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 28config SQUASHFS_XATTR 29 bool "Squashfs XATTR support" 30 depends on SQUASHFS 31 help 32 Saying Y here includes support for extended attributes (xattrs). 33 Xattrs are name:value pairs associated with inodes by 34 the kernel or by users (see the attr(5) manual page). 35 36 If unsure, say N. 37 38config SQUASHFS_ZLIB 39 bool "Include support for ZLIB compressed file systems" 40 depends on SQUASHFS 41 select ZLIB_INFLATE 42 default y 43 help 44 ZLIB compression is the standard compression used by Squashfs 45 file systems. It offers a good trade-off between compression 46 achieved and the amount of CPU time and memory necessary to 47 compress and decompress. 48 49 If unsure, say Y. 50 51config SQUASHFS_LZO 52 bool "Include support for LZO compressed file systems" 53 depends on SQUASHFS 54 select LZO_DECOMPRESS 55 help 56 Saying Y here includes support for reading Squashfs file systems 57 compressed with LZO compression. LZO compression is mainly 58 aimed at embedded systems with slower CPUs where the overheads 59 of zlib are too high. 60 61 LZO is not the standard compression used in Squashfs and so most 62 file systems will be readable without selecting this option. 63 64 If unsure, say N. 65 66config SQUASHFS_MULTI_DECOMPRESSOR 67 bool "Use multiple decompressors for handling parallel I/O" 68 depends on SQUASHFS 69 help 70 By default Squashfs uses a single decompressor but it gives 71 poor performance on parallel I/O workloads when using multiple CPU 72 machines due to waiting on decompressor availability. 73 74 If you have a parallel I/O workload and your system has enough memory, 75 using this option may improve overall I/O performance. 76 77 If unsure, say N. 78 79config SQUASHFS_XZ 80 bool "Include support for XZ compressed file systems" 81 depends on SQUASHFS 82 select XZ_DEC 83 help 84 Saying Y here includes support for reading Squashfs file systems 85 compressed with XZ compression. XZ gives better compression than 86 the default zlib compression, at the expense of greater CPU and 87 memory overhead. 88 89 XZ is not the standard compression used in Squashfs and so most 90 file systems will be readable without selecting this option. 91 92 If unsure, say N. 93 94config SQUASHFS_4K_DEVBLK_SIZE 95 bool "Use 4K device block size?" 96 depends on SQUASHFS 97 help 98 By default Squashfs sets the dev block size (sb_min_blocksize) 99 to 1K or the smallest block size supported by the block device 100 (if larger). This, because blocks are packed together and 101 unaligned in Squashfs, should reduce latency. 102 103 This, however, gives poor performance on MTD NAND devices where 104 the optimal I/O size is 4K (even though the devices can support 105 smaller block sizes). 106 107 Using a 4K device block size may also improve overall I/O 108 performance for some file access patterns (e.g. sequential 109 accesses of files in filesystem order) on all media. 110 111 Setting this option will force Squashfs to use a 4K device block 112 size by default. 113 114 If unsure, say N. 115 116config SQUASHFS_EMBEDDED 117 bool "Additional option for memory-constrained systems" 118 depends on SQUASHFS 119 help 120 Saying Y here allows you to specify cache size. 121 122 If unsure, say N. 123 124config SQUASHFS_FRAGMENT_CACHE_SIZE 125 int "Number of fragments cached" if SQUASHFS_EMBEDDED 126 depends on SQUASHFS 127 default "3" 128 help 129 By default SquashFS caches the last 3 fragments read from 130 the filesystem. Increasing this amount may mean SquashFS 131 has to re-read fragments less often from disk, at the expense 132 of extra system memory. Decreasing this amount will mean 133 SquashFS uses less memory at the expense of extra reads from disk. 134 135 Note there must be at least one cached fragment. Anything 136 much more than three will probably not make much difference. 137