Annotation of sys/dev/raidframe/rf_cvscan.h, Revision 1.1.1.1
1.1 nbrk 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_ */
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