[deliverable/linux.git] / fs / squashfs / Kconfig

config SQUASHFS
	tristate "SquashFS 4.0 - Squashed file system support"
	depends on BLOCK
	help
	  Saying Y here includes support for SquashFS 4.0 (a Compressed
	  Read-Only File System).  Squashfs is a highly compressed read-only
	  filesystem for Linux.  It uses zlib, lzo or xz compression to
	  compress both files, inodes and directories.  Inodes in the system
	  are very small and all blocks are packed to minimise data overhead.
	  Block sizes greater than 4K are supported up to a maximum of 1 Mbytes
	  (default block size 128K).  SquashFS 4.0 supports 64 bit filesystems
	  and files (larger than 4GB), full uid/gid information, hard links and
	  timestamps.

	  Squashfs is intended for general read-only filesystem use, for
	  archival use (i.e. in cases where a .tar.gz file may be used), and in
	  embedded systems where low overhead is needed.  Further information
	  and tools are available from http://squashfs.sourceforge.net.

	  If you want to compile this as a module ( = code which can be
	  inserted in and removed from the running kernel whenever you want),
	  say M here.  The module will be called squashfs.  Note that the root
	  file system (the one containing the directory /) cannot be compiled
	  as a module.

	  If unsure, say N.

config SQUASHFS_XATTR
	bool "Squashfs XATTR support"
	depends on SQUASHFS
	help
	  Saying Y here includes support for extended attributes (xattrs).
	  Xattrs are name:value pairs associated with inodes by
	  the kernel or by users (see the attr(5) manual page).

	  If unsure, say N.

config SQUASHFS_ZLIB
	bool "Include support for ZLIB compressed file systems"
	depends on SQUASHFS
	select ZLIB_INFLATE
	default y
	help
	  ZLIB compression is the standard compression used by Squashfs
	  file systems.  It offers a good trade-off between compression
	  achieved and the amount of CPU time and memory necessary to
	  compress and decompress.

	  If unsure, say Y.

config SQUASHFS_LZO
	bool "Include support for LZO compressed file systems"
	depends on SQUASHFS
	select LZO_DECOMPRESS
	help
	  Saying Y here includes support for reading Squashfs file systems
	  compressed with LZO compression.  LZO compression is mainly
	  aimed at embedded systems with slower CPUs where the overheads
	  of zlib are too high.

	  LZO is not the standard compression used in Squashfs and so most
	  file systems will be readable without selecting this option.

	  If unsure, say N.

config SQUASHFS_MULTI_DECOMPRESSOR
	bool "Use multiple decompressors for handling parallel I/O"
	depends on SQUASHFS
	help
	  By default Squashfs uses a single decompressor but it gives
	  poor performance on parallel I/O workloads when using multiple CPU
	  machines due to waiting on decompressor availability.

	  If you have a parallel I/O workload and your system has enough memory,
	  using this option may improve overall I/O performance.

	  If unsure, say N.

config SQUASHFS_XZ
	bool "Include support for XZ compressed file systems"
	depends on SQUASHFS
	select XZ_DEC
	help
	  Saying Y here includes support for reading Squashfs file systems
	  compressed with XZ compression.  XZ gives better compression than
	  the default zlib compression, at the expense of greater CPU and
	  memory overhead.

	  XZ is not the standard compression used in Squashfs and so most
	  file systems will be readable without selecting this option.

	  If unsure, say N.

config SQUASHFS_4K_DEVBLK_SIZE
	bool "Use 4K device block size?"
	depends on SQUASHFS
	help
	  By default Squashfs sets the dev block size (sb_min_blocksize)
	  to 1K or the smallest block size supported by the block device
	  (if larger).  This, because blocks are packed together and
	  unaligned in Squashfs, should reduce latency.

	  This, however, gives poor performance on MTD NAND devices where
	  the optimal I/O size is 4K (even though the devices can support
	  smaller block sizes).

	  Using a 4K device block size may also improve overall I/O
	  performance for some file access patterns (e.g. sequential
	  accesses of files in filesystem order) on all media.

	  Setting this option will force Squashfs to use a 4K device block
	  size by default.

	  If unsure, say N.

config SQUASHFS_EMBEDDED
	bool "Additional option for memory-constrained systems"
	depends on SQUASHFS
	help
	  Saying Y here allows you to specify cache size.

	  If unsure, say N.

config SQUASHFS_FRAGMENT_CACHE_SIZE
	int "Number of fragments cached" if SQUASHFS_EMBEDDED
	depends on SQUASHFS
	default "3"
	help
	  By default SquashFS caches the last 3 fragments read from
	  the filesystem.  Increasing this amount may mean SquashFS
	  has to re-read fragments less often from disk, at the expense
	  of extra system memory.  Decreasing this amount will mean
	  SquashFS uses less memory at the expense of extra reads from disk.

	  Note there must be at least one cached fragment.  Anything
	  much more than three will probably not make much difference.
Commit	Line	Data
	1	config SQUASHFS
	2	tristate "SquashFS 4.0 - Squashed file system support"
	3	depends on BLOCK
	4	help
	5	Saying Y here includes support for SquashFS 4.0 (a Compressed
	6	Read-Only File System). Squashfs is a highly compressed read-only
	7	filesystem for Linux. It uses zlib, lzo or xz compression to
	8	compress both files, inodes and directories. Inodes in the system
	9	are very small and all blocks are packed to minimise data overhead.
	10	Block sizes greater than 4K are supported up to a maximum of 1 Mbytes
	11	(default block size 128K). SquashFS 4.0 supports 64 bit filesystems
	12	and files (larger than 4GB), full uid/gid information, hard links and
	13	timestamps.
	14
	15	Squashfs is intended for general read-only filesystem use, for
	16	archival use (i.e. in cases where a .tar.gz file may be used), and in
	17	embedded systems where low overhead is needed. Further information
	18	and tools are available from http://squashfs.sourceforge.net.
	19
	20	If you want to compile this as a module ( = code which can be
	21	inserted in and removed from the running kernel whenever you want),
	22	say M here. The module will be called squashfs. Note that the root
	23	file system (the one containing the directory /) cannot be compiled
	24	as a module.
	25
	26	If unsure, say N.
	27
	28	config SQUASHFS_XATTR
	29	bool "Squashfs XATTR support"
	30	depends on SQUASHFS
	31	help
	32	Saying Y here includes support for extended attributes (xattrs).
	33	Xattrs are name:value pairs associated with inodes by
	34	the kernel or by users (see the attr(5) manual page).
	35
	36	If unsure, say N.
	37
	38	config SQUASHFS_ZLIB
	39	bool "Include support for ZLIB compressed file systems"
	40	depends on SQUASHFS
	41	select ZLIB_INFLATE
	42	default y
	43	help
	44	ZLIB compression is the standard compression used by Squashfs
	45	file systems. It offers a good trade-off between compression
	46	achieved and the amount of CPU time and memory necessary to
	47	compress and decompress.
	48
	49	If unsure, say Y.
	50
	51	config SQUASHFS_LZO
	52	bool "Include support for LZO compressed file systems"
	53	depends on SQUASHFS
	54	select LZO_DECOMPRESS
	55	help
	56	Saying Y here includes support for reading Squashfs file systems
	57	compressed with LZO compression. LZO compression is mainly
	58	aimed at embedded systems with slower CPUs where the overheads
	59	of zlib are too high.
	60
	61	LZO is not the standard compression used in Squashfs and so most
	62	file systems will be readable without selecting this option.
	63
	64	If unsure, say N.
	65
	66	config SQUASHFS_MULTI_DECOMPRESSOR
	67	bool "Use multiple decompressors for handling parallel I/O"
	68	depends on SQUASHFS
	69	help
	70	By default Squashfs uses a single decompressor but it gives
	71	poor performance on parallel I/O workloads when using multiple CPU
	72	machines due to waiting on decompressor availability.
	73
	74	If you have a parallel I/O workload and your system has enough memory,
	75	using this option may improve overall I/O performance.
	76
	77	If unsure, say N.
	78
	79	config SQUASHFS_XZ
	80	bool "Include support for XZ compressed file systems"
	81	depends on SQUASHFS
	82	select XZ_DEC
	83	help
	84	Saying Y here includes support for reading Squashfs file systems
	85	compressed with XZ compression. XZ gives better compression than
	86	the default zlib compression, at the expense of greater CPU and
	87	memory overhead.
	88
	89	XZ is not the standard compression used in Squashfs and so most
	90	file systems will be readable without selecting this option.
	91
	92	If unsure, say N.
	93
	94	config SQUASHFS_4K_DEVBLK_SIZE
	95	bool "Use 4K device block size?"
	96	depends on SQUASHFS
	97	help
	98	By default Squashfs sets the dev block size (sb_min_blocksize)
	99	to 1K or the smallest block size supported by the block device
	100	(if larger). This, because blocks are packed together and
	101	unaligned in Squashfs, should reduce latency.
	102
	103	This, however, gives poor performance on MTD NAND devices where
	104	the optimal I/O size is 4K (even though the devices can support
	105	smaller block sizes).
	106
	107	Using a 4K device block size may also improve overall I/O
	108	performance for some file access patterns (e.g. sequential
	109	accesses of files in filesystem order) on all media.
	110
	111	Setting this option will force Squashfs to use a 4K device block
	112	size by default.
	113
	114	If unsure, say N.
	115
	116	config SQUASHFS_EMBEDDED
	117	bool "Additional option for memory-constrained systems"
	118	depends on SQUASHFS
	119	help
	120	Saying Y here allows you to specify cache size.
	121
	122	If unsure, say N.
	123
	124	config SQUASHFS_FRAGMENT_CACHE_SIZE
	125	int "Number of fragments cached" if SQUASHFS_EMBEDDED
	126	depends on SQUASHFS
	127	default "3"
	128	help
	129	By default SquashFS caches the last 3 fragments read from
	130	the filesystem. Increasing this amount may mean SquashFS
	131	has to re-read fragments less often from disk, at the expense
	132	of extra system memory. Decreasing this amount will mean
	133	SquashFS uses less memory at the expense of extra reads from disk.
	134
	135	Note there must be at least one cached fragment. Anything
	136	much more than three will probably not make much difference.