NetBSD/sys/kern/bufq_priocscan.c

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2009-01-19 17:54:28 +03:00
/* $NetBSD: bufq_priocscan.c,v 1.14 2009/01/19 14:54:28 yamt Exp $ */
/*-
* Copyright (c)2004,2005,2006,2008,2009 YAMAMOTO Takashi,
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: bufq_priocscan.c,v 1.14 2009/01/19 14:54:28 yamt Exp $");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/bufq.h>
#include <sys/bufq_impl.h>
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#include <sys/kmem.h>
/*
* Cyclical scan (CSCAN)
*/
TAILQ_HEAD(bqhead, buf);
struct cscan_queue {
struct bqhead cq_head[2]; /* actual lists of buffers */
int cq_idx; /* current list index */
int cq_lastcylinder; /* b_cylinder of the last request */
daddr_t cq_lastrawblkno; /* b_rawblkno of the last request */
};
static inline int cscan_empty(const struct cscan_queue *);
static void cscan_put(struct cscan_queue *, struct buf *, int);
static struct buf *cscan_get(struct cscan_queue *, int);
static void cscan_init(struct cscan_queue *);
static inline int
cscan_empty(const struct cscan_queue *q)
{
return TAILQ_EMPTY(&q->cq_head[0]) && TAILQ_EMPTY(&q->cq_head[1]);
}
static void
cscan_put(struct cscan_queue *q, struct buf *bp, int sortby)
{
struct buf tmp;
struct buf *it;
struct bqhead *bqh;
int idx;
tmp.b_cylinder = q->cq_lastcylinder;
tmp.b_rawblkno = q->cq_lastrawblkno;
if (buf_inorder(bp, &tmp, sortby))
idx = 1 - q->cq_idx;
else
idx = q->cq_idx;
bqh = &q->cq_head[idx];
TAILQ_FOREACH(it, bqh, b_actq)
if (buf_inorder(bp, it, sortby))
break;
if (it != NULL)
TAILQ_INSERT_BEFORE(it, bp, b_actq);
else
TAILQ_INSERT_TAIL(bqh, bp, b_actq);
}
static struct buf *
cscan_get(struct cscan_queue *q, int remove)
{
int idx = q->cq_idx;
struct bqhead *bqh;
struct buf *bp;
bqh = &q->cq_head[idx];
bp = TAILQ_FIRST(bqh);
if (bp == NULL) {
/* switch queue */
idx = 1 - idx;
bqh = &q->cq_head[idx];
bp = TAILQ_FIRST(bqh);
}
KDASSERT((bp != NULL && !cscan_empty(q)) ||
(bp == NULL && cscan_empty(q)));
if (bp != NULL && remove) {
q->cq_idx = idx;
TAILQ_REMOVE(bqh, bp, b_actq);
q->cq_lastcylinder = bp->b_cylinder;
q->cq_lastrawblkno =
bp->b_rawblkno + (bp->b_bcount >> DEV_BSHIFT);
}
return (bp);
}
static void
cscan_init(struct cscan_queue *q)
{
TAILQ_INIT(&q->cq_head[0]);
TAILQ_INIT(&q->cq_head[1]);
}
/*
* Per-prioritiy CSCAN.
*
* XXX probably we should have a way to raise
* priority of the on-queue requests.
*/
#define PRIOCSCAN_NQUEUE 3
struct priocscan_queue {
struct cscan_queue q_queue;
int q_burst;
};
struct bufq_priocscan {
struct priocscan_queue bq_queue[PRIOCSCAN_NQUEUE];
#if 0
/*
* XXX using "global" head position can reduce positioning time
* when switching between queues.
* although it might affect against fairness.
*/
daddr_t bq_lastrawblkno;
int bq_lastcylinder;
#endif
};
/*
* how many requests to serve when having pending requests on other queues.
*
* XXX tune
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* be careful: while making these values larger likely
* increases the total throughput, it can also increase latencies
* for some workloads.
*/
const int priocscan_burst[] = {
64, 16, 4
};
static void bufq_priocscan_init(struct bufq_state *);
static void bufq_priocscan_put(struct bufq_state *, struct buf *);
static struct buf *bufq_priocscan_get(struct bufq_state *, int);
BUFQ_DEFINE(priocscan, 40, bufq_priocscan_init);
static inline struct cscan_queue *bufq_priocscan_selectqueue(
struct bufq_priocscan *, const struct buf *);
static inline struct cscan_queue *
bufq_priocscan_selectqueue(struct bufq_priocscan *q, const struct buf *bp)
{
static const int priocscan_priomap[] = {
[BPRIO_TIMENONCRITICAL] = 2,
[BPRIO_TIMELIMITED] = 1,
[BPRIO_TIMECRITICAL] = 0
};
return &q->bq_queue[priocscan_priomap[BIO_GETPRIO(bp)]].q_queue;
}
static void
bufq_priocscan_put(struct bufq_state *bufq, struct buf *bp)
{
struct bufq_priocscan *q = bufq->bq_private;
struct cscan_queue *cq;
const int sortby = bufq->bq_flags & BUFQ_SORT_MASK;
cq = bufq_priocscan_selectqueue(q, bp);
cscan_put(cq, bp, sortby);
}
static struct buf *
bufq_priocscan_get(struct bufq_state *bufq, int remove)
{
struct bufq_priocscan *q = bufq->bq_private;
struct priocscan_queue *pq, *npq;
struct priocscan_queue *first; /* first non-empty queue */
const struct priocscan_queue *epq;
const struct cscan_queue *cq;
struct buf *bp;
bool single; /* true if there's only one non-empty queue */
pq = &q->bq_queue[0];
epq = pq + PRIOCSCAN_NQUEUE;
for (; pq < epq; pq++) {
cq = &pq->q_queue;
if (!cscan_empty(cq))
break;
}
if (pq == epq) {
/* there's no requests */
return NULL;
}
first = pq;
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single = true;
for (npq = first + 1; npq < epq; npq++) {
cq = &npq->q_queue;
if (!cscan_empty(cq)) {
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single = false;
if (pq->q_burst > 0)
break;
pq = npq;
}
}
if (single) {
/*
* there's only a non-empty queue. just serve it.
*/
pq = first;
} else if (pq->q_burst > 0) {
/*
* XXX account only by number of requests. is it good enough?
*/
if (remove) {
pq->q_burst--;
}
} else {
/*
* no queue was selected due to burst counts
*/
int i;
#ifdef DEBUG
for (i = 0; i < PRIOCSCAN_NQUEUE; i++) {
pq = &q->bq_queue[i];
cq = &pq->q_queue;
if (!cscan_empty(cq) && pq->q_burst)
panic("%s: inconsist", __func__);
}
#endif /* DEBUG */
/*
* reset burst counts
*/
if (remove) {
for (i = 0; i < PRIOCSCAN_NQUEUE; i++) {
pq = &q->bq_queue[i];
pq->q_burst = priocscan_burst[i];
}
}
/*
* serve first non-empty queue.
*/
pq = first;
}
KDASSERT(!cscan_empty(&pq->q_queue));
bp = cscan_get(&pq->q_queue, remove);
KDASSERT(bp != NULL);
KDASSERT(&pq->q_queue == bufq_priocscan_selectqueue(q, bp));
return bp;
}
static struct buf *
bufq_priocscan_cancel(struct bufq_state *bufq, struct buf *bp)
{
struct bufq_priocscan * const q = bufq->bq_private;
int i, j;
for (i = 0; i < PRIOCSCAN_NQUEUE; i++) {
struct cscan_queue * const cq = &q->bq_queue[i].q_queue;
for (j = 0; j < 2; j++) {
struct bqhead * const bqh = &cq->cq_head[j];
struct buf *bq;
TAILQ_FOREACH(bq, bqh, b_actq) {
if (bq == bp) {
TAILQ_REMOVE(bqh, bp, b_actq);
return bp;
}
}
}
}
return NULL;
}
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static void
bufq_priocscan_fini(struct bufq_state *bufq)
{
KASSERT(bufq->bq_private != NULL);
kmem_free(bufq->bq_private, sizeof(struct bufq_priocscan));
}
static void
bufq_priocscan_init(struct bufq_state *bufq)
{
struct bufq_priocscan *q;
int i;
bufq->bq_get = bufq_priocscan_get;
bufq->bq_put = bufq_priocscan_put;
bufq->bq_cancel = bufq_priocscan_cancel;
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bufq->bq_fini = bufq_priocscan_fini;
bufq->bq_private = kmem_zalloc(sizeof(struct bufq_priocscan), KM_SLEEP);
q = bufq->bq_private;
for (i = 0; i < PRIOCSCAN_NQUEUE; i++) {
struct cscan_queue *cq = &q->bq_queue[i].q_queue;
cscan_init(cq);
}
}