acalloc, acreate, adelete, afree, amallinfo, amalloc,
amallopt, amallocblksize, arealloc, nacreate - arena memory
#include <sys/types.h> #include <malloc.h> #include
void *(*grow_func)(size_t, void *) ); void *nacreate(
memalloc_attr_t *attr ); int adelete(
void *ap ); void *amalloc(
void *ap ); void afree(
void *ap ); void *arealloc(
void *ap ); void *acalloc(
void *ap ); size_t amallocblksize(
void *ap );
The following function definitions are provided only for
System V compatibility: int amallopt(
void *ap ); struct mallinfo amallinfo(
void *ap );
Standard C Library (libc.so, libc.a)
A pointer to a buffer used to hold the arena header information.
The size of the buffer in bytes (minimum 1K).
Attributes of the arena as the bitwise inclusive OR of any
combination of MEM_NOAUTOGROW and MEM_NONCONCURRENT. Currently
unused and must be NULL. For non-growing arenas,
NULL; for growing arenas, a function to be called when the
allocator requires more memory. Points to the memory
allocation policy and attributes to be used for allocations
from the new arena. A pointer to the arena. A number
of bytes of memory. A pointer to a block of memory.
The number of elements in an array. The size of each element
in an array. A command for the amallopt() function.
The amalloc family of routines provides a main memory
allocator based on the malloc(3) memory allocator. This
allocator has been extended so that an arbitrary memory
space ("arena") can be set up as an area from which to
Calls to the amalloc family of routines differ from calls
to the standard malloc(3) only in that an arena pointer
must be supplied. This arena pointer is returned by a call
to acreate() or nacreate().
For the acreate() and nacreate() functions, the flags
parameter specifies the attributes of a newly created
arena: MEM_NOAUTOGROW -- Causes the grow_func argument to
be ignored and inhibits any attempt to expand the arena
beyond the size len of the initial buffer. This parameter
is not allowed in nacreate(). MEM_NONCONCURRENT -- Turns
off all attempts to use locking and atomic updates for
this arena when allocating and freeing memory. This has an
affect only when the calling code is multithreaded. In
this case, allocations and frees using the arena may happen
faster, but the user must be extremely careful to
guarantee that no two threads reference this arena at the
same time in arena operations.
Function descriptions: Sets up an area defined as starting
at virtual address addr and extending for len bytes. Arenas
can be either growing or non-growing.
An arena that is non-growing is constrained to use
only up to len bytes of memory. The grow_func
parameter should be NULL in this case.
If the arena is "growable", len specifies the original
size (minimum of 1K bytes) and the grow_func
parameter specifies a function that will be called
when the allocator requires more memory. Note that
the original buffer addr will be used only for the
arena header; the first time more memory is
required, the "grow" function will be called.
The grow function will be called with two parameters:
the number of bytes required and a pointer to
the arena requiring the space. The number of bytes
requested will always be a multiple of M_BLKSZ (see
<malloc.h> header file). The function should return
the address of a suitably large block of memory.
This block does not need to be contiguous with the
original arena memory. This block could be obtained
from a number of sources, such as by mapping in
another file (by means of mmap(2)) or by calling
malloc(3) to enlarge the program's data space. If
the grow function decides that it cannot provide
any more space, it must return (void*)-1.
The ushdr function is currently unused and must be
NULL. Allocates an arena header and sets up a new
growable arena. The location for the arena is
determined automatically. The arena will use
nmmap() internally to obtain memory from the operating
system, passing in the saved attr parameter.
Note that use of the MEM_NOAUTOGROW flag is not
allowed in calls to nacreate(). The returned arena
may be used in all other arena malloc functions;
however, it is not specified whether memory freed
by afree() from this arena is ever released for
reuse outside the arena. Causes any resources
allocated for the arena (for example, mutexes) to
be freed. Nothing is done with the arena memory
itself. No additional calls to any arena functions
can be made after calling adelete(). Returns a
pointer to a block of at least size bytes suitably
aligned for any use. Destroys the contents of a
block previously allocated by amalloc(), arealloc(),
or acalloc() and makes this space available
for future allocation. The argument to afree() is a
pointer to the block previously allocated by amalloc(),
arealloc(), or acalloc().
Undefined results will occur if the space assigned
by any of the three arena allocator functions is
overrun or if some random number is handed to
afree(). It is always permitted to pass NULL to
afree(). Changes the size of the block pointed to
by ptr to size bytes and returns a pointer to the
(possibly moved) block. The contents will be
unchanged, up to the lesser of the new and old
sizes. In the special case of a null ptr, arealloc()
degenerates to amalloc(). A zero size causes
the passed block to be freed. Allocates space for
an array of num_elts elements of size elt_size. The
space is initialized to zeros. Returns the actual
size of the block pointed to by ptr. The returned
size may be greater than the original requested
size. Provides for control over the allocation
algorithm. The available values for cmd are defined
in the <malloc.h> header file.
The amallopt() function can be called repeatedly
but, for most commands, not after the first small
block is allocated. Provides instrumentation
describing space usage. It returns the mallinfo()
structure defined in the <malloc.h> header file.
The structure is zero until after the first space
has been allocated from the arena.
Each of the allocation routines returns a pointer to space
suitably aligned for storage of any type of object.
The acreate() function returns NULL and sets errno if
either len is less than 1K or the MEM_SHARED flag is
The amalloc(), arealloc(), and acalloc() functions return
a NULL pointer if there is not enough available memory.
When arealloc() returns NULL, the block pointed to by ptr
is left intact. If amallopt() is called after any allocation
(for most cmd arguments) or if cmd or value is
invalid, nonzero is returned. Otherwise, it returns zero.
Functions: malloc(3), nmmap(2), numa_intro(3),
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