bufq_readprio.c revision 1.12
1 /* $NetBSD: bufq_readprio.c,v 1.12 2009/01/16 01:48:09 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 * 21 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 23 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 24 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 25 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 26 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 27 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 28 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 29 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 30 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 31 * POSSIBILITY OF SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 1982, 1986, 1988, 1993 36 * The Regents of the University of California. All rights reserved. 37 * (c) UNIX System Laboratories, Inc. 38 * All or some portions of this file are derived from material licensed 39 * to the University of California by American Telephone and Telegraph 40 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 41 * the permission of UNIX System Laboratories, Inc. 42 * 43 * Redistribution and use in source and binary forms, with or without 44 * modification, are permitted provided that the following conditions 45 * are met: 46 * 1. Redistributions of source code must retain the above copyright 47 * notice, this list of conditions and the following disclaimer. 48 * 2. Redistributions in binary form must reproduce the above copyright 49 * notice, this list of conditions and the following disclaimer in the 50 * documentation and/or other materials provided with the distribution. 51 * 3. Neither the name of the University nor the names of its contributors 52 * may be used to endorse or promote products derived from this software 53 * without specific prior written permission. 54 * 55 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 56 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 57 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 58 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 59 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 60 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 61 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 62 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 63 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 64 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 65 * SUCH DAMAGE. 66 * 67 * @(#)ufs_disksubr.c 8.5 (Berkeley) 1/21/94 68 */ 69 70 #include <sys/cdefs.h> 71 __KERNEL_RCSID(0, "$NetBSD: bufq_readprio.c,v 1.12 2009/01/16 01:48:09 yamt Exp $"); 72 73 #include <sys/param.h> 74 #include <sys/systm.h> 75 #include <sys/buf.h> 76 #include <sys/bufq.h> 77 #include <sys/bufq_impl.h> 78 #include <sys/malloc.h> 79 80 /* 81 * Seek sort for disks. 82 * 83 * There are two queues. The first queue holds read requests; the second 84 * holds write requests. The read queue is first-come first-served; the 85 * write queue is sorted in ascendening block order. 86 * The read queue is processed first. After PRIO_READ_BURST consecutive 87 * read requests with non-empty write queue PRIO_WRITE_REQ requests from 88 * the write queue will be processed. 89 */ 90 91 #define PRIO_READ_BURST 48 92 #define PRIO_WRITE_REQ 16 93 94 struct bufq_prio { 95 TAILQ_HEAD(, buf) bq_read, bq_write; /* actual list of buffers */ 96 struct buf *bq_write_next; /* next request in bq_write */ 97 struct buf *bq_next; /* current request */ 98 int bq_read_burst; /* # of consecutive reads */ 99 }; 100 101 static void bufq_readprio_init(struct bufq_state *); 102 static void bufq_prio_put(struct bufq_state *, struct buf *); 103 static struct buf *bufq_prio_get(struct bufq_state *, int); 104 105 BUFQ_DEFINE(readprio, 30, bufq_readprio_init); 106 107 static void 108 bufq_prio_put(struct bufq_state *bufq, struct buf *bp) 109 { 110 struct bufq_prio *prio = bufq->bq_private; 111 struct buf *bq; 112 int sortby; 113 114 sortby = bufq->bq_flags & BUFQ_SORT_MASK; 115 116 /* 117 * If it's a read request append it to the list. 118 */ 119 if ((bp->b_flags & B_READ) == B_READ) { 120 TAILQ_INSERT_TAIL(&prio->bq_read, bp, b_actq); 121 return; 122 } 123 124 bq = TAILQ_FIRST(&prio->bq_write); 125 126 /* 127 * If the write list is empty, simply append it to the list. 128 */ 129 if (bq == NULL) { 130 TAILQ_INSERT_TAIL(&prio->bq_write, bp, b_actq); 131 prio->bq_write_next = bp; 132 return; 133 } 134 135 /* 136 * If we lie after the next request, insert after this request. 137 */ 138 if (buf_inorder(prio->bq_write_next, bp, sortby)) 139 bq = prio->bq_write_next; 140 141 /* 142 * Search for the first request at a larger block number. 143 * We go before this request if it exists. 144 */ 145 while (bq != NULL && buf_inorder(bq, bp, sortby)) 146 bq = TAILQ_NEXT(bq, b_actq); 147 148 if (bq != NULL) 149 TAILQ_INSERT_BEFORE(bq, bp, b_actq); 150 else 151 TAILQ_INSERT_TAIL(&prio->bq_write, bp, b_actq); 152 } 153 154 static struct buf * 155 bufq_prio_get(struct bufq_state *bufq, int remove) 156 { 157 struct bufq_prio *prio = bufq->bq_private; 158 struct buf *bp; 159 160 /* 161 * If no current request, get next from the lists. 162 */ 163 if (prio->bq_next == NULL) { 164 /* 165 * If at least one list is empty, select the other. 166 */ 167 if (TAILQ_FIRST(&prio->bq_read) == NULL) { 168 prio->bq_next = prio->bq_write_next; 169 prio->bq_read_burst = 0; 170 } else if (prio->bq_write_next == NULL) { 171 bp = prio->bq_next = TAILQ_FIRST(&prio->bq_read); 172 prio->bq_read_burst = 0; 173 KASSERT((bp == NULL) || 174 ((bp->b_flags & B_READ) == B_READ)); 175 } else { 176 /* 177 * Both list have requests. Select the read list up 178 * to PRIO_READ_BURST times, then select the write 179 * list PRIO_WRITE_REQ times. 180 */ 181 if (prio->bq_read_burst++ < PRIO_READ_BURST) 182 prio->bq_next = TAILQ_FIRST(&prio->bq_read); 183 else if (prio->bq_read_burst < 184 PRIO_READ_BURST + PRIO_WRITE_REQ) 185 prio->bq_next = prio->bq_write_next; 186 else { 187 prio->bq_next = TAILQ_FIRST(&prio->bq_read); 188 prio->bq_read_burst = 0; 189 } 190 } 191 } 192 193 bp = prio->bq_next; 194 195 if (bp != NULL && remove) { 196 if ((bp->b_flags & B_READ) == B_READ) 197 TAILQ_REMOVE(&prio->bq_read, bp, b_actq); 198 else { 199 /* 200 * Advance the write pointer before removing 201 * bp since it is actually prio->bq_write_next. 202 */ 203 prio->bq_write_next = 204 TAILQ_NEXT(prio->bq_write_next, b_actq); 205 TAILQ_REMOVE(&prio->bq_write, bp, b_actq); 206 if (prio->bq_write_next == NULL) 207 prio->bq_write_next = 208 TAILQ_FIRST(&prio->bq_write); 209 } 210 211 prio->bq_next = NULL; 212 } 213 214 return (bp); 215 } 216 217 static struct buf * 218 bufq_prio_cancel(struct bufq_state *bufq, struct buf *buf) 219 { 220 struct bufq_prio *prio = bufq->bq_private; 221 struct buf *bq; 222 223 /* search read queue */ 224 TAILQ_FOREACH(bq, &prio->bq_read, b_actq) { 225 if (bq == buf) { 226 TAILQ_REMOVE(&prio->bq_read, bq, b_actq); 227 /* force new section */ 228 prio->bq_next = NULL; 229 return buf; 230 } 231 } 232 233 /* not found in read queue, search write queue */ 234 TAILQ_FOREACH(bq, &prio->bq_write, b_actq) { 235 if (bq == buf) { 236 if (bq == prio->bq_write_next) { 237 /* 238 * Advance the write pointer before removing 239 * bp since it is actually prio->bq_write_next. 240 */ 241 prio->bq_write_next = 242 TAILQ_NEXT(prio->bq_write_next, b_actq); 243 TAILQ_REMOVE(&prio->bq_write, bq, b_actq); 244 if (prio->bq_write_next == NULL) 245 prio->bq_write_next = 246 TAILQ_FIRST(&prio->bq_write); 247 } else { 248 TAILQ_REMOVE(&prio->bq_write, bq, b_actq); 249 } 250 /* force new section */ 251 prio->bq_next = NULL; 252 return buf; 253 } 254 } 255 256 /* still not found */ 257 return NULL; 258 } 259 260 static void 261 bufq_readprio_init(struct bufq_state *bufq) 262 { 263 struct bufq_prio *prio; 264 265 bufq->bq_get = bufq_prio_get; 266 bufq->bq_put = bufq_prio_put; 267 bufq->bq_cancel = bufq_prio_cancel; 268 bufq->bq_private = malloc(sizeof(struct bufq_prio), M_DEVBUF, M_ZERO); 269 prio = (struct bufq_prio *)bufq->bq_private; 270 TAILQ_INIT(&prio->bq_read); 271 TAILQ_INIT(&prio->bq_write); 272 } 273 274
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