1eecf8e491
out-dated comments, and other unneeded stuff. This helps prepare for cleaning up the rest of the code, and adding new functionality. No functional changes to the kernel code in this commit.
83 lines
2.9 KiB
C
83 lines
2.9 KiB
C
/* $NetBSD: rf_cvscan.h,v 1.2 1999/01/26 02:33:51 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 *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 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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