sys/dev/raidframe/rf_cvscan.h

   1 /*      $NetBSD: rf_cvscan.h,v 1.4.6.1 2005/03/04 16:50:05 skrll 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 RF_DiskQueueData_t *rf_CvscanPeek(void *qptr);
  79 int
  80 rf_CvscanPromote(void *qptr, RF_StripeNum_t parityStripeID,
  81     RF_ReconUnitNum_t which_ru);
  82
  83 #endif                          /* !_RF__RF_CVSCAN_H_ */