1 /* $NetBSD: bufq_readprio.c,v 1.11 2008/04/30 12:09:02 reinoud 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 1.11 2008/04/30 12:09:02 reinoud 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 bq = TAILQ_FIRST(&prio->bq_read);
225 while (bq) {
226 if (bq == buf) {
227 TAILQ_REMOVE(&prio->bq_read, bq, b_actq);
228 /* force new section */
229 prio->bq_next = NULL;
230 return buf;
231 }
232 bq = TAILQ_NEXT(bq, b_actq);
233 }
234
235 /* not found in read queue, search write queue */
236 bq = TAILQ_FIRST(&prio->bq_write);
237 while (bq) {
238 if (bq == buf) {
239 if (bq == prio->bq_write_next) {
240 /*
241 * Advance the write pointer before removing
242 * bp since it is actually prio->bq_write_next.
243 */
244 prio->bq_write_next =
245 TAILQ_NEXT(prio->bq_write_next, b_actq);
246 TAILQ_REMOVE(&prio->bq_write, bq, b_actq);
247 if (prio->bq_write_next == NULL)
248 prio->bq_write_next =
249 TAILQ_FIRST(&prio->bq_write);
250 } else {
251 TAILQ_REMOVE(&prio->bq_write, bq, b_actq);
252 }
253 /* force new section */
254 prio->bq_next = NULL;
255 return buf;
256 }
257 bq = TAILQ_NEXT(bq, b_actq);
258 }
259
260 /* still not found */
261 return NULL;
262 }
263
264 static void
265 bufq_readprio_init(struct bufq_state *bufq)
266 {
267 struct bufq_prio *prio;
268
269 bufq->bq_get = bufq_prio_get;
270 bufq->bq_put = bufq_prio_put;
271 bufq->bq_cancel = bufq_prio_cancel;
272 bufq->bq_private = malloc(sizeof(struct bufq_prio), M_DEVBUF, M_ZERO);
273 prio = (struct bufq_prio *)bufq->bq_private;
274 TAILQ_INIT(&prio->bq_read);
275 TAILQ_INIT(&prio->bq_write);
276 }
277
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