1config 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 28choice 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 38config 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 45config 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 59config 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 70endchoice 71 72config SQUASHFS_XATTR 73 bool "Squashfs XATTR support" 74 depends on SQUASHFS 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 82config 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 95config SQUASHFS_LZ4 96 bool "Include support for LZ4 compressed file systems" 97 depends on SQUASHFS 98 select LZ4_DECOMPRESS 99 help 100 Saying Y here includes support for reading Squashfs file systems 101 compressed with LZ4 compression. LZ4 compression is mainly 102 aimed at embedded systems with slower CPUs where the overheads 103 of zlib are too high. 104 105 LZ4 is not the standard compression used in Squashfs and so most 106 file systems will be readable without selecting this option. 107 108 If unsure, say N. 109 110config SQUASHFS_LZO 111 bool "Include support for LZO compressed file systems" 112 depends on SQUASHFS 113 select LZO_DECOMPRESS 114 help 115 Saying Y here includes support for reading Squashfs file systems 116 compressed with LZO compression. LZO compression is mainly 117 aimed at embedded systems with slower CPUs where the overheads 118 of zlib are too high. 119 120 LZO 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 125config SQUASHFS_XZ 126 bool "Include support for XZ compressed file systems" 127 depends on SQUASHFS 128 select XZ_DEC 129 help 130 Saying Y here includes support for reading Squashfs file systems 131 compressed with XZ compression. XZ gives better compression than 132 the default zlib compression, at the expense of greater CPU and 133 memory overhead. 134 135 XZ is not the standard compression used in Squashfs and so most 136 file systems will be readable without selecting this option. 137 138 If unsure, say N. 139 140config SQUASHFS_4K_DEVBLK_SIZE 141 bool "Use 4K device block size?" 142 depends on SQUASHFS 143 help 144 By default Squashfs sets the dev block size (sb_min_blocksize) 145 to 1K or the smallest block size supported by the block device 146 (if larger). This, because blocks are packed together and 147 unaligned in Squashfs, should reduce latency. 148 149 This, however, gives poor performance on MTD NAND devices where 150 the optimal I/O size is 4K (even though the devices can support 151 smaller block sizes). 152 153 Using a 4K device block size may also improve overall I/O 154 performance for some file access patterns (e.g. sequential 155 accesses of files in filesystem order) on all media. 156 157 Setting this option will force Squashfs to use a 4K device block 158 size by default. 159 160 If unsure, say N. 161 162config SQUASHFS_EMBEDDED 163 bool "Additional option for memory-constrained systems" 164 depends on SQUASHFS 165 help 166 Saying Y here allows you to specify cache size. 167 168 If unsure, say N. 169 170config SQUASHFS_FRAGMENT_CACHE_SIZE 171 int "Number of fragments cached" if SQUASHFS_EMBEDDED 172 depends on SQUASHFS 173 default "3" 174 help 175 By default SquashFS caches the last 3 fragments read from 176 the filesystem. Increasing this amount may mean SquashFS 177 has to re-read fragments less often from disk, at the expense 178 of extra system memory. Decreasing this amount will mean 179 SquashFS uses less memory at the expense of extra reads from disk. 180 181 Note there must be at least one cached fragment. Anything 182 much more than three will probably not make much difference. 183