NAME
mpipe_init,
mpipe_done,
mpipe_alloc_nowait,
mpipe_alloc_waitok,
mpipe_free —
malloc pipelines
SYNOPSIS
#include
<sys/mpipe.h>
void
mpipe_init(malloc_pipe_t
mpipe, malloc_type_t
type, int bytes,
int nnom,
int nmax,
int mpflags,
void (*construct)(void *, void
*), void
(*deconstruct)(void *, void *),
void *priv);
void
mpipe_done(malloc_pipe_t
mpipe);
void *
mpipe_alloc_nowait(malloc_pipe_t
mpipe);
void *
mpipe_alloc_waitok(malloc_pipe_t
mpipe);
void
mpipe_free(malloc_pipe_t
mpipe, void
*buf);
DESCRIPTION
A malloc pipeline is a linear pool of buffers of a single type. A malloc pipeline guarantees a number of outstanding allocations and provides both blocking and non-blocking behavior above the guaranteed allocation amounts. A malloc pipeline can have an upper limit, beyond which allocations sleep or fail respectively. Malloc pipelines are intended for situations where a minimum number of buffers are required to make progress.The
mpipe_init()
function initializes a malloc pipeline mpipe. The
pipeline allocates buffers of size bytes from the
malloc zone type. The pipeline is prefilled with
nnom buffers and has a limit of
nmax buffers. The construct
argument is a callback, invoked when a buffer is allocated from the system.
The deconstruct argument is a callback, invoked when
the malloc pipeline is destroyed or a buffer is freed to the system. Both
construct and deconstruct are
invoked with the buffer address as their first parameter and with
priv as their second parameter. The
flags argument controls allocation parameters:
MPF_NOZERO- Do not zero allocated buffers.
MPF_CACHEDATA- By default, MPIPE buffers are zeroed on free; this flag disables that behavior.
MPF_INT- Allocations may use the interrupt memory reserve.
This function may block.
The
mpipe_done()
function destroys a malloc pipeline. The pipeline's destructor is invoked on
each buffer and then they are returned to the system. It is an error to
invoke this function on a pipeline with outstanding allocations. This
function may block.
The
mpipe_alloc_nowait()
function allocates a buffer from the malloc pipeline. It will first allocate
from the pipeline itself; if that is exhausted, it will fall back on
kmalloc(9), up to the pipeline maximum. This function may not
block.
The
mpipe_alloc_waitok()
function allocates a buffer from the malloc pipeline. It will first allocate
from the pipeline; if that is exhausted, it will fall back on
kmalloc(9), up to the pipeline maximum. It will sleep if it reaches
the maximum, potentially releasing any tokens.
The
mpipe_free()
function frees a buffer to the malloc pipeline. If the pipeline is full, it
will free directly to the kernel allocator, calling the destructor as it
does. This function may block.
FILES
The MPIPE implementation is in /sys/kern/kern_mpipe.c.
SEE ALSO
HISTORY
MPIPE first appeared in DragonFly 1.0.