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192.168.1.100 / T103 / 1f884588077ad3476b9c91cbb0ee9ee0332bbb68 / . / src / kernel / linux / v4.14 / fs / squashfs / Kconfig
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rjw1f884582022-01-06 17:20:42 +0800[diff] [blame^]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_ZSTD
141 bool "Include support for ZSTD compressed file systems"
142 depends on SQUASHFS
143 select ZSTD_DECOMPRESS
144 help
145 Saying Y here includes support for reading Squashfs file systems
146 compressed with ZSTD compression. ZSTD gives better compression than
147 the default ZLIB compression, while using less CPU.
148
149 ZSTD is not the standard compression used in Squashfs and so most
150 file systems will be readable without selecting this option.
151
152 If unsure, say N.
153
154config SQUASHFS_4K_DEVBLK_SIZE
155 bool "Use 4K device block size?"
156 depends on SQUASHFS
157 help
158 By default Squashfs sets the dev block size (sb_min_blocksize)
159 to 1K or the smallest block size supported by the block device
160 (if larger). This, because blocks are packed together and
161 unaligned in Squashfs, should reduce latency.
162
163 This, however, gives poor performance on MTD NAND devices where
164 the optimal I/O size is 4K (even though the devices can support
165 smaller block sizes).
166
167 Using a 4K device block size may also improve overall I/O
168 performance for some file access patterns (e.g. sequential
169 accesses of files in filesystem order) on all media.
170
171 Setting this option will force Squashfs to use a 4K device block
172 size by default.
173
174 If unsure, say N.
175
176config SQUASHFS_EMBEDDED
177 bool "Additional option for memory-constrained systems"
178 depends on SQUASHFS
179 help
180 Saying Y here allows you to specify cache size.
181
182 If unsure, say N.
183
184config SQUASHFS_FRAGMENT_CACHE_SIZE
185 int "Number of fragments cached" if SQUASHFS_EMBEDDED
186 depends on SQUASHFS
187 default "3"
188 help
189 By default SquashFS caches the last 3 fragments read from
190 the filesystem. Increasing this amount may mean SquashFS
191 has to re-read fragments less often from disk, at the expense
192 of extra system memory. Decreasing this amount will mean
193 SquashFS uses less memory at the expense of extra reads from disk.
194
195 Note there must be at least one cached fragment. Anything
196 much more than three will probably not make much difference.