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 align‐
ment 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 mem‐
ory 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 can‐
not allocate memory to satisfy the given constraints, 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 previ‐
ously returned by xalloc (not xspanalloc).
Allocation status
Some memory allocation statistics are written to the console in
response to the debugging sequence 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)
XALLOC(10.2)
