0b6f0c70db
this change adds some of the kernel manpages from 9legacy, fixed and updated to match the changes in 9front.
81 lines
2 KiB
Text
81 lines
2 KiB
Text
.TH XALLOC 9
|
|
.SH NAME
|
|
xalloc, xallocz, xspanalloc, xfree, xsummary \- basic memory management
|
|
.SH SYNOPSIS
|
|
.ta \w'\fLvoid* 'u
|
|
.B
|
|
void* xalloc(ulong size)
|
|
.PP
|
|
.B
|
|
void* xallocz(ulong size, int clr)
|
|
.PP
|
|
.B
|
|
void* xspanalloc(ulong size, int align, ulong span)
|
|
.PP
|
|
.B
|
|
void xfree(void *p)
|
|
.PP
|
|
.B
|
|
void xsummary(void)
|
|
.SH DESCRIPTION
|
|
These are primitives used by higher-level memory allocators in the kernel,
|
|
such as
|
|
.IR 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
|
|
.IR xspanalloc .
|
|
.PP
|
|
.I Xalloc
|
|
returns a pointer to a range of size bytes of memory. The memory will be zero filled and aligned on a 8 byte
|
|
.RB ( BY2V )
|
|
address. If the memory is not available,
|
|
.B xalloc
|
|
returns a null pointer.
|
|
.PP
|
|
.I Xmallocz
|
|
will clear the memory after allocation if
|
|
.I clr
|
|
is set to a value other than zero. Since it is used by
|
|
.IR xmalloc ,
|
|
the same diagnostics apply.
|
|
.PP
|
|
.I Xspanalloc
|
|
allocates memory given alignment and spanning constraints.
|
|
The block returned will contain
|
|
.I size
|
|
bytes, aligned on a boundary that is
|
|
.BI "0 mod" " align,"
|
|
in such a way that the memory in the block does not
|
|
span an address that is
|
|
.BI "0 mod" " span."
|
|
.I Xspanalloc
|
|
is intended for use
|
|
allocating hardware data structures (eg, page tables) or I/O buffers
|
|
that must satisfy specific alignment restrictions.
|
|
If
|
|
.I xspanalloc
|
|
cannot allocate memory to satisfy the given constraints, it will
|
|
.IR panic (9).
|
|
The technique it uses can sometimes cause memory to be wasted.
|
|
Consequently,
|
|
.I xspanalloc
|
|
should be used sparingly.
|
|
.PP
|
|
.I Xfree
|
|
frees the block of memory at
|
|
.IR p ,
|
|
which must be an address previously returned by
|
|
.I xalloc
|
|
(not
|
|
.IR xspanalloc ).
|
|
.PP
|
|
.I 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 `address top size'.
|
|
.SH SOURCE
|
|
.B /sys/src/9/port/xalloc.c
|
|
.SH SEE ALSO
|
|
.IR malloc (9)
|