bufq_readprio.c revision 1.3
1 /* $NetBSD: bufq_readprio.c,v 1.3 2004/11/25 04:52:24 yamt Exp $ */ 2 /* NetBSD: subr_disk.c,v 1.61 2004/09/25 03:30:44 thorpej Exp */ 3 4 /*- 5 * Copyright (c) 1996, 1997, 1999, 2000 The NetBSD Foundation, Inc. 6 * All rights reserved. 7 * 8 * This code is derived from software contributed to The NetBSD Foundation 9 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, 10 * NASA Ames Research Center. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by the NetBSD 23 * Foundation, Inc. and its contributors. 24 * 4. Neither the name of The NetBSD Foundation nor the names of its 25 * contributors may be used to endorse or promote products derived 26 * from this software without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 29 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 30 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 31 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 32 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 33 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 34 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 35 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 36 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 37 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 38 * POSSIBILITY OF SUCH DAMAGE. 39 */ 40 41 /* 42 * Copyright (c) 1982, 1986, 1988, 1993 43 * The Regents of the University of California. All rights reserved. 44 * (c) UNIX System Laboratories, Inc. 45 * All or some portions of this file are derived from material licensed 46 * to the University of California by American Telephone and Telegraph 47 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 48 * the permission of UNIX System Laboratories, Inc. 49 * 50 * Redistribution and use in source and binary forms, with or without 51 * modification, are permitted provided that the following conditions 52 * are met: 53 * 1. Redistributions of source code must retain the above copyright 54 * notice, this list of conditions and the following disclaimer. 55 * 2. Redistributions in binary form must reproduce the above copyright 56 * notice, this list of conditions and the following disclaimer in the 57 * documentation and/or other materials provided with the distribution. 58 * 3. Neither the name of the University nor the names of its contributors 59 * may be used to endorse or promote products derived from this software 60 * without specific prior written permission. 61 * 62 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 63 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 64 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 65 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 66 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 67 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 68 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 69 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 70 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 71 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 72 * SUCH DAMAGE. 73 * 74 * @(#)ufs_disksubr.c 8.5 (Berkeley) 1/21/94 75 */ 76 77 #include <sys/cdefs.h> 78 __KERNEL_RCSID(0, "$NetBSD: bufq_readprio.c,v 1.3 2004/11/25 04:52:24 yamt Exp $"); 79 80 #include <sys/param.h> 81 #include <sys/systm.h> 82 #include <sys/buf.h> 83 #include <sys/bufq.h> 84 #include <sys/malloc.h> 85 86 /* 87 * Seek sort for disks. 88 * 89 * There are two queues. The first queue holds read requests; the second 90 * holds write requests. The read queue is first-come first-served; the 91 * write queue is sorted in ascendening block order. 92 * The read queue is processed first. After PRIO_READ_BURST consecutive 93 * read requests with non-empty write queue PRIO_WRITE_REQ requests from 94 * the write queue will be processed. 95 */ 96 97 #define PRIO_READ_BURST 48 98 #define PRIO_WRITE_REQ 16 99 100 struct bufq_prio { 101 TAILQ_HEAD(, buf) bq_read, bq_write; /* actual list of buffers */ 102 struct buf *bq_write_next; /* next request in bq_write */ 103 struct buf *bq_next; /* current request */ 104 int bq_read_burst; /* # of consecutive reads */ 105 }; 106 107 static void bufq_readprio_init(struct bufq_state *); 108 static void bufq_prio_put(struct bufq_state *, struct buf *); 109 static struct buf *bufq_prio_get(struct bufq_state *, int); 110 111 BUFQ_DEFINE(readprio, BUFQ_READ_PRIO, bufq_readprio_init); 112 113 static void 114 bufq_prio_put(struct bufq_state *bufq, struct buf *bp) 115 { 116 struct bufq_prio *prio = bufq->bq_private; 117 struct buf *bq; 118 int sortby; 119 120 sortby = bufq->bq_flags & BUFQ_SORT_MASK; 121 122 /* 123 * If it's a read request append it to the list. 124 */ 125 if ((bp->b_flags & B_READ) == B_READ) { 126 TAILQ_INSERT_TAIL(&prio->bq_read, bp, b_actq); 127 return; 128 } 129 130 bq = TAILQ_FIRST(&prio->bq_write); 131 132 /* 133 * If the write list is empty, simply append it to the list. 134 */ 135 if (bq == NULL) { 136 TAILQ_INSERT_TAIL(&prio->bq_write, bp, b_actq); 137 prio->bq_write_next = bp; 138 return; 139 } 140 141 /* 142 * If we lie after the next request, insert after this request. 143 */ 144 if (buf_inorder(prio->bq_write_next, bp, sortby)) 145 bq = prio->bq_write_next; 146 147 /* 148 * Search for the first request at a larger block number. 149 * We go before this request if it exists. 150 */ 151 while (bq != NULL && buf_inorder(bq, bp, sortby)) 152 bq = TAILQ_NEXT(bq, b_actq); 153 154 if (bq != NULL) 155 TAILQ_INSERT_BEFORE(bq, bp, b_actq); 156 else 157 TAILQ_INSERT_TAIL(&prio->bq_write, bp, b_actq); 158 } 159 160 static struct buf * 161 bufq_prio_get(struct bufq_state *bufq, int remove) 162 { 163 struct bufq_prio *prio = bufq->bq_private; 164 struct buf *bp; 165 166 /* 167 * If no current request, get next from the lists. 168 */ 169 if (prio->bq_next == NULL) { 170 /* 171 * If at least one list is empty, select the other. 172 */ 173 if (TAILQ_FIRST(&prio->bq_read) == NULL) { 174 prio->bq_next = prio->bq_write_next; 175 prio->bq_read_burst = 0; 176 } else if (prio->bq_write_next == NULL) { 177 prio->bq_next = TAILQ_FIRST(&prio->bq_read); 178 prio->bq_read_burst = 0; 179 } else { 180 /* 181 * Both list have requests. Select the read list up 182 * to PRIO_READ_BURST times, then select the write 183 * list PRIO_WRITE_REQ times. 184 */ 185 if (prio->bq_read_burst++ < PRIO_READ_BURST) 186 prio->bq_next = TAILQ_FIRST(&prio->bq_read); 187 else if (prio->bq_read_burst < 188 PRIO_READ_BURST + PRIO_WRITE_REQ) 189 prio->bq_next = prio->bq_write_next; 190 else { 191 prio->bq_next = TAILQ_FIRST(&prio->bq_read); 192 prio->bq_read_burst = 0; 193 } 194 } 195 } 196 197 bp = prio->bq_next; 198 199 if (bp != NULL && remove) { 200 if ((bp->b_flags & B_READ) == B_READ) 201 TAILQ_REMOVE(&prio->bq_read, bp, b_actq); 202 else { 203 /* 204 * Advance the write pointer before removing 205 * bp since it is actually prio->bq_write_next. 206 */ 207 prio->bq_write_next = 208 TAILQ_NEXT(prio->bq_write_next, b_actq); 209 TAILQ_REMOVE(&prio->bq_write, bp, b_actq); 210 if (prio->bq_write_next == NULL) 211 prio->bq_write_next = 212 TAILQ_FIRST(&prio->bq_write); 213 } 214 215 prio->bq_next = NULL; 216 } 217 218 return (bp); 219 } 220 221 static void 222 bufq_readprio_init(struct bufq_state *bufq) 223 { 224 struct bufq_prio *prio; 225 226 bufq->bq_get = bufq_prio_get; 227 bufq->bq_put = bufq_prio_put; 228 MALLOC(bufq->bq_private, struct bufq_prio *, 229 sizeof(struct bufq_prio), M_DEVBUF, M_ZERO); 230 prio = (struct bufq_prio *)bufq->bq_private; 231 TAILQ_INIT(&prio->bq_read); 232 TAILQ_INIT(&prio->bq_write); 233 } 234 235
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