bufq_readprio.c revision 1.8
1 /* $NetBSD: bufq_readprio.c,v 1.8 2007/04/04 02:30:43 wrstuden 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 1.8 2007/04/04 02:30:43 wrstuden 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/bufq_impl.h> 85 #include <sys/malloc.h> 86 87 /* 88 * Seek sort for disks. 89 * 90 * There are two queues. The first queue holds read requests; the second 91 * holds write requests. The read queue is first-come first-served; the 92 * write queue is sorted in ascendening block order. 93 * The read queue is processed first. After PRIO_READ_BURST consecutive 94 * read requests with non-empty write queue PRIO_WRITE_REQ requests from 95 * the write queue will be processed. 96 */ 97 98 #define PRIO_READ_BURST 48 99 #define PRIO_WRITE_REQ 16 100 101 struct bufq_prio { 102 TAILQ_HEAD(, buf) bq_read, bq_write; /* actual list of buffers */ 103 struct buf *bq_write_next; /* next request in bq_write */ 104 struct buf *bq_next; /* current request */ 105 int bq_read_burst; /* # of consecutive reads */ 106 }; 107 108 static void bufq_readprio_init(struct bufq_state *); 109 static void bufq_prio_put(struct bufq_state *, struct buf *); 110 static struct buf *bufq_prio_get(struct bufq_state *, int); 111 112 BUFQ_DEFINE(readprio, 30, bufq_readprio_init); 113 114 static void 115 bufq_prio_put(struct bufq_state *bufq, struct buf *bp) 116 { 117 struct bufq_prio *prio = bufq->bq_private; 118 struct buf *bq; 119 int sortby; 120 121 sortby = bufq->bq_flags & BUFQ_SORT_MASK; 122 123 /* 124 * If it's a read request append it to the list. 125 */ 126 if ((bp->b_flags & B_READ) == B_READ) { 127 TAILQ_INSERT_TAIL(&prio->bq_read, bp, b_actq); 128 return; 129 } 130 131 bq = TAILQ_FIRST(&prio->bq_write); 132 133 /* 134 * If the write list is empty, simply append it to the list. 135 */ 136 if (bq == NULL) { 137 TAILQ_INSERT_TAIL(&prio->bq_write, bp, b_actq); 138 prio->bq_write_next = bp; 139 return; 140 } 141 142 /* 143 * If we lie after the next request, insert after this request. 144 */ 145 if (buf_inorder(prio->bq_write_next, bp, sortby)) 146 bq = prio->bq_write_next; 147 148 /* 149 * Search for the first request at a larger block number. 150 * We go before this request if it exists. 151 */ 152 while (bq != NULL && buf_inorder(bq, bp, sortby)) 153 bq = TAILQ_NEXT(bq, b_actq); 154 155 if (bq != NULL) 156 TAILQ_INSERT_BEFORE(bq, bp, b_actq); 157 else 158 TAILQ_INSERT_TAIL(&prio->bq_write, bp, b_actq); 159 } 160 161 static struct buf * 162 bufq_prio_get(struct bufq_state *bufq, int remove) 163 { 164 struct bufq_prio *prio = bufq->bq_private; 165 struct buf *bp; 166 167 /* 168 * If no current request, get next from the lists. 169 */ 170 if (prio->bq_next == NULL) { 171 /* 172 * If at least one list is empty, select the other. 173 */ 174 if (TAILQ_FIRST(&prio->bq_read) == NULL) { 175 prio->bq_next = prio->bq_write_next; 176 prio->bq_read_burst = 0; 177 } else if (prio->bq_write_next == NULL) { 178 bp = prio->bq_next = TAILQ_FIRST(&prio->bq_read); 179 prio->bq_read_burst = 0; 180 KASSERT((bp == NULL) 181 || ((bp->b_flags & B_READ) == B_READ)); 182 } else { 183 /* 184 * Both list have requests. Select the read list up 185 * to PRIO_READ_BURST times, then select the write 186 * list PRIO_WRITE_REQ times. 187 */ 188 if (prio->bq_read_burst++ < PRIO_READ_BURST) 189 prio->bq_next = TAILQ_FIRST(&prio->bq_read); 190 else if (prio->bq_read_burst < 191 PRIO_READ_BURST + PRIO_WRITE_REQ) 192 prio->bq_next = prio->bq_write_next; 193 else { 194 prio->bq_next = TAILQ_FIRST(&prio->bq_read); 195 prio->bq_read_burst = 0; 196 } 197 } 198 } 199 200 bp = prio->bq_next; 201 202 if (bp != NULL && remove) { 203 if ((bp->b_flags & B_READ) == B_READ) 204 TAILQ_REMOVE(&prio->bq_read, bp, b_actq); 205 else { 206 /* 207 * Advance the write pointer before removing 208 * bp since it is actually prio->bq_write_next. 209 */ 210 prio->bq_write_next = 211 TAILQ_NEXT(prio->bq_write_next, b_actq); 212 TAILQ_REMOVE(&prio->bq_write, bp, b_actq); 213 if (prio->bq_write_next == NULL) 214 prio->bq_write_next = 215 TAILQ_FIRST(&prio->bq_write); 216 } 217 218 prio->bq_next = NULL; 219 } 220 221 return (bp); 222 } 223 224 static void 225 bufq_readprio_init(struct bufq_state *bufq) 226 { 227 struct bufq_prio *prio; 228 229 bufq->bq_get = bufq_prio_get; 230 bufq->bq_put = bufq_prio_put; 231 bufq->bq_private = malloc(sizeof(struct bufq_prio), M_DEVBUF, M_ZERO); 232 prio = (struct bufq_prio *)bufq->bq_private; 233 TAILQ_INIT(&prio->bq_read); 234 TAILQ_INIT(&prio->bq_write); 235 } 236 237
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