fs/squashfs/Kconfig

   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_4K_DEVBLK_SIZE
 169         bool "Use 4K device block size?"
 170         depends on SQUASHFS
 171         help
 172           By default Squashfs sets the dev block size (sb_min_blocksize)
 173           to 1K or the smallest block size supported by the block device
 174           (if larger).  This, because blocks are packed together and
 175           unaligned in Squashfs, should reduce latency.
 176
 177           This, however, gives poor performance on MTD NAND devices where
 178           the optimal I/O size is 4K (even though the devices can support
 179           smaller block sizes).
 180
 181           Using a 4K device block size may also improve overall I/O
 182           performance for some file access patterns (e.g. sequential
 183           accesses of files in filesystem order) on all media.
 184
 185           Setting this option will force Squashfs to use a 4K device block
 186           size by default.
 187
 188           If unsure, say N.
 189
 190 config SQUASHFS_EMBEDDED
 191         bool "Additional option for memory-constrained systems"
 192         depends on SQUASHFS
 193         help
 194           Saying Y here allows you to specify cache size.
 195
 196           If unsure, say N.
 197
 198 config SQUASHFS_FRAGMENT_CACHE_SIZE
 199         int "Number of fragments cached" if SQUASHFS_EMBEDDED
 200         depends on SQUASHFS
 201         default "3"
 202         help
 203           By default SquashFS caches the last 3 fragments read from
 204           the filesystem.  Increasing this amount may mean SquashFS
 205           has to re-read fragments less often from disk, at the expense
 206           of extra system memory.  Decreasing this amount will mean
 207           SquashFS uses less memory at the expense of extra reads from disk.
 208
 209           Note there must be at least one cached fragment.  Anything
 210           much more than three will probably not make much difference.