2 tristate "SquashFS 4.0 - Squashed file system support"
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
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.
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
29 bool "Squashfs XATTR support"
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).
39 bool "Include support for ZLIB compressed file systems"
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.
52 bool "Include support for LZO compressed file systems"
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
61 LZO is not the standard compression used in Squashfs and so most
62 file systems will be readable without selecting this option.
66 config SQUASHFS_MULTI_DECOMPRESSOR
67 bool "Use multiple decompressors for handling parallel I/O"
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.
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.
80 bool "Include support for XZ compressed file systems"
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
89 XZ is not the standard compression used in Squashfs and so most
90 file systems will be readable without selecting this option.
94 config SQUASHFS_4K_DEVBLK_SIZE
95 bool "Use 4K device block size?"
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.
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).
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.
111 Setting this option will force Squashfs to use a 4K device block
116 config SQUASHFS_EMBEDDED
117 bool "Additional option for memory-constrained systems"
120 Saying Y here allows you to specify cache size.
124 config SQUASHFS_FRAGMENT_CACHE_SIZE
125 int "Number of fragments cached" if SQUASHFS_EMBEDDED
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.
135 Note there must be at least one cached fragment. Anything
136 much more than three will probably not make much difference.