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
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