BUFQ(9) | Kernel Developer's Manual | BUFQ(9) |
bufq
, bufq_init
,
bufq_register
,
bufq_unregister
, bufq_state
,
bufq_alloc
, bufq_drain
,
bufq_free
,
bufq_getstrategyname
,
bufq_move
, bufq_put
,
bufq_get
, bufq_peek
,
bufq_cancel
—
#include <sys/bufq.h>
void
bufq_init
(void);
int
bufq_register
(struct
bufq_strat *);
int
bufq_unregister
(struct
bufq_strat *);
int
bufq_alloc
(struct
bufq_state **bufq, const
char *strategy, int
flags);
void
bufq_drain
(struct
bufq_state *bufq);
void
bufq_free
(struct
bufq_state *bufq);
const char *
bufq_getstrategyname
(struct
bufq_state *bufq);
void
bufq_move
(struct
bufq_state *dst, struct
bufq_state *src);
void
bufq_put
(struct
bufq_state *bufq, struct
buf *bp);
struct buf *
bufq_get
(struct
bufq_state *bufq);
struct buf *
bufq_peek
(struct
bufq_state *bufq);
struct buf *
bufq_cancel
(struct
bufq_state *bufq, struct
buf *bp);
bufq
subsystem is a set of operations for the
management of device buffer queues. Various strategies for ordering of entries
in the buffer queues can be provided by loadable kernel modules (see
module(9)). By default, the
BUFQ_FCFS
and BUFQ_DISKSORT
strategies are included in the kernel; see
options(4) for more details.
The primary data type for using the operations is the bufq_state structure, which is opaque for users. Each buffer queue strategy module is defined by the bufq_strat structure, which is also opaque for users.
bufq_init
(void)bufq
subsystem. This routine must
be called before any other bufq
routines.bufq_register
(bs)bufq_unregister
(bs)bufq_alloc
() below).bufq_alloc
(bufq,
strategy, flags)The argument strategy specifies a buffer queue strategy to be used for this buffer queue. The following special values can be used:
BUFQ_STRAT_ANY
bufq_alloc
() select a strategy.BUFQ_DISK_DEFAULT_STRAT
bufq_alloc
() select a strategy, assuming
it will be used for a normal disk device.Valid bits for the flags are:
BUFQ_SORT_RAWBLOCK
BUFQ_SORT_CYLINDER
BUFQ_EXACT
ENOENT
. If this flag is not specified,
bufq_alloc
() will silently use one of
available strategies.If a specific strategy is specified but not currently
available, the bufq
subsystem will attempt to
auto-load the corresponding kernel module using
module_autoload(9).
bufq_drain
(bufq)bufq_free
(bufq)bufq_getstrategyname
(bufq)bufq_move
(dst,
src)bufq_put
(bufq,
bp)bufq_get
(bufq)NULL
if the queue is empty.bufq_peek
(bufq)bufq_get
(),
bufq_put
(), or
bufq_drain
() is called. Returns
NULL
if the queue is empty.bufq_cancel
(bufq,
bp)NULL
if the element can not be found on
the queue or bp if it has been found and removed.
This operation can be computationally expensive if there are a lot of
buffers queued.bufq
subsystem appeared in NetBSD
2.0.
bufq
subsystem was written by
Jürgen Hannken-Illjes
⟨hannken@NetBSD.org⟩.
November 17, 2016 | NetBSD 9.0 |