/* $NetBSD: rf_cvscan.h,v 1.7 2021/07/27 03:09:26 oster Exp $ */
/*
* Copyright (c) 1995 Carnegie-Mellon University.
* All rights reserved.
*
* Author: Mark Holland
*
* Permission to use, copy, modify and distribute this software and
* its documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or
[email protected]
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*/
/*
** Disk scheduling by CVSCAN( N, r )
**
** Given a set of requests, partition them into one set on each
** side of the current arm position. The trick is to pick which
** side you are going to service next; once a side is picked you will
** service the closest request.
** Let there be n1 requests on one side and n2 requests on the other
** side. If one of n1 or n2 is zero, select the other side.
** If both n1 and n2 are nonzero, select a "range" for examination
** that is N' = min( n1, n2, N ). Average the distance from the
** current position to the nearest N' requests on each side giving
** d1 and d2.
** Suppose the last decision was to move toward set 2, then the
** current direction is toward set 2, and you will only switch to set
** 1 if d1+R < d2 where R is r*(total number of cylinders), r in [0,1].
**
** I extend this by applying only to the set of requests that all
** share the same, highest priority level.
*/
#ifndef _RF__RF_CVSCAN_H_
#define _RF__RF_CVSCAN_H_
#include "rf_diskqueue.h"
typedef enum RF_CvscanArmDir_e {
rf_cvscan_LEFT,
rf_cvscan_RIGHT
} RF_CvscanArmDir_t;
typedef struct RF_CvscanHeader_s {
long range_for_avg; /* CVSCAN param N */
long change_penalty; /* CVSCAN param R */
RF_CvscanArmDir_t direction;
RF_SectorNum_t cur_block;
int nxt_priority;
RF_DiskQueueData_t *left;
int left_cnt;
RF_DiskQueueData_t *right;
int right_cnt;
RF_DiskQueueData_t *burner;
} RF_CvscanHeader_t;
void *
rf_CvscanCreate(RF_SectorCount_t sect_per_disk,
RF_AllocListElem_t * cl_list, RF_ShutdownList_t ** listp);
void rf_CvscanEnqueue(void *qptr, RF_DiskQueueData_t * req, int priority);
RF_DiskQueueData_t *rf_CvscanDequeue(void *qptr);
int
rf_CvscanPromote(void *qptr, RF_StripeNum_t parityStripeID,
RF_ReconUnitNum_t which_ru);
#endif /* !_RF__RF_CVSCAN_H_ */
