1 /* $NetBSD: bufq_readprio.c,v 1.7 2005/12/11 12:24:29 christos 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 1.7 2005/12/11 12:24:29 christos 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 prio->bq_next = TAILQ_FIRST(&prio->bq_read);
179 prio->bq_read_burst = 0;
180 } else {
181 /*
182 * Both list have requests. Select the read list up
183 * to PRIO_READ_BURST times, then select the write
184 * list PRIO_WRITE_REQ times.
185 */
186 if (prio->bq_read_burst++ < PRIO_READ_BURST)
187 prio->bq_next = TAILQ_FIRST(&prio->bq_read);
188 else if (prio->bq_read_burst <
189 PRIO_READ_BURST + PRIO_WRITE_REQ)
190 prio->bq_next = prio->bq_write_next;
191 else {
192 prio->bq_next = TAILQ_FIRST(&prio->bq_read);
193 prio->bq_read_burst = 0;
194 }
195 }
196 }
197
198 bp = prio->bq_next;
199
200 if (bp != NULL && remove) {
201 if ((bp->b_flags & B_READ) == B_READ)
202 TAILQ_REMOVE(&prio->bq_read, bp, b_actq);
203 else {
204 /*
205 * Advance the write pointer before removing
206 * bp since it is actually prio->bq_write_next.
207 */
208 prio->bq_write_next =
209 TAILQ_NEXT(prio->bq_write_next, b_actq);
210 TAILQ_REMOVE(&prio->bq_write, bp, b_actq);
211 if (prio->bq_write_next == NULL)
212 prio->bq_write_next =
213 TAILQ_FIRST(&prio->bq_write);
214 }
215
216 prio->bq_next = NULL;
217 }
218
219 return (bp);
220 }
221
222 static void
223 bufq_readprio_init(struct bufq_state *bufq)
224 {
225 struct bufq_prio *prio;
226
227 bufq->bq_get = bufq_prio_get;
228 bufq->bq_put = bufq_prio_put;
229 bufq->bq_private = malloc(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
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