[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.

choice
	prompt "File decompression options"
	depends on SQUASHFS
	help
	  Squashfs now supports two options for decompressing file
	  data.  Traditionally Squashfs has decompressed into an
	  intermediate buffer and then memcopied it into the page cache.
	  Squashfs now supports the ability to decompress directly into
	  the page cache.

	  If unsure, select "Decompress file data into an intermediate buffer"

config SQUASHFS_FILE_CACHE
	bool "Decompress file data into an intermediate buffer"
	help
	  Decompress file data into an intermediate buffer and then
	  memcopy it into the page cache.

config SQUASHFS_FILE_DIRECT
	bool "Decompress files directly into the page cache"
	help
	  Directly decompress file data into the page cache.
	  Doing so can significantly improve performance because
	  it eliminates a memcpy and it also removes the lock contention
	  on the single buffer.

endchoice

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
0d455c12 PL	28	choice
	29	prompt "File decompression options"
	30	depends on SQUASHFS
	31	help
	32	Squashfs now supports two options for decompressing file
	33	data. Traditionally Squashfs has decompressed into an
	34	intermediate buffer and then memcopied it into the page cache.
	35	Squashfs now supports the ability to decompress directly into
	36	the page cache.
	37
	38	If unsure, select "Decompress file data into an intermediate buffer"
	39
	40	config SQUASHFS_FILE_CACHE
	41	bool "Decompress file data into an intermediate buffer"
	42	help
	43	Decompress file data into an intermediate buffer and then
	44	memcopy it into the page cache.
	45
	46	config SQUASHFS_FILE_DIRECT
	47	bool "Decompress files directly into the page cache"
	48	help
	49	Directly decompress file data into the page cache.
	50	Doing so can significantly improve performance because
	51	it eliminates a memcpy and it also removes the lock contention
	52	on the single buffer.
	53
	54	endchoice
	55
d208383d PL	56	choice
	57	prompt "Decompressor parallelisation options"
	58	depends on SQUASHFS
	59	help
	60	Squashfs now supports three parallelisation options for
	61	decompression. Each one exhibits various trade-offs between
	62	decompression performance and CPU and memory usage.
	63
	64	If in doubt, select "Single threaded compression"
	65
	66	config SQUASHFS_DECOMP_SINGLE
	67	bool "Single threaded compression"
	68	help
	69	Traditionally Squashfs has used single-threaded decompression.
	70	Only one block (data or metadata) can be decompressed at any
	71	one time. This limits CPU and memory usage to a minimum.
	72
	73	config SQUASHFS_DECOMP_MULTI
	74	bool "Use multiple decompressors for parallel I/O"
	75	help
	76	By default Squashfs uses a single decompressor but it gives
	77	poor performance on parallel I/O workloads when using multiple CPU
	78	machines due to waiting on decompressor availability.
	79
	80	If you have a parallel I/O workload and your system has enough memory,
	81	using this option may improve overall I/O performance.
	82
	83	This decompressor implementation uses up to two parallel
	84	decompressors per core. It dynamically allocates decompressors
	85	on a demand basis.
	86
	87	config SQUASHFS_DECOMP_MULTI_PERCPU
	88	bool "Use percpu multiple decompressors for parallel I/O"
	89	help
	90	By default Squashfs uses a single decompressor but it gives
	91	poor performance on parallel I/O workloads when using multiple CPU
	92	machines due to waiting on decompressor availability.
	93
	94	This decompressor implementation uses a maximum of one
	95	decompressor per core. It uses percpu variables to ensure
	96	decompression is load-balanced across the cores.
	97
	98	endchoice
	99
637d5c9a	100	config SQUASHFS_XATTR
01e5b4e4 PL	101	bool "Squashfs XATTR support"
01e5b4e4 PL	102	depends on SQUASHFS
01e5b4e4 PL	103	help
	104	Saying Y here includes support for extended attributes (xattrs).
	105	Xattrs are name:value pairs associated with inodes by
	106	the kernel or by users (see the attr(5) manual page).
	107
	108	If unsure, say N.
	109
cc6d3497 PL	110	config SQUASHFS_ZLIB
	111	bool "Include support for ZLIB compressed file systems"
	112	depends on SQUASHFS
	113	select ZLIB_INFLATE
	114	default y
	115	help
	116	ZLIB compression is the standard compression used by Squashfs
	117	file systems. It offers a good trade-off between compression
	118	achieved and the amount of CPU time and memory necessary to
	119	compress and decompress.
	120
	121	If unsure, say Y.
	122
79cb8ced CJ	123	config SQUASHFS_LZO
	124	bool "Include support for LZO compressed file systems"
	125	depends on SQUASHFS
	126	select LZO_DECOMPRESS
4b676d2d PL	127	help
4b676d2d PL	128	Saying Y here includes support for reading Squashfs file systems
70f23fd6	129	compressed with LZO compression. LZO compression is mainly
4b676d2d PL	130	aimed at embedded systems with slower CPUs where the overheads
4b676d2d PL	131	of zlib are too high.
79cb8ced	132
4b676d2d PL	133	LZO is not the standard compression used in Squashfs and so most
4b676d2d PL	134	file systems will be readable without selecting this option.
22635ec9	135
4b676d2d PL	136	If unsure, say N.
4b676d2d PL	137
7a43ae52 PL	138	config SQUASHFS_XZ
	139	bool "Include support for XZ compressed file systems"
	140	depends on SQUASHFS
	141	select XZ_DEC
	142	help
	143	Saying Y here includes support for reading Squashfs file systems
70f23fd6	144	compressed with XZ compression. XZ gives better compression than
7a43ae52 PL	145	the default zlib compression, at the expense of greater CPU and
	146	memory overhead.
	147
	148	XZ is not the standard compression used in Squashfs and so most
	149	file systems will be readable without selecting this option.
	150
	151	If unsure, say N.
	152
7657cacf PL	153	config SQUASHFS_4K_DEVBLK_SIZE
	154	bool "Use 4K device block size?"
	155	depends on SQUASHFS
	156	help
	157	By default Squashfs sets the dev block size (sb_min_blocksize)
	158	to 1K or the smallest block size supported by the block device
	159	(if larger). This, because blocks are packed together and
	160	unaligned in Squashfs, should reduce latency.
	161
	162	This, however, gives poor performance on MTD NAND devices where
	163	the optimal I/O size is 4K (even though the devices can support
	164	smaller block sizes).
	165
	166	Using a 4K device block size may also improve overall I/O
	167	performance for some file access patterns (e.g. sequential
	168	accesses of files in filesystem order) on all media.
	169
	170	Setting this option will force Squashfs to use a 4K device block
	171	size by default.
	172
	173	If unsure, say N.
	174
4b676d2d PL	175	config SQUASHFS_EMBEDDED
4b676d2d PL	176	bool "Additional option for memory-constrained systems"
22635ec9	177	depends on SQUASHFS
22635ec9 AD	178	help
	179	Saying Y here allows you to specify cache size.
	180
	181	If unsure, say N.
	182
	183	config SQUASHFS_FRAGMENT_CACHE_SIZE
	184	int "Number of fragments cached" if SQUASHFS_EMBEDDED
	185	depends on SQUASHFS
	186	default "3"
	187	help
	188	By default SquashFS caches the last 3 fragments read from
	189	the filesystem. Increasing this amount may mean SquashFS
	190	has to re-read fragments less often from disk, at the expense
	191	of extra system memory. Decreasing this amount will mean
	192	SquashFS uses less memory at the expense of extra reads from disk.
	193
	194	Note there must be at least one cached fragment. Anything
	195	much more than three will probably not make much difference.