usr/src/sbin/newlfs/config.h

/*-
 * Copyright (c) 1991 The Regents of the University of California.
 * All rights reserved.
 *
 * %sccs.include.redist.c%
 *
 *      @(#)config.h    5.2 (Berkeley) %G%
 */

/*
 * The following two constants set the default block and fragment sizes.
 * Both constants must be a power of 2 and meet the following constraints:
 *      MINBSIZE <= DESBLKSIZE <= MAXBSIZE
 *      sectorsize <= DESFRAGSIZE <= DESBLKSIZE
 *      DESBLKSIZE / DESFRAGSIZE <= 8
 */
#define DFL_FRAGSIZE    1024
#define DFL_BLKSIZE     8192

/*
 * Cylinder groups may have up to many cylinders. The actual
 * number used depends upon how much information can be stored
 * on a single cylinder. The default is to use 16 cylinders
 * per group.
 */
#define DESCPG          16      /* desired fs_cpg */

/*
 * MINFREE gives the minimum acceptable percentage of file system
 * blocks which may be free. If the freelist drops below this level
 * only the superuser may continue to allocate blocks. This may
 * be set to 0 if no reserve of free blocks is deemed necessary,
 * however throughput drops by fifty percent if the file system
 * is run at between 90% and 100% full; thus the default value of
 * fs_minfree is 10%. With 10% free space, fragmentation is not a
 * problem, so we choose to optimize for time.
 */
#define MINFREE         10
#define DEFAULTOPT      FS_OPTTIME

/*
 * ROTDELAY gives the minimum number of milliseconds to initiate
 * another disk transfer on the same cylinder. It is used in
 * determining the rotationally optimal layout for disk blocks
 * within a file; the default of fs_rotdelay is 4ms.
 */
#define ROTDELAY        4

/*
 * MAXCONTIG sets the default for the maximum number of blocks
 * that may be allocated sequentially. Since UNIX drivers are
 * not capable of scheduling multi-block transfers, this defaults
 * to 1 (ie no contiguous blocks are allocated).
 */
#define MAXCONTIG       1

/*
 * MAXBLKPG determines the maximum number of data blocks which are
 * placed in a single cylinder group. The default is one indirect
 * block worth of data blocks.
 */
#define MAXBLKPG(bsize) ((bsize) / sizeof(daddr_t))

/*
 * Each file system has a number of inodes statically allocated.
 * We allocate one inode slot per NFPI fragments, expecting this
 * to be far more than we will ever need.
 */
#define NFPI            4

/*
 * For each cylinder we keep track of the availability of blocks at different
 * rotational positions, so that we can lay out the data to be picked
 * up with minimum rotational latency.  NRPOS is the default number of
 * rotational positions that we distinguish.  With NRPOS of 8 the resolution
 * of our summary information is 2ms for a typical 3600 rpm drive.
 */
#define NRPOS           8       /* number distinct rotational positions */

/*
 * The following constants set the default block and segment size for a log
 * structured file system.  Both must be powers of two and the segment size
 * must be a multiple of the block size.  We also set minimum block and segment
 * sizes.
 */
#define LFS_MINSEGSIZE          (128*1024)
#define DFL_LFSSEG              (1024 * 1024)
#define DFL_LFSSEG_SHIFT        20
#define DFL_LFSSEG_MASK         0xFFFFF

#define LFS_MINBLOCKSIZE        1024
#define DFL_LFSBLOCK            4096
#define DFL_LFSBLOCK_SHIFT      12
#define DFL_LFSBLOCK_MASK       0x7FF