1 /* $OpenBSD: rf_cvscan.h,v 1.3 2002/12/16 07:01:03 tdeval Exp $ */
2 /* $NetBSD: rf_cvscan.h,v 1.3 1999/02/05 00:06:07 oster Exp $ */
3
4 /*
5 * Copyright (c) 1995 Carnegie-Mellon University.
6 * All rights reserved.
7 *
8 * Author: Mark Holland
9 *
10 * Permission to use, copy, modify and distribute this software and
11 * its documentation is hereby granted, provided that both the copyright
12 * notice and this permission notice appear in all copies of the
13 * software, derivative works or modified versions, and any portions
14 * thereof, and that both notices appear in supporting documentation.
15 *
16 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
17 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
18 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
19 *
20 * Carnegie Mellon requests users of this software to return to
21 *
22 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
23 * School of Computer Science
24 * Carnegie Mellon University
25 * Pittsburgh PA 15213-3890
26 *
27 * any improvements or extensions that they make and grant Carnegie the
28 * rights to redistribute these changes.
29 */
30
31 /*
32 * Disk scheduling by CVSCAN( N, r )
33 *
34 * Given a set of requests, partition them into one set on each
35 * side of the current arm position. The trick is to pick which
36 * side you are going to service next; once a side is picked you will
37 * service the closest request.
38 * Let there be n1 requests on one side and n2 requests on the other
39 * side. If one of n1 or n2 is zero, select the other side.
40 * If both n1 and n2 are nonzero, select a "range" for examination
41 * that is N' = min( n1, n2, N ). Average the distance from the
42 * current position to the nearest N' requests on each side giving
43 * d1 and d2.
44 * Suppose the last decision was to move toward set 2, then the
45 * current direction is toward set 2, and you will only switch to set
46 * 1 if d1+R < d2 where R is r*(total number of cylinders), r in [0,1].
47 *
48 * I extend this by applying only to the set of requests that all
49 * share the same, highest priority level.
50 */
51
52 #ifndef _RF__RF_CVSCAN_H_
53 #define _RF__RF_CVSCAN_H_
54
55 #include "rf_diskqueue.h"
56
57 typedef enum RF_CvscanArmDir_e {
58 rf_cvscan_LEFT,
59 rf_cvscan_RIGHT
60 } RF_CvscanArmDir_t;
61
62 typedef struct RF_CvscanHeader_s {
63 long range_for_avg; /* CVSCAN param N */
64 long change_penalty; /* CVSCAN param R */
65 RF_CvscanArmDir_t direction;
66 RF_SectorNum_t cur_block;
67 int nxt_priority;
68 RF_DiskQueueData_t *left;
69 int left_cnt;
70 RF_DiskQueueData_t *right;
71 int right_cnt;
72 RF_DiskQueueData_t *burner;
73 } RF_CvscanHeader_t;
74
75 int rf_CvscanConfigure(void);
76 void *rf_CvscanCreate(RF_SectorCount_t, RF_AllocListElem_t *,
77 RF_ShutdownList_t **);
78 void rf_CvscanEnqueue(void *, RF_DiskQueueData_t *, int);
79 RF_DiskQueueData_t *rf_CvscanDequeue(void *);
80 RF_DiskQueueData_t *rf_CvscanPeek(void *);
81 int rf_CvscanPromote(void *, RF_StripeNum_t, RF_ReconUnitNum_t);
82
83 #endif /* !_RF__RF_CVSCAN_H_ */