diff options
Diffstat (limited to 'fs/squashfs/Kconfig')
| -rw-r--r-- | fs/squashfs/Kconfig | 130 |
1 files changed, 118 insertions, 12 deletions
diff --git a/fs/squashfs/Kconfig b/fs/squashfs/Kconfig index aa68a8a3151..b6fa8657dcb 100644 --- a/fs/squashfs/Kconfig +++ b/fs/squashfs/Kconfig @@ -1,16 +1,15 @@ config SQUASHFS tristate "SquashFS 4.0 - Squashed file system support" depends on BLOCK - select ZLIB_INFLATE help Saying Y here includes support for SquashFS 4.0 (a Compressed Read-Only File System). Squashfs is a highly compressed read-only - filesystem for Linux. It uses zlib/lzo compression to compress both - files, inodes and directories. Inodes in the system are very small - and all blocks are packed to minimise data overhead. Block sizes - greater than 4K are supported up to a maximum of 1 Mbytes (default - block size 128K). SquashFS 4.0 supports 64 bit filesystems and files - (larger than 4GB), full uid/gid information, hard links and + filesystem for Linux. It uses zlib, lzo or xz compression to + compress both files, inodes and directories. Inodes in the system + are very small and all blocks are packed to minimise data overhead. + Block sizes greater than 4K are supported up to a maximum of 1 Mbytes + (default block size 128K). SquashFS 4.0 supports 64 bit filesystems + and files (larger than 4GB), full uid/gid information, hard links and timestamps. Squashfs is intended for general read-only filesystem use, for @@ -20,12 +19,84 @@ config SQUASHFS If you want to compile this as a module ( = code which can be inserted in and removed from the running kernel whenever you want), - say M here and read <file:Documentation/modules.txt>. The module - will be called squashfs. Note that the root file system (the one - containing the directory /) cannot be compiled as a module. + say M here. The module will be called squashfs. Note that the root + file system (the one containing the directory /) cannot be compiled + as a module. If unsure, say N. +choice + prompt "File decompression options" + depends on SQUASHFS + help + Squashfs now supports two options for decompressing file + data. Traditionally Squashfs has decompressed into an + intermediate buffer and then memcopied it into the page cache. + Squashfs now supports the ability to decompress directly into + the page cache. + + If unsure, select "Decompress file data into an intermediate buffer" + +config SQUASHFS_FILE_CACHE + bool "Decompress file data into an intermediate buffer" + help + Decompress file data into an intermediate buffer and then + memcopy it into the page cache. + +config SQUASHFS_FILE_DIRECT + bool "Decompress files directly into the page cache" + help + Directly decompress file data into the page cache. + Doing so can significantly improve performance because + it eliminates a memcpy and it also removes the lock contention + on the single buffer. + +endchoice + +choice + prompt "Decompressor parallelisation options" + depends on SQUASHFS + help + Squashfs now supports three parallelisation options for + decompression. Each one exhibits various trade-offs between + decompression performance and CPU and memory usage. + + If in doubt, select "Single threaded compression" + +config SQUASHFS_DECOMP_SINGLE + bool "Single threaded compression" + help + Traditionally Squashfs has used single-threaded decompression. + Only one block (data or metadata) can be decompressed at any + one time. This limits CPU and memory usage to a minimum. + +config SQUASHFS_DECOMP_MULTI + bool "Use multiple decompressors for parallel I/O" + help + By default Squashfs uses a single decompressor but it gives + poor performance on parallel I/O workloads when using multiple CPU + machines due to waiting on decompressor availability. + + If you have a parallel I/O workload and your system has enough memory, + using this option may improve overall I/O performance. + + This decompressor implementation uses up to two parallel + decompressors per core. It dynamically allocates decompressors + on a demand basis. + +config SQUASHFS_DECOMP_MULTI_PERCPU + bool "Use percpu multiple decompressors for parallel I/O" + help + By default Squashfs uses a single decompressor but it gives + poor performance on parallel I/O workloads when using multiple CPU + machines due to waiting on decompressor availability. + + This decompressor implementation uses a maximum of one + decompressor per core. It uses percpu variables to ensure + decompression is load-balanced across the cores. + +endchoice + config SQUASHFS_XATTR bool "Squashfs XATTR support" depends on SQUASHFS @@ -36,13 +107,26 @@ config SQUASHFS_XATTR If unsure, say N. +config SQUASHFS_ZLIB + bool "Include support for ZLIB compressed file systems" + depends on SQUASHFS + select ZLIB_INFLATE + default y + help + ZLIB compression is the standard compression used by Squashfs + file systems. It offers a good trade-off between compression + achieved and the amount of CPU time and memory necessary to + compress and decompress. + + If unsure, say Y. + config SQUASHFS_LZO bool "Include support for LZO compressed file systems" depends on SQUASHFS select LZO_DECOMPRESS help Saying Y here includes support for reading Squashfs file systems - compressed with LZO compresssion. LZO compression is mainly + compressed with LZO compression. LZO compression is mainly aimed at embedded systems with slower CPUs where the overheads of zlib are too high. @@ -57,7 +141,7 @@ config SQUASHFS_XZ select XZ_DEC help Saying Y here includes support for reading Squashfs file systems - compressed with XZ compresssion. XZ gives better compression than + compressed with XZ compression. XZ gives better compression than the default zlib compression, at the expense of greater CPU and memory overhead. @@ -66,6 +150,28 @@ config SQUASHFS_XZ If unsure, say N. +config SQUASHFS_4K_DEVBLK_SIZE + bool "Use 4K device block size?" + depends on SQUASHFS + help + By default Squashfs sets the dev block size (sb_min_blocksize) + to 1K or the smallest block size supported by the block device + (if larger). This, because blocks are packed together and + unaligned in Squashfs, should reduce latency. + + This, however, gives poor performance on MTD NAND devices where + the optimal I/O size is 4K (even though the devices can support + smaller block sizes). + + Using a 4K device block size may also improve overall I/O + performance for some file access patterns (e.g. sequential + accesses of files in filesystem order) on all media. + + Setting this option will force Squashfs to use a 4K device block + size by default. + + If unsure, say N. + config SQUASHFS_EMBEDDED bool "Additional option for memory-constrained systems" depends on SQUASHFS |