
Void_t** public_iCOMALLOc(size_t, size_t*, Void_t**);
/*
pvalloc(size_t n);
Equivalent to valloc(minimum-page-that-holds(n)), that is,
round up n to nearest pagesize.
*/
Void_t* public_pVALLOc(size_t);
/*
cfree(Void_t* p);
Equivalent to free(p).
cfree is needed/defined on some systems that pair it with calloc,
for odd historical reasons (such as: cfree is used in example
code in the first edition of K&R).
*/
void public_cFREe(Void_t*);
/*
malloc_trim(size_t pad);
If possible, gives memory back to the system (via negative
arguments to sbrk) if there is unused memory at the `high' end of
the malloc pool. You can call this after freeing large blocks of
memory to potentially reduce the system-level memory requirements
of a program. However, it cannot guarantee to reduce memory. Under
some allocation patterns, some large free blocks of memory will be
locked between two used chunks, so they cannot be given back to
the system.
The `pad' argument to malloc_trim represents the amount of free
trailing space to leave untrimmed. If this argument is zero,
only the minimum amount of memory to maintain internal data
structures will be left (one page or less). Non-zero arguments
can be supplied to maintain enough trailing space to service
future expected allocations without having to re-obtain memory
from the system.
Malloc_trim returns 1 if it actually released any memory, else 0.
On systems that do not support "negative sbrks", it will always
rreturn 0.
*/
int public_mTRIm(size_t);
/*
malloc_usable_size(Void_t* p);
Returns the number of bytes you can actually use in
an allocated chunk, which may be more than you requested (although
often not) due to alignment and minimum size constraints.
You can use this many bytes without worrying about
overwriting other allocated objects. This is not a particularly great
programming practice. malloc_usable_size can be more useful in
debugging and assertions, for example:
p = malloc(n);
assert(malloc_usable_size(p) >= 256);
*/
size_t public_mUSABLe(Void_t*);
/*
malloc_stats();
Prints on stderr the amount of space obtained from the system (both
via sbrk and mmap), the maximum amount (which may be more than
current if malloc_trim and/or munmap got called), and the current
number of bytes allocated via malloc (or realloc, etc) but not yet
freed. Note that this is the number of bytes allocated, not the
number requested. It will be larger than the number requested
because of alignment and bookkeeping overhead. Because it includes
alignment wastage as being in use, this figure may be greater than
zero even when no user-level chunks are allocated.
The reported current and maximum system memory can be inaccurate if
a program makes other calls to system memory allocation functions
(normally sbrk) outside of malloc.
malloc_stats prints only the most commonly interesting statistics.
More information can be obtained by calling mallinfo.
*/
void public_mSTATs();
/* mallopt tuning options */
/*
M_MXFAST is the maximum request size used for "fastbins", special bins
that hold returned chunks without consolidating their spaces. This
src/judy-1.0.5/test/malloc-pre2.8a.c view on Meta::CPAN
*/
#define M_TRIM_THRESHOLD -1
#ifndef DEFAULT_TRIM_THRESHOLD
#define DEFAULT_TRIM_THRESHOLD (-1U)
/* #define DEFAULT_TRIM_THRESHOLD (256 * 1024) */
#endif
/*
M_TOP_PAD is the amount of extra `padding' space to allocate or
retain whenever sbrk is called. It is used in two ways internally:
* When sbrk is called to extend the top of the arena to satisfy
a new malloc request, this much padding is added to the sbrk
request.
* When malloc_trim is called automatically from free(),
it is used as the `pad' argument.
In both cases, the actual amount of padding is rounded
so that the end of the arena is always a system page boundary.
The main reason for using padding is to avoid calling sbrk so
often. Having even a small pad greatly reduces the likelihood
that nearly every malloc request during program start-up (or
after trimming) will invoke sbrk, which needlessly wastes
time.
Automatic rounding-up to page-size units is normally sufficient
to avoid measurable overhead, so the default is 0. However, in
systems where sbrk is relatively slow, it can pay to increase
this value, at the expense of carrying around more memory than
the program needs.
*/
#define M_TOP_PAD -2
#ifndef DEFAULT_TOP_PAD
#define DEFAULT_TOP_PAD (0)
#endif
/*
M_MMAP_THRESHOLD is the request size threshold for using mmap()
to service a request. Requests of at least this size that cannot
be allocated using already-existing space will be serviced via mmap.
(If enough normal freed space already exists it is used instead.)
Using mmap segregates relatively large chunks of memory so that
they can be individually obtained and released from the host
system. A request serviced through mmap is never reused by any
other request (at least not directly; the system may just so
happen to remap successive requests to the same locations).
Segregating space in this way has the benefits that:
1. Mmapped space can ALWAYS be individually released back
to the system, which helps keep the system level memory
demands of a long-lived program low.
2. Mapped memory can never become `locked' between
other chunks, as can happen with normally allocated chunks, which
means that even trimming via malloc_trim would not release them.
3. On some systems with "holes" in address spaces, mmap can obtain
memory that sbrk cannot.
However, it has the disadvantages that:
1. The space cannot be reclaimed, consolidated, and then
used to service later requests, as happens with normal chunks.
2. It can lead to more wastage because of mmap page alignment
requirements
3. It causes malloc performance to be more dependent on host
system memory management support routines which may vary in
implementation quality and may impose arbitrary
limitations. Generally, servicing a request via normal
malloc steps is faster than going through a system's mmap.
The advantages of mmap nearly always outweigh disadvantages for
"large" chunks, but the value of "large" varies across systems. The
default is an empirically derived value that works well in most
systems.
*/
#define M_MMAP_THRESHOLD -3
#ifndef DEFAULT_MMAP_THRESHOLD
#define DEFAULT_MMAP_THRESHOLD (-1U)
/*#define DEFAULT_MMAP_THRESHOLD (128 * 1024) */
#endif
/*
M_MMAP_MAX is the maximum number of requests to simultaneously
service using mmap. This parameter exists because
. Some systems have a limited number of internal tables for
use by mmap, and using more than a few of them may degrade
performance.
The default is set to a value that serves only as a safeguard.
Setting to 0 disables use of mmap for servicing large requests. If
HAVE_MMAP is not set, the default value is 0, and attempts to set it
to non-zero values in mallopt will fail.
*/
#define M_MMAP_MAX -4
#ifndef DEFAULT_MMAP_MAX
#if HAVE_MMAP
#define DEFAULT_MMAP_MAX (65536)
#else
#define DEFAULT_MMAP_MAX (0)
#endif
#endif
#ifdef __cplusplus
}; /* end of extern "C" */
#endif
/*
========================================================================
To make a fully customizable malloc.h header file, cut everything
src/judy-1.0.5/test/malloc-pre2.8a.c view on Meta::CPAN
else (i.e. If MORECORE_CONTIGUOUS is true):
* Consecutive calls to MORECORE with positive arguments
return increasing addresses, indicating that space has been
contiguously extended.
* MORECORE need not allocate in multiples of pagesize.
Calls to MORECORE need not have args of multiples of pagesize.
* MORECORE need not page-align.
In either case:
* MORECORE may allocate more memory than requested. (Or even less,
but this will generally result in a malloc failure.)
* MORECORE must not allocate memory when given argument zero, but
instead return one past the end address of memory from previous
nonzero call. This malloc does NOT call MORECORE(0)
until at least one call with positive arguments is made, so
the initial value returned is not important.
* Even though consecutive calls to MORECORE need not return contiguous
addresses, it must be OK for malloc'ed chunks to span multiple
regions in those cases where they do happen to be contiguous.
* MORECORE need not handle negative arguments -- it may instead
just return MORECORE_FAILURE when given negative arguments.
Negative arguments are always multiples of pagesize. MORECORE
must not misinterpret negative args as large positive unsigned
args. You can suppress all such calls from even occurring by defining
MORECORE_CANNOT_TRIM,
There is some variation across systems about the type of the
argument to sbrk/MORECORE. If size_t is unsigned, then it cannot
actually be size_t, because sbrk supports negative args, so it is
normally the signed type of the same width as size_t (sometimes
declared as "intptr_t", and sometimes "ptrdiff_t"). It doesn't much
matter though. Internally, we use "long" as arguments, which should
work across all reasonable possibilities.
Additionally, if MORECORE ever returns failure for a positive
request, and HAVE_MMAP is true, then mmap is used as a noncontiguous
system allocator. This is a useful backup strategy for systems with
holes in address spaces -- in this case sbrk cannot contiguously
expand the heap, but mmap may be able to map noncontiguous space.
If you'd like mmap to ALWAYS be used, you can define MORECORE to be
a function that always returns MORECORE_FAILURE.
Malloc only has limited ability to detect failures of MORECORE
to supply contiguous space when it says it can. In particular,
multithreaded programs that do not use locks may result in
rece conditions across calls to MORECORE that result in gaps
that cannot be detected as such, and subsequent corruption.
If you are using this malloc with something other than sbrk (or its
emulation) to supply memory regions, you probably want to set
MORECORE_CONTIGUOUS as false. As an example, here is a custom
allocator kindly contributed for pre-OSX macOS. It uses virtually
but not necessarily physically contiguous non-paged memory (locked
in, present and won't get swapped out). You can use it by
uncommenting this section, adding some #includes, and setting up the
appropriate defines above:
#define MORECORE osMoreCore
#define MORECORE_CONTIGUOUS 0
There is also a shutdown routine that should somehow be called for
cleanup upon program exit.
#define MAX_POOL_ENTRIES 100
#define MINIMUM_MORECORE_SIZE (64 * 1024)
static int next_os_pool;
void *our_os_pools[MAX_POOL_ENTRIES];
void *osMoreCore(int size)
{
void *ptr = 0;
static void *sbrk_top = 0;
if (size > 0)
{
if (size < MINIMUM_MORECORE_SIZE)
size = MINIMUM_MORECORE_SIZE;
if (CurrentExecutionLevel() == kTaskLevel)
ptr = PoolAllocateResident(size + RM_PAGE_SIZE, 0);
if (ptr == 0)
{
return (void *) MORECORE_FAILURE;
}
// save ptrs so they can be freed during cleanup
our_os_pools[next_os_pool] = ptr;
next_os_pool++;
ptr = (void *) ((((CHUNK_SIZE_T) ptr) + RM_PAGE_MASK) & ~RM_PAGE_MASK);
sbrk_top = (char *) ptr + size;
return ptr;
}
else if (size < 0)
{
// we don't currently support shrink behavior
return (void *) MORECORE_FAILURE;
}
else
{
return sbrk_top;
}
}
// cleanup any allocated memory pools
// called as last thing before shutting down driver
void osCleanupMem(void)
{
void **ptr;
for (ptr = our_os_pools; ptr < &our_os_pools[MAX_POOL_ENTRIES]; ptr++)
if (*ptr)
{
PoolDeallocate(*ptr);
*ptr = 0;
}
}
*/
/*
--------------------------------------------------------------
Emulation of sbrk for win32.
Donated by J. Walter <Walter@GeNeSys-e.de>.
For additional information about this code, and malloc on Win32, see
http://www.genesys-e.de/jwalter/
*/
#ifdef WIN32
#ifdef _DEBUG
/* #define TRACE */
#endif
/* Support for USE_MALLOC_LOCK */
#ifdef USE_MALLOC_LOCK
/* Wait for spin lock */
static int slwait (int *sl) {
while (InterlockedCompareExchange ((void **) sl, (void *) 1, (void *) 0) != 0)
Sleep (0);
return 0;
}
/* Release spin lock */
static int slrelease (int *sl) {
InterlockedExchange (sl, 0);
return 0;
}
#ifdef NEEDED
/* Spin lock for emulation code */
static int g_sl;
#endif
#endif /* USE_MALLOC_LOCK */
/* getpagesize for windows */
static long getpagesize (void) {
static long g_pagesize = 0;
if (! g_pagesize) {
SYSTEM_INFO system_info;
GetSystemInfo (&system_info);
g_pagesize = system_info.dwPageSize;
}
return g_pagesize;
}
static long getregionsize (void) {
static long g_regionsize = 0;
if (! g_regionsize) {
SYSTEM_INFO system_info;
GetSystemInfo (&system_info);
g_regionsize = system_info.dwAllocationGranularity;
}
return g_regionsize;
}
/* A region list entry */
typedef struct _region_list_entry {
void *top_allocated;
void *top_committed;
void *top_reserved;
long reserve_size;
struct _region_list_entry *previous;
} region_list_entry;
/* Allocate and link a region entry in the region list */
static int region_list_append (region_list_entry **last, void *base_reserved, long reserve_size) {
region_list_entry *next = HeapAlloc (GetProcessHeap (), 0, sizeof (region_list_entry));
if (! next)
return FALSE;
next->top_allocated = (char *) base_reserved;
next->top_committed = (char *) base_reserved;
next->top_reserved = (char *) base_reserved + reserve_size;
next->reserve_size = reserve_size;
next->previous = *last;
*last = next;
return TRUE;
}
/* Free and unlink the last region entry from the region list */
static int region_list_remove (region_list_entry **last) {
region_list_entry *previous = (*last)->previous;
if (! HeapFree (GetProcessHeap (), sizeof (region_list_entry), *last))
return FALSE;
*last = previous;
return TRUE;
}
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