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Annotation of src/sys/kern/bufq_priocscan.c, Revision 1.4

1.4     ! yamt        1: /*     $NetBSD: bufq_priocscan.c,v 1.3 2004/11/25 04:52:24 yamt Exp $  */
1.1       yamt        2:
                      3: /*-
                      4:  * Copyright (c)2004 YAMAMOTO Takashi,
                      5:  * All rights reserved.
                      6:  *
                      7:  * Redistribution and use in source and binary forms, with or without
                      8:  * modification, are permitted provided that the following conditions
                      9:  * are met:
                     10:  * 1. Redistributions of source code must retain the above copyright
                     11:  *    notice, this list of conditions and the following disclaimer.
                     12:  * 2. Redistributions in binary form must reproduce the above copyright
                     13:  *    notice, this list of conditions and the following disclaimer in the
                     14:  *    documentation and/or other materials provided with the distribution.
                     15:  *
                     16:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
                     17:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     18:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     19:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
                     20:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     21:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     22:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     23:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     24:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     25:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     26:  * SUCH DAMAGE.
                     27:  */
                     28:
                     29: #include <sys/cdefs.h>
1.4     ! yamt       30: __KERNEL_RCSID(0, "$NetBSD: bufq_priocscan.c,v 1.3 2004/11/25 04:52:24 yamt Exp $");
1.1       yamt       31:
                     32: #include <sys/param.h>
                     33: #include <sys/systm.h>
                     34: #include <sys/buf.h>
1.2       yamt       35: #include <sys/bufq.h>
1.1       yamt       36: #include <sys/malloc.h>
                     37:
                     38: /*
                     39:  * Cyclical scan (CSCAN)
                     40:  */
                     41: TAILQ_HEAD(bqhead, buf);
                     42: struct cscan_queue {
                     43:        struct bqhead cq_head[2];       /* actual lists of buffers */
                     44:        int cq_idx;                     /* current list index */
                     45:        int cq_lastcylinder;            /* b_cylinder of the last request */
                     46:        daddr_t cq_lastrawblkno;        /* b_rawblkno of the last request */
                     47: };
                     48:
                     49: static int __inline cscan_empty(const struct cscan_queue *);
                     50: static void cscan_put(struct cscan_queue *, struct buf *, int);
                     51: static struct buf *cscan_get(struct cscan_queue *, int);
                     52: static void cscan_init(struct cscan_queue *);
                     53:
                     54: static __inline int
                     55: cscan_empty(const struct cscan_queue *q)
                     56: {
                     57:
                     58:        return TAILQ_EMPTY(&q->cq_head[0]) && TAILQ_EMPTY(&q->cq_head[1]);
                     59: }
                     60:
                     61: static void
                     62: cscan_put(struct cscan_queue *q, struct buf *bp, int sortby)
                     63: {
                     64:        struct buf tmp;
                     65:        struct buf *it;
                     66:        struct bqhead *bqh;
                     67:        int idx;
                     68:
                     69:        tmp.b_cylinder = q->cq_lastcylinder;
                     70:        tmp.b_rawblkno = q->cq_lastrawblkno;
                     71:
                     72:        if (buf_inorder(bp, &tmp, sortby))
                     73:                idx = 1 - q->cq_idx;
                     74:        else
                     75:                idx = q->cq_idx;
                     76:
                     77:        bqh = &q->cq_head[idx];
                     78:
                     79:        TAILQ_FOREACH(it, bqh, b_actq)
                     80:                if (buf_inorder(bp, it, sortby))
                     81:                        break;
                     82:
                     83:        if (it != NULL)
                     84:                TAILQ_INSERT_BEFORE(it, bp, b_actq);
                     85:        else
                     86:                TAILQ_INSERT_TAIL(bqh, bp, b_actq);
                     87: }
                     88:
                     89: static struct buf *
                     90: cscan_get(struct cscan_queue *q, int remove)
                     91: {
                     92:        int idx = q->cq_idx;
                     93:        struct bqhead *bqh;
                     94:        struct buf *bp;
                     95:
                     96:        bqh = &q->cq_head[idx];
                     97:        bp = TAILQ_FIRST(bqh);
                     98:
                     99:        if (bp == NULL) {
                    100:                /* switch queue */
                    101:                idx = 1 - idx;
                    102:                bqh = &q->cq_head[idx];
                    103:                bp = TAILQ_FIRST(bqh);
                    104:        }
                    105:
                    106:        KDASSERT((bp != NULL && !cscan_empty(q)) ||
                    107:                 (bp == NULL && cscan_empty(q)));
                    108:
                    109:        if (bp != NULL && remove) {
                    110:                q->cq_idx = idx;
                    111:                TAILQ_REMOVE(bqh, bp, b_actq);
                    112:
                    113:                q->cq_lastcylinder = bp->b_cylinder;
                    114:                q->cq_lastrawblkno =
                    115:                    bp->b_rawblkno + (bp->b_bcount >> DEV_BSHIFT);
                    116:        }
                    117:
                    118:        return (bp);
                    119: }
                    120:
                    121: static void
                    122: cscan_init(struct cscan_queue *q)
                    123: {
                    124:
                    125:        TAILQ_INIT(&q->cq_head[0]);
                    126:        TAILQ_INIT(&q->cq_head[1]);
                    127: }
                    128:
                    129:
                    130: /*
                    131:  * Per-prioritiy CSCAN.
                    132:  *
                    133:  * XXX probably we should have a way to raise
                    134:  * priority of the on-queue requests.
                    135:  */
                    136: #define        PRIOCSCAN_NQUEUE        3
                    137:
                    138: struct priocscan_queue {
                    139:        struct cscan_queue q_queue;
                    140:        int q_burst;
                    141: };
                    142:
                    143: struct bufq_priocscan {
                    144:        struct priocscan_queue bq_queue[PRIOCSCAN_NQUEUE];
                    145:
                    146: #if 0
                    147:        /*
                    148:         * XXX using "global" head position can reduce positioning time
                    149:         * when switching between queues.
                    150:         * although it might affect against fairness.
                    151:         */
                    152:        daddr_t bq_lastrawblkno;
                    153:        int bq_lastcylinder;
                    154: #endif
                    155: };
                    156:
                    157: /*
                    158:  * how many requests to serve when having pending requests on other queues.
                    159:  *
                    160:  * XXX tune
                    161:  */
                    162: const int priocscan_burst[] = {
                    163:        64, 16, 4
                    164: };
                    165:
1.3       yamt      166: static void bufq_priocscan_init(struct bufq_state *);
1.1       yamt      167: static void bufq_priocscan_put(struct bufq_state *, struct buf *);
                    168: static struct buf *bufq_priocscan_get(struct bufq_state *, int);
1.3       yamt      169:
                    170: BUFQ_DEFINE(priocscan, BUFQ_PRIOCSCAN, bufq_priocscan_init);
                    171:
1.1       yamt      172: static __inline struct cscan_queue *bufq_priocscan_selectqueue(
                    173:     struct bufq_priocscan *, const struct buf *);
                    174:
                    175: static __inline struct cscan_queue *
                    176: bufq_priocscan_selectqueue(struct bufq_priocscan *q, const struct buf *bp)
                    177: {
                    178:        static const int priocscan_priomap[] = {
                    179:                [BPRIO_TIMENONCRITICAL] = 2,
                    180:                [BPRIO_TIMELIMITED] = 1,
                    181:                [BPRIO_TIMECRITICAL] = 0
                    182:        };
                    183:
                    184:        return &q->bq_queue[priocscan_priomap[BIO_GETPRIO(bp)]].q_queue;
                    185: }
                    186:
                    187: static void
                    188: bufq_priocscan_put(struct bufq_state *bufq, struct buf *bp)
                    189: {
                    190:        struct bufq_priocscan *q = bufq->bq_private;
                    191:        struct cscan_queue *cq;
                    192:        const int sortby = bufq->bq_flags & BUFQ_SORT_MASK;
                    193:
                    194:        cq = bufq_priocscan_selectqueue(q, bp);
                    195:        cscan_put(cq, bp, sortby);
                    196: }
                    197:
                    198: static struct buf *
                    199: bufq_priocscan_get(struct bufq_state *bufq, int remove)
                    200: {
                    201:        struct bufq_priocscan *q = bufq->bq_private;
                    202:        struct priocscan_queue *pq, *npq;
                    203:        struct priocscan_queue *first; /* first non-empty queue */
                    204:        const struct priocscan_queue *epq;
                    205:        const struct cscan_queue *cq;
                    206:        struct buf *bp;
                    207:        boolean_t single; /* true if there's only one non-empty queue */
                    208:
                    209:        pq = &q->bq_queue[0];
                    210:        epq = pq + PRIOCSCAN_NQUEUE;
                    211:        for (; pq < epq; pq++) {
                    212:                cq = &pq->q_queue;
                    213:                if (!cscan_empty(cq))
                    214:                        break;
                    215:        }
                    216:        if (pq == epq) {
                    217:                /* there's no requests */
                    218:                return NULL;
                    219:        }
                    220:
                    221:        first = pq;
                    222:        single = TRUE;
                    223:        for (npq = first + 1; npq < epq; npq++) {
                    224:                cq = &npq->q_queue;
                    225:                if (!cscan_empty(cq)) {
                    226:                        single = FALSE;
                    227:                        if (pq->q_burst > 0)
                    228:                                break;
                    229:                        pq = npq;
                    230:                }
                    231:        }
                    232:        if (single) {
                    233:                /*
                    234:                 * there's only a non-empty queue.  just serve it.
                    235:                 */
                    236:                pq = first;
                    237:        } else if (pq->q_burst > 0) {
                    238:                /*
                    239:                 * XXX account only by number of requests.  is it good enough?
                    240:                 */
1.4     ! yamt      241:                if (remove) {
        !           242:                        pq->q_burst--;
        !           243:                }
1.1       yamt      244:        } else {
                    245:                /*
                    246:                 * no queue was selected due to burst counts
                    247:                 */
                    248:                int i;
                    249: #ifdef DEBUG
                    250:                for (i = 0; i < PRIOCSCAN_NQUEUE; i++) {
                    251:                        pq = &q->bq_queue[i];
                    252:                        cq = &pq->q_queue;
                    253:                        if (!cscan_empty(cq) && pq->q_burst)
                    254:                                panic("%s: inconsist", __func__);
                    255:                }
                    256: #endif /* DEBUG */
                    257:
                    258:                /*
                    259:                 * reset burst counts
                    260:                 */
1.4     ! yamt      261:                if (remove) {
        !           262:                        for (i = 0; i < PRIOCSCAN_NQUEUE; i++) {
        !           263:                                pq = &q->bq_queue[i];
        !           264:                                pq->q_burst = priocscan_burst[i];
        !           265:                        }
1.1       yamt      266:                }
                    267:
                    268:                /*
                    269:                 * serve first non-empty queue.
                    270:                 */
                    271:                pq = first;
                    272:        }
                    273:
                    274:        KDASSERT(!cscan_empty(&pq->q_queue));
                    275:        bp = cscan_get(&pq->q_queue, remove);
                    276:        KDASSERT(bp != NULL);
                    277:        KDASSERT(&pq->q_queue == bufq_priocscan_selectqueue(q, bp));
                    278:
                    279:        return bp;
                    280: }
                    281:
1.3       yamt      282: static void
1.1       yamt      283: bufq_priocscan_init(struct bufq_state *bufq)
                    284: {
                    285:        struct bufq_priocscan *q;
                    286:        int i;
                    287:
                    288:        bufq->bq_get = bufq_priocscan_get;
                    289:        bufq->bq_put = bufq_priocscan_put;
                    290:        bufq->bq_private = malloc(sizeof(struct bufq_priocscan),
                    291:            M_DEVBUF, M_ZERO);
                    292:
                    293:        q = bufq->bq_private;
                    294:        for (i = 0; i < PRIOCSCAN_NQUEUE; i++) {
                    295:                struct cscan_queue *cq = &q->bq_queue[i].q_queue;
                    296:
                    297:                cscan_init(cq);
                    298:        }
                    299: }

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