85 lines
2.9 KiB
C
85 lines
2.9 KiB
C
/* $NetBSD: rf_cvscan.h,v 1.3 1999/02/05 00:06:07 oster Exp $ */
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/*
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* Copyright (c) 1995 Carnegie-Mellon University.
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* All rights reserved.
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*
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* Author: Mark Holland
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*
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* Permission to use, copy, modify and distribute this software and
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* its documentation is hereby granted, provided that both the copyright
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* notice and this permission notice appear in all copies of the
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* software, derivative works or modified versions, and any portions
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* thereof, and that both notices appear in supporting documentation.
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*
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* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
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* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
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* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
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*
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* Carnegie Mellon requests users of this software to return to
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*
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* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
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* School of Computer Science
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* Carnegie Mellon University
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* Pittsburgh PA 15213-3890
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*
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* any improvements or extensions that they make and grant Carnegie the
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* rights to redistribute these changes.
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*/
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/*
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** Disk scheduling by CVSCAN( N, r )
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**
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** Given a set of requests, partition them into one set on each
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** side of the current arm position. The trick is to pick which
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** side you are going to service next; once a side is picked you will
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** service the closest request.
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** Let there be n1 requests on one side and n2 requests on the other
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** side. If one of n1 or n2 is zero, select the other side.
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** If both n1 and n2 are nonzero, select a "range" for examination
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** that is N' = min( n1, n2, N ). Average the distance from the
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** current position to the nearest N' requests on each side giving
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** d1 and d2.
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** Suppose the last decision was to move toward set 2, then the
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** current direction is toward set 2, and you will only switch to set
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** 1 if d1+R < d2 where R is r*(total number of cylinders), r in [0,1].
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**
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** I extend this by applying only to the set of requests that all
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** share the same, highest priority level.
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*/
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#ifndef _RF__RF_CVSCAN_H_
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#define _RF__RF_CVSCAN_H_
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#include "rf_diskqueue.h"
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typedef enum RF_CvscanArmDir_e {
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rf_cvscan_LEFT,
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rf_cvscan_RIGHT
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} RF_CvscanArmDir_t;
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typedef struct RF_CvscanHeader_s {
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long range_for_avg; /* CVSCAN param N */
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long change_penalty; /* CVSCAN param R */
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RF_CvscanArmDir_t direction;
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RF_SectorNum_t cur_block;
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int nxt_priority;
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RF_DiskQueueData_t *left;
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int left_cnt;
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RF_DiskQueueData_t *right;
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int right_cnt;
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RF_DiskQueueData_t *burner;
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} RF_CvscanHeader_t;
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int rf_CvscanConfigure(void);
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void *
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rf_CvscanCreate(RF_SectorCount_t sect_per_disk,
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RF_AllocListElem_t * cl_list, RF_ShutdownList_t ** listp);
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void rf_CvscanEnqueue(void *qptr, RF_DiskQueueData_t * req, int priority);
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RF_DiskQueueData_t *rf_CvscanDequeue(void *qptr);
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RF_DiskQueueData_t *rf_CvscanPeek(void *qptr);
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int
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rf_CvscanPromote(void *qptr, RF_StripeNum_t parityStripeID,
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RF_ReconUnitNum_t which_ru);
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#endif /* !_RF__RF_CVSCAN_H_ */
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