FreeBSD/Linux Kernel Cross Reference
sys/dev/raidframe/rf_cvscan.h

     /*      $NetBSD: rf_cvscan.h,v 1.4 2002/09/21 00:37:14 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  Software.Distribution@CS.CMU.EDU
     *  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);
    RF_DiskQueueData_t *rf_CvscanPeek(void *qptr);
    int 
    rf_CvscanPromote(void *qptr, RF_StripeNum_t parityStripeID,
        RF_ReconUnitNum_t which_ru);
    
    #endif                          /* !_RF__RF_CVSCAN_H_ */

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