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Alexey Dobriyan22635ec2009-01-22 10:57:46 +03001config SQUASHFS
2 tristate "SquashFS 4.0 - Squashed file system support"
3 depends on BLOCK
Alexey Dobriyan22635ec2009-01-22 10:57:46 +03004 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
Phillip Lougher681ffe22011-02-28 16:21:34 +00007 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
Phillip Lougher4b676d22010-08-05 23:42:54 +010013 timestamps.
Alexey Dobriyan22635ec2009-01-22 10:57:46 +030014
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),
Paul Bolle395cf962011-08-15 02:02:26 +020022 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.
Alexey Dobriyan22635ec2009-01-22 10:57:46 +030025
26 If unsure, say N.
27
Phillip Lougherd2083832013-11-18 02:31:36 +000028choice
Phillip Lougher0d455c12013-11-13 02:04:19 +000029 prompt "File decompression options"
30 depends on SQUASHFS
31 help
32 Squashfs now supports two options for decompressing file
33 data. Traditionally Squashfs has decompressed into an
34 intermediate buffer and then memcopied it into the page cache.
35 Squashfs now supports the ability to decompress directly into
36 the page cache.
37
38 If unsure, select "Decompress file data into an intermediate buffer"
39
40config SQUASHFS_FILE_CACHE
41 bool "Decompress file data into an intermediate buffer"
42 help
43 Decompress file data into an intermediate buffer and then
44 memcopy it into the page cache.
45
46config SQUASHFS_FILE_DIRECT
47 bool "Decompress files directly into the page cache"
48 help
49 Directly decompress file data into the page cache.
50 Doing so can significantly improve performance because
51 it eliminates a memcpy and it also removes the lock contention
52 on the single buffer.
53
54endchoice
55
56choice
Phillip Lougherd2083832013-11-18 02:31:36 +000057 prompt "Decompressor parallelisation options"
58 depends on SQUASHFS
59 help
60 Squashfs now supports three parallelisation options for
61 decompression. Each one exhibits various trade-offs between
62 decompression performance and CPU and memory usage.
63
64 If in doubt, select "Single threaded compression"
65
66config SQUASHFS_DECOMP_SINGLE
67 bool "Single threaded compression"
68 help
69 Traditionally Squashfs has used single-threaded decompression.
70 Only one block (data or metadata) can be decompressed at any
71 one time. This limits CPU and memory usage to a minimum.
72
73config SQUASHFS_DECOMP_MULTI
74 bool "Use multiple decompressors for parallel I/O"
75 help
76 By default Squashfs uses a single decompressor but it gives
77 poor performance on parallel I/O workloads when using multiple CPU
78 machines due to waiting on decompressor availability.
79
80 If you have a parallel I/O workload and your system has enough memory,
81 using this option may improve overall I/O performance.
82
83 This decompressor implementation uses up to two parallel
84 decompressors per core. It dynamically allocates decompressors
85 on a demand basis.
86
87config SQUASHFS_DECOMP_MULTI_PERCPU
88 bool "Use percpu multiple decompressors for parallel I/O"
89 help
90 By default Squashfs uses a single decompressor but it gives
91 poor performance on parallel I/O workloads when using multiple CPU
92 machines due to waiting on decompressor availability.
93
94 This decompressor implementation uses a maximum of one
95 decompressor per core. It uses percpu variables to ensure
96 decompression is load-balanced across the cores.
97
98endchoice
99
Phillip Lougher637d5c92010-05-31 18:46:29 +0100100config SQUASHFS_XATTR
Phillip Lougher01e5b4e2010-05-17 19:39:02 +0100101 bool "Squashfs XATTR support"
102 depends on SQUASHFS
Phillip Lougher01e5b4e2010-05-17 19:39:02 +0100103 help
104 Saying Y here includes support for extended attributes (xattrs).
105 Xattrs are name:value pairs associated with inodes by
106 the kernel or by users (see the attr(5) manual page).
107
108 If unsure, say N.
109
Phillip Loughercc6d3492011-07-22 03:01:28 +0100110config SQUASHFS_ZLIB
111 bool "Include support for ZLIB compressed file systems"
112 depends on SQUASHFS
113 select ZLIB_INFLATE
114 default y
115 help
116 ZLIB compression is the standard compression used by Squashfs
117 file systems. It offers a good trade-off between compression
118 achieved and the amount of CPU time and memory necessary to
119 compress and decompress.
120
121 If unsure, say Y.
122
Chan Jeong79cb8ce2010-08-05 02:29:59 +0100123config SQUASHFS_LZO
124 bool "Include support for LZO compressed file systems"
125 depends on SQUASHFS
126 select LZO_DECOMPRESS
Phillip Lougher4b676d22010-08-05 23:42:54 +0100127 help
128 Saying Y here includes support for reading Squashfs file systems
Justin P. Mattock70f23fd2011-05-10 10:16:21 +0200129 compressed with LZO compression. LZO compression is mainly
Phillip Lougher4b676d22010-08-05 23:42:54 +0100130 aimed at embedded systems with slower CPUs where the overheads
131 of zlib are too high.
132
133 LZO is not the standard compression used in Squashfs and so most
134 file systems will be readable without selecting this option.
135
136 If unsure, say N.
Chan Jeong79cb8ce2010-08-05 02:29:59 +0100137
Phillip Lougher7a43ae52010-12-09 02:08:31 +0000138config SQUASHFS_XZ
139 bool "Include support for XZ compressed file systems"
140 depends on SQUASHFS
141 select XZ_DEC
142 help
143 Saying Y here includes support for reading Squashfs file systems
Justin P. Mattock70f23fd2011-05-10 10:16:21 +0200144 compressed with XZ compression. XZ gives better compression than
Phillip Lougher7a43ae52010-12-09 02:08:31 +0000145 the default zlib compression, at the expense of greater CPU and
146 memory overhead.
147
148 XZ is not the standard compression used in Squashfs and so most
149 file systems will be readable without selecting this option.
150
151 If unsure, say N.
152
Phillip Lougher7657cac2011-10-22 01:34:48 +0100153config SQUASHFS_4K_DEVBLK_SIZE
154 bool "Use 4K device block size?"
155 depends on SQUASHFS
156 help
157 By default Squashfs sets the dev block size (sb_min_blocksize)
158 to 1K or the smallest block size supported by the block device
159 (if larger). This, because blocks are packed together and
160 unaligned in Squashfs, should reduce latency.
161
162 This, however, gives poor performance on MTD NAND devices where
163 the optimal I/O size is 4K (even though the devices can support
164 smaller block sizes).
165
166 Using a 4K device block size may also improve overall I/O
167 performance for some file access patterns (e.g. sequential
168 accesses of files in filesystem order) on all media.
169
170 Setting this option will force Squashfs to use a 4K device block
171 size by default.
172
173 If unsure, say N.
174
Alexey Dobriyan22635ec2009-01-22 10:57:46 +0300175config SQUASHFS_EMBEDDED
Phillip Lougher4b676d22010-08-05 23:42:54 +0100176 bool "Additional option for memory-constrained systems"
Alexey Dobriyan22635ec2009-01-22 10:57:46 +0300177 depends on SQUASHFS
Alexey Dobriyan22635ec2009-01-22 10:57:46 +0300178 help
179 Saying Y here allows you to specify cache size.
180
181 If unsure, say N.
182
183config SQUASHFS_FRAGMENT_CACHE_SIZE
184 int "Number of fragments cached" if SQUASHFS_EMBEDDED
185 depends on SQUASHFS
186 default "3"
187 help
188 By default SquashFS caches the last 3 fragments read from
189 the filesystem. Increasing this amount may mean SquashFS
190 has to re-read fragments less often from disk, at the expense
191 of extra system memory. Decreasing this amount will mean
192 SquashFS uses less memory at the expense of extra reads from disk.
193
194 Note there must be at least one cached fragment. Anything
195 much more than three will probably not make much difference.