XALLOC(9) XALLOC(9)
NAME
xalloc, xallocz, xspanalloc, xfree, xsummary - basic memory
management
SYNOPSIS
void* xalloc(ulong size)
void* xallocz(ulong size, int clr)
void* xspanalloc(ulong size, int align, ulong span)
void xfree(void *p)
void xsummary(void)
DESCRIPTION
These are primitives used by higher-level memory allocators
in the kernel, such as malloc(9). They are not intended for
use directly by most kernel routines. The main exceptions
are routines that permanently allocate large structures, or
need the special alignment properties guaranteed by
xspanalloc.
Xalloc returns a pointer to a range of size bytes of memory.
The memory will be zero filled and aligned on a 8 byte
(BY2V) address. If the memory is not available, xalloc
returns a null pointer.
Xmallocz will clear the memory after allocation if clr is
set to a value other than zero. Since it is used by xmalloc,
the same diagnostics apply.
Xspanalloc allocates memory given alignment and spanning
constraints. The block returned will contain size bytes,
aligned on a boundary that is 0 mod align, in such a way
that the memory in the block does not span an address that
is 0 mod span. Xspanalloc is intended for use allocating
hardware data structures (eg, page tables) or I/O buffers
that must satisfy specific alignment restrictions. If
xspanalloc cannot allocate memory to satisfy the given con-
straints, it will panic(9). The technique it uses can some-
times cause memory to be wasted. Consequently, xspanalloc
should be used sparingly.
Xfree frees the block of memory at p, which must be an
address previously returned by xalloc (not xspanalloc).
Xsummary dumps memory allocation statistics to the console.
The output includes the total free space, the number of free
holes, and a summary of active holes. Each line shows
Page 1 Plan 9 (printed 4/16/24)
XALLOC(9) XALLOC(9)
`address top size'.
SOURCE
/sys/src/9/port/xalloc.c
SEE ALSO
malloc(9)
Page 2 Plan 9 (printed 4/16/24)