1 | /* $NetBSD: rf_cvscan.h,v 1.6 2005/12/11 12:23:37 christos Exp $ */ |
2 | /* |
3 | * Copyright (c) 1995 Carnegie-Mellon University. |
4 | * All rights reserved. |
5 | * |
6 | * Author: Mark Holland |
7 | * |
8 | * Permission to use, copy, modify and distribute this software and |
9 | * its documentation is hereby granted, provided that both the copyright |
10 | * notice and this permission notice appear in all copies of the |
11 | * software, derivative works or modified versions, and any portions |
12 | * thereof, and that both notices appear in supporting documentation. |
13 | * |
14 | * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" |
15 | * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND |
16 | * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. |
17 | * |
18 | * Carnegie Mellon requests users of this software to return to |
19 | * |
20 | * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU |
21 | * School of Computer Science |
22 | * Carnegie Mellon University |
23 | * Pittsburgh PA 15213-3890 |
24 | * |
25 | * any improvements or extensions that they make and grant Carnegie the |
26 | * rights to redistribute these changes. |
27 | */ |
28 | |
29 | /* |
30 | ** Disk scheduling by CVSCAN( N, r ) |
31 | ** |
32 | ** Given a set of requests, partition them into one set on each |
33 | ** side of the current arm position. The trick is to pick which |
34 | ** side you are going to service next; once a side is picked you will |
35 | ** service the closest request. |
36 | ** Let there be n1 requests on one side and n2 requests on the other |
37 | ** side. If one of n1 or n2 is zero, select the other side. |
38 | ** If both n1 and n2 are nonzero, select a "range" for examination |
39 | ** that is N' = min( n1, n2, N ). Average the distance from the |
40 | ** current position to the nearest N' requests on each side giving |
41 | ** d1 and d2. |
42 | ** Suppose the last decision was to move toward set 2, then the |
43 | ** current direction is toward set 2, and you will only switch to set |
44 | ** 1 if d1+R < d2 where R is r*(total number of cylinders), r in [0,1]. |
45 | ** |
46 | ** I extend this by applying only to the set of requests that all |
47 | ** share the same, highest priority level. |
48 | */ |
49 | |
50 | #ifndef _RF__RF_CVSCAN_H_ |
51 | #define _RF__RF_CVSCAN_H_ |
52 | |
53 | #include "rf_diskqueue.h" |
54 | |
55 | typedef enum RF_CvscanArmDir_e { |
56 | rf_cvscan_LEFT, |
57 | rf_cvscan_RIGHT |
58 | } RF_CvscanArmDir_t; |
59 | |
60 | typedef struct { |
61 | long ; /* CVSCAN param N */ |
62 | long ; /* CVSCAN param R */ |
63 | RF_CvscanArmDir_t ; |
64 | RF_SectorNum_t ; |
65 | int ; |
66 | RF_DiskQueueData_t *; |
67 | int ; |
68 | RF_DiskQueueData_t *; |
69 | int ; |
70 | RF_DiskQueueData_t *; |
71 | } ; |
72 | |
73 | void * |
74 | rf_CvscanCreate(RF_SectorCount_t sect_per_disk, |
75 | RF_AllocListElem_t * cl_list, RF_ShutdownList_t ** listp); |
76 | void rf_CvscanEnqueue(void *qptr, RF_DiskQueueData_t * req, int priority); |
77 | RF_DiskQueueData_t *rf_CvscanDequeue(void *qptr); |
78 | RF_DiskQueueData_t *rf_CvscanPeek(void *qptr); |
79 | int |
80 | rf_CvscanPromote(void *qptr, RF_StripeNum_t parityStripeID, |
81 | RF_ReconUnitNum_t which_ru); |
82 | |
83 | #endif /* !_RF__RF_CVSCAN_H_ */ |
84 | |