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22635ec9 AD |
1 | config SQUASHFS |
2 | tristate "SquashFS 4.0 - Squashed file system support" | |
3 | depends on BLOCK | |
22635ec9 AD |
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 | |
681ffe2e PL |
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 | |
4b676d2d | 13 | timestamps. |
22635ec9 AD |
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), | |
395cf969 PB |
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. | |
22635ec9 AD |
25 | |
26 | If unsure, say N. | |
27 | ||
637d5c9a | 28 | config SQUASHFS_XATTR |
01e5b4e4 PL |
29 | bool "Squashfs XATTR support" |
30 | depends on SQUASHFS | |
01e5b4e4 PL |
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 | ||
cc6d3497 PL |
38 | config 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 | ||
79cb8ced CJ |
51 | config SQUASHFS_LZO |
52 | bool "Include support for LZO compressed file systems" | |
53 | depends on SQUASHFS | |
54 | select LZO_DECOMPRESS | |
4b676d2d PL |
55 | help |
56 | Saying Y here includes support for reading Squashfs file systems | |
70f23fd6 | 57 | compressed with LZO compression. LZO compression is mainly |
4b676d2d PL |
58 | aimed at embedded systems with slower CPUs where the overheads |
59 | of zlib are too high. | |
79cb8ced | 60 | |
4b676d2d PL |
61 | LZO is not the standard compression used in Squashfs and so most |
62 | file systems will be readable without selecting this option. | |
22635ec9 | 63 | |
4b676d2d | 64 | If unsure, say N. |
cd59c2ec MK |
65 | |
66 | config 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. | |
4b676d2d | 78 | |
7a43ae52 PL |
79 | config 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 | |
70f23fd6 | 85 | compressed with XZ compression. XZ gives better compression than |
7a43ae52 PL |
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 | ||
7657cacf PL |
94 | config 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 | ||
4b676d2d PL |
116 | config SQUASHFS_EMBEDDED |
117 | bool "Additional option for memory-constrained systems" | |
22635ec9 | 118 | depends on SQUASHFS |
22635ec9 AD |
119 | help |
120 | Saying Y here allows you to specify cache size. | |
121 | ||
122 | If unsure, say N. | |
123 | ||
124 | config 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. |