[linux-2.6-block.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.

choice
	prompt "Decompressor parallelisation options"
	depends on SQUASHFS
	help
	  Squashfs now supports three parallelisation options for
	  decompression.  Each one exhibits various trade-offs between
	  decompression performance and CPU and memory usage.

	  If in doubt, select "Single threaded compression"

config SQUASHFS_DECOMP_SINGLE
	bool "Single threaded compression"
	help
	  Traditionally Squashfs has used single-threaded decompression.
	  Only one block (data or metadata) can be decompressed at any
	  one time.  This limits CPU and memory usage to a minimum.

config SQUASHFS_DECOMP_MULTI
	bool "Use multiple decompressors for parallel I/O"
	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.

	  This decompressor implementation uses up to two parallel
	  decompressors per core.  It dynamically allocates decompressors
	  on a demand basis.

config SQUASHFS_DECOMP_MULTI_PERCPU
	bool "Use percpu multiple decompressors for parallel I/O"
	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.

	  This decompressor implementation uses a maximum of one
	  decompressor per core.  It uses percpu variables to ensure
	  decompression is load-balanced across the cores.

endchoice

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_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
22635ec9 AD	1	config SQUASHFS
	2	tristate "SquashFS 4.0 - Squashed file system support"
	3	depends on BLOCK
22635ec9 AD	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
681ffe2e PL	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
4b676d2d	13	timestamps.
22635ec9 AD	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),
395cf969 PB	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.
22635ec9 AD	25
	26	If unsure, say N.
	27
d208383d PL	28	choice
	29	prompt "Decompressor parallelisation options"
	30	depends on SQUASHFS
	31	help
	32	Squashfs now supports three parallelisation options for
	33	decompression. Each one exhibits various trade-offs between
	34	decompression performance and CPU and memory usage.
	35
	36	If in doubt, select "Single threaded compression"
	37
	38	config SQUASHFS_DECOMP_SINGLE
	39	bool "Single threaded compression"
	40	help
	41	Traditionally Squashfs has used single-threaded decompression.
	42	Only one block (data or metadata) can be decompressed at any
	43	one time. This limits CPU and memory usage to a minimum.
	44
	45	config SQUASHFS_DECOMP_MULTI
	46	bool "Use multiple decompressors for parallel I/O"
	47	help
	48	By default Squashfs uses a single decompressor but it gives
	49	poor performance on parallel I/O workloads when using multiple CPU
	50	machines due to waiting on decompressor availability.
	51
	52	If you have a parallel I/O workload and your system has enough memory,
	53	using this option may improve overall I/O performance.
	54
	55	This decompressor implementation uses up to two parallel
	56	decompressors per core. It dynamically allocates decompressors
	57	on a demand basis.
	58
	59	config SQUASHFS_DECOMP_MULTI_PERCPU
	60	bool "Use percpu multiple decompressors for parallel I/O"
	61	help
	62	By default Squashfs uses a single decompressor but it gives
	63	poor performance on parallel I/O workloads when using multiple CPU
	64	machines due to waiting on decompressor availability.
	65
	66	This decompressor implementation uses a maximum of one
	67	decompressor per core. It uses percpu variables to ensure
	68	decompression is load-balanced across the cores.
	69
	70	endchoice
	71
637d5c9a	72	config SQUASHFS_XATTR
01e5b4e4 PL	73	bool "Squashfs XATTR support"
01e5b4e4 PL	74	depends on SQUASHFS
01e5b4e4 PL	75	help
	76	Saying Y here includes support for extended attributes (xattrs).
	77	Xattrs are name:value pairs associated with inodes by
	78	the kernel or by users (see the attr(5) manual page).
	79
	80	If unsure, say N.
	81
cc6d3497 PL	82	config SQUASHFS_ZLIB
	83	bool "Include support for ZLIB compressed file systems"
	84	depends on SQUASHFS
	85	select ZLIB_INFLATE
	86	default y
	87	help
	88	ZLIB compression is the standard compression used by Squashfs
	89	file systems. It offers a good trade-off between compression
	90	achieved and the amount of CPU time and memory necessary to
	91	compress and decompress.
	92
	93	If unsure, say Y.
	94
79cb8ced CJ	95	config SQUASHFS_LZO
	96	bool "Include support for LZO compressed file systems"
	97	depends on SQUASHFS
	98	select LZO_DECOMPRESS
4b676d2d PL	99	help
4b676d2d PL	100	Saying Y here includes support for reading Squashfs file systems
70f23fd6	101	compressed with LZO compression. LZO compression is mainly
4b676d2d PL	102	aimed at embedded systems with slower CPUs where the overheads
4b676d2d PL	103	of zlib are too high.
79cb8ced	104
4b676d2d PL	105	LZO is not the standard compression used in Squashfs and so most
4b676d2d PL	106	file systems will be readable without selecting this option.
22635ec9	107
4b676d2d PL	108	If unsure, say N.
4b676d2d PL	109
7a43ae52 PL	110	config SQUASHFS_XZ
	111	bool "Include support for XZ compressed file systems"
	112	depends on SQUASHFS
	113	select XZ_DEC
	114	help
	115	Saying Y here includes support for reading Squashfs file systems
70f23fd6	116	compressed with XZ compression. XZ gives better compression than
7a43ae52 PL	117	the default zlib compression, at the expense of greater CPU and
	118	memory overhead.
	119
	120	XZ is not the standard compression used in Squashfs and so most
	121	file systems will be readable without selecting this option.
	122
	123	If unsure, say N.
	124
7657cacf PL	125	config SQUASHFS_4K_DEVBLK_SIZE
	126	bool "Use 4K device block size?"
	127	depends on SQUASHFS
	128	help
	129	By default Squashfs sets the dev block size (sb_min_blocksize)
	130	to 1K or the smallest block size supported by the block device
	131	(if larger). This, because blocks are packed together and
	132	unaligned in Squashfs, should reduce latency.
	133
	134	This, however, gives poor performance on MTD NAND devices where
	135	the optimal I/O size is 4K (even though the devices can support
	136	smaller block sizes).
	137
	138	Using a 4K device block size may also improve overall I/O
	139	performance for some file access patterns (e.g. sequential
	140	accesses of files in filesystem order) on all media.
	141
	142	Setting this option will force Squashfs to use a 4K device block
	143	size by default.
	144
	145	If unsure, say N.
	146
4b676d2d PL	147	config SQUASHFS_EMBEDDED
4b676d2d PL	148	bool "Additional option for memory-constrained systems"
22635ec9	149	depends on SQUASHFS
22635ec9 AD	150	help
	151	Saying Y here allows you to specify cache size.
	152
	153	If unsure, say N.
	154
	155	config SQUASHFS_FRAGMENT_CACHE_SIZE
	156	int "Number of fragments cached" if SQUASHFS_EMBEDDED
	157	depends on SQUASHFS
	158	default "3"
	159	help
	160	By default SquashFS caches the last 3 fragments read from
	161	the filesystem. Increasing this amount may mean SquashFS
	162	has to re-read fragments less often from disk, at the expense
	163	of extra system memory. Decreasing this amount will mean
	164	SquashFS uses less memory at the expense of extra reads from disk.
	165
	166	Note there must be at least one cached fragment. Anything
	167	much more than three will probably not make much difference.