config.h

早期freebsd实现

/*-
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)config.h	8.2 (Berkeley) 4/22/94
 */

/*
 * The first boot and super blocks are given in absolute disk addresses.
 * The byte-offset forms are preferred, as they don't imply a sector size.
 */
#define BBSIZE		8192
#define SBSIZE		8192

/*
 * 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

/*
 * Preference for optimization.
 */
#define FS_OPTTIME	0	/* minimize allocation time */
#define FS_OPTSPACE	1	/* minimize disk fragmentation */


/*
 * 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		(64*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	0xFFF