XALLOC(10.2) XALLOC(10.2)
NAME
xalloc, xspanalloc, xfree - basic memory management
SYNOPSIS
void* xalloc(ulong size)
void* xspanalloc(ulong size, int align, ulong span)
void xfree(void *p)
DESCRIPTION
Xalloc and xfree are primitives used by higher-level memory
allocators in the kernel, such as malloc(10.2). 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 guaran-
teed 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.
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(10.2). The technique it uses can
sometimes 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).
Allocation status
Some memory allocation statistics are written to the console
in response to the debugging sequence `control-T control-T
x'. The output includes the total free space, the number of
free holes, and a summary of active holes. Each line shows
`address top size'.
SEE ALSO
malloc(10.2)
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