[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 "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_LZ4
	bool "Include support for LZ4 compressed file systems"
	depends on SQUASHFS
	select LZ4_DECOMPRESS
	help
	  Saying Y here includes support for reading Squashfs file systems
	  compressed with LZ4 compression.  LZ4 compression is mainly
	  aimed at embedded systems with slower CPUs where the overheads
	  of zlib are too high.

	  LZ4 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_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_ZSTD
	bool "Include support for ZSTD compressed file systems"
	depends on SQUASHFS
	select ZSTD_DECOMPRESS
	help
	  Saying Y here includes support for reading Squashfs file systems
	  compressed with ZSTD compression.  ZSTD gives better compression than
	  the default ZLIB compression, while using less CPU.

	  ZSTD 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	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
	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
	100	config SQUASHFS_XATTR
	101	bool "Squashfs XATTR support"
	102	depends on SQUASHFS
	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
	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
	123	config SQUASHFS_LZ4
	124	bool "Include support for LZ4 compressed file systems"
	125	depends on SQUASHFS
	126	select LZ4_DECOMPRESS
	127	help
	128	Saying Y here includes support for reading Squashfs file systems
	129	compressed with LZ4 compression. LZ4 compression is mainly
	130	aimed at embedded systems with slower CPUs where the overheads
	131	of zlib are too high.
	132
	133	LZ4 is not the standard compression used in Squashfs and so most
	134	file systems will be readable without selecting this option.
	135
	136	If unsure, say N.
	137
	138	config SQUASHFS_LZO
	139	bool "Include support for LZO compressed file systems"
	140	depends on SQUASHFS
	141	select LZO_DECOMPRESS
	142	help
	143	Saying Y here includes support for reading Squashfs file systems
	144	compressed with LZO compression. LZO compression is mainly
	145	aimed at embedded systems with slower CPUs where the overheads
	146	of zlib are too high.
	147
	148	LZO 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
	153	config SQUASHFS_XZ
	154	bool "Include support for XZ compressed file systems"
	155	depends on SQUASHFS
	156	select XZ_DEC
	157	help
	158	Saying Y here includes support for reading Squashfs file systems
	159	compressed with XZ compression. XZ gives better compression than
	160	the default zlib compression, at the expense of greater CPU and
	161	memory overhead.
	162
	163	XZ is not the standard compression used in Squashfs and so most
	164	file systems will be readable without selecting this option.
	165
	166	If unsure, say N.
	167
	168	config SQUASHFS_ZSTD
	169	bool "Include support for ZSTD compressed file systems"
	170	depends on SQUASHFS
	171	select ZSTD_DECOMPRESS
	172	help
	173	Saying Y here includes support for reading Squashfs file systems
	174	compressed with ZSTD compression. ZSTD gives better compression than
	175	the default ZLIB compression, while using less CPU.
	176
	177	ZSTD is not the standard compression used in Squashfs and so most
	178	file systems will be readable without selecting this option.
	179
	180	If unsure, say N.
	181
	182	config SQUASHFS_4K_DEVBLK_SIZE
	183	bool "Use 4K device block size?"
	184	depends on SQUASHFS
	185	help
	186	By default Squashfs sets the dev block size (sb_min_blocksize)
	187	to 1K or the smallest block size supported by the block device
	188	(if larger). This, because blocks are packed together and
	189	unaligned in Squashfs, should reduce latency.
	190
	191	This, however, gives poor performance on MTD NAND devices where
	192	the optimal I/O size is 4K (even though the devices can support
	193	smaller block sizes).
	194
	195	Using a 4K device block size may also improve overall I/O
	196	performance for some file access patterns (e.g. sequential
	197	accesses of files in filesystem order) on all media.
	198
	199	Setting this option will force Squashfs to use a 4K device block
	200	size by default.
	201
	202	If unsure, say N.
	203
	204	config SQUASHFS_EMBEDDED
	205	bool "Additional option for memory-constrained systems"
	206	depends on SQUASHFS
	207	help
	208	Saying Y here allows you to specify cache size.
	209
	210	If unsure, say N.
	211
	212	config SQUASHFS_FRAGMENT_CACHE_SIZE
	213	int "Number of fragments cached" if SQUASHFS_EMBEDDED
	214	depends on SQUASHFS
	215	default "3"
	216	help
	217	By default SquashFS caches the last 3 fragments read from
	218	the filesystem. Increasing this amount may mean SquashFS
	219	has to re-read fragments less often from disk, at the expense
	220	of extra system memory. Decreasing this amount will mean
	221	SquashFS uses less memory at the expense of extra reads from disk.
	222
	223	Note there must be at least one cached fragment. Anything
	224	much more than three will probably not make much difference.