The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/bufq_disksort.c

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    1 /*      $NetBSD: bufq_disksort.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_disksort.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 actually two queues, sorted in ascendening order.  The first
   90  * queue holds those requests which are positioned after the current block;
   91  * the second holds requests which came in after their position was passed.
   92  * Thus we implement a one-way scan, retracting after reaching the end of
   93  * the drive to the first request on the second queue, at which time it
   94  * becomes the first queue.
   95  *
   96  * A one-way scan is natural because of the way UNIX read-ahead blocks are
   97  * allocated.
   98  */
   99 
  100 struct bufq_disksort {
  101         TAILQ_HEAD(, buf) bq_head;      /* actual list of buffers */
  102 };
  103 
  104 static void bufq_disksort_init(struct bufq_state *);
  105 static void bufq_disksort_put(struct bufq_state *, struct buf *);
  106 static struct buf *bufq_disksort_get(struct bufq_state *, int);
  107 
  108 BUFQ_DEFINE(disksort, BUFQ_DISKSORT, bufq_disksort_init);
  109 
  110 static void
  111 bufq_disksort_put(struct bufq_state *bufq, struct buf *bp)
  112 {
  113         struct bufq_disksort *disksort = bufq->bq_private;
  114         struct buf *bq, *nbq;
  115         int sortby;
  116 
  117         sortby = bufq->bq_flags & BUFQ_SORT_MASK;
  118 
  119         bq = TAILQ_FIRST(&disksort->bq_head);
  120 
  121         /*
  122          * If the queue is empty it's easy; we just go on the end.
  123          */
  124         if (bq == NULL) {
  125                 TAILQ_INSERT_TAIL(&disksort->bq_head, bp, b_actq);
  126                 return;
  127         }
  128 
  129         /*
  130          * If we lie before the currently active request, then we
  131          * must locate the second request list and add ourselves to it.
  132          */
  133         if (buf_inorder(bp, bq, sortby)) {
  134                 while ((nbq = TAILQ_NEXT(bq, b_actq)) != NULL) {
  135                         /*
  136                          * Check for an ``inversion'' in the normally ascending
  137                          * block numbers, indicating the start of the second
  138                          * request list.
  139                          */
  140                         if (buf_inorder(nbq, bq, sortby)) {
  141                                 /*
  142                                  * Search the second request list for the first
  143                                  * request at a larger block number.  We go
  144                                  * after that; if there is no such request, we
  145                                  * go at the end.
  146                                  */
  147                                 do {
  148                                         if (buf_inorder(bp, nbq, sortby))
  149                                                 goto insert;
  150                                         bq = nbq;
  151                                 } while ((nbq =
  152                                     TAILQ_NEXT(bq, b_actq)) != NULL);
  153                                 goto insert;            /* after last */
  154                         }
  155                         bq = nbq;
  156                 }
  157                 /*
  158                  * No inversions... we will go after the last, and
  159                  * be the first request in the second request list.
  160                  */
  161                 goto insert;
  162         }
  163         /*
  164          * Request is at/after the current request...
  165          * sort in the first request list.
  166          */
  167         while ((nbq = TAILQ_NEXT(bq, b_actq)) != NULL) {
  168                 /*
  169                  * We want to go after the current request if there is an
  170                  * inversion after it (i.e. it is the end of the first
  171                  * request list), or if the next request is a larger cylinder
  172                  * than our request.
  173                  */
  174                 if (buf_inorder(nbq, bq, sortby) ||
  175                     buf_inorder(bp, nbq, sortby))
  176                         goto insert;
  177                 bq = nbq;
  178         }
  179         /*
  180          * Neither a second list nor a larger request... we go at the end of
  181          * the first list, which is the same as the end of the whole schebang.
  182          */
  183 insert: TAILQ_INSERT_AFTER(&disksort->bq_head, bq, bp, b_actq);
  184 }
  185 
  186 static struct buf *
  187 bufq_disksort_get(struct bufq_state *bufq, int remove)
  188 {
  189         struct bufq_disksort *disksort = bufq->bq_private;
  190         struct buf *bp;
  191 
  192         bp = TAILQ_FIRST(&disksort->bq_head);
  193 
  194         if (bp != NULL && remove)
  195                 TAILQ_REMOVE(&disksort->bq_head, bp, b_actq);
  196 
  197         return (bp);
  198 }
  199 
  200 static void
  201 bufq_disksort_init(struct bufq_state *bufq)
  202 {
  203         struct bufq_disksort *disksort;
  204 
  205         bufq->bq_get = bufq_disksort_get;
  206         bufq->bq_put = bufq_disksort_put;
  207         MALLOC(bufq->bq_private, struct bufq_disksort *,
  208             sizeof(struct bufq_disksort), M_DEVBUF, M_ZERO);
  209         disksort = (struct bufq_disksort *)bufq->bq_private;
  210         TAILQ_INIT(&disksort->bq_head);
  211 }

Cache object: 685dc91ce737defedd5cb2b351aac578


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