1 /*        $NetBSD: rf_cvscan.h,v 1.7 2021/07/27 03:09:26 oster 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 RF_CvscanHeader_s {
61           long    range_for_avg;        /* CVSCAN param N */
62           long    change_penalty;       /* CVSCAN param R */
63           RF_CvscanArmDir_t direction;
64           RF_SectorNum_t cur_block;
65           int     nxt_priority;
66           RF_DiskQueueData_t *left;
67           int     left_cnt;
68           RF_DiskQueueData_t *right;
69           int     right_cnt;
70           RF_DiskQueueData_t *burner;
71 }       RF_CvscanHeader_t;
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 int
79 rf_CvscanPromote(void *qptr, RF_StripeNum_t parityStripeID,
80     RF_ReconUnitNum_t which_ru);
81 
82 #endif                                  /* !_RF__RF_CVSCAN_H_ */
83