| SQUASHFS 3.1 - A squashed read-only filesystem for Linux |
| |
| Copyright 2002-2006 Phillip Lougher <phillip@lougher.org.uk> |
| |
| Released under the GPL licence (version 2 or later). |
| |
| Welcome to Squashfs version 3.1-r2. Squashfs 3.1 has major improvements to |
| the Squashfs tools (Mksquashfs and Unsquashfs), some major bug fixes, new |
| kernel patches, and various other smaller improvements and bug fixes. |
| Please see the CHANGES file for a detailed list. |
| |
| 1. MKSQUASHFS |
| ------------- |
| |
| Mksquashfs has been rewritten and it is now multi-threaded. It offers |
| the following improvements: |
| |
| 1. Parallel compression. By default as many compression and fragment |
| compression threads are created as there are available processors. |
| This significantly speeds up performance on SMP systems. |
| |
| 2. File input and filesystem output is peformed in parallel on separate |
| threads to maximise I/O performance. Even on single processor systems |
| this speeds up performance by at least 10%. |
| |
| 3. Appending has been significantly improved, and files within the |
| filesystem being appended to are no longer scanned and checksummed. This |
| significantly improves append time for large filesystems. |
| |
| 4. File duplicate checking has been optimised, and split into two separate |
| phases. Only files which are considered possible duplicates after the |
| first phase are checksummed and cached in memory. |
| |
| 5. The use of swap memory was found to significantly impact performance. The |
| amount of memory used to cache the file is now a command line option, by default |
| this is 512 Mbytes. |
| |
| 1.1 NEW COMMAND LINE OPTIONS |
| ---------------------------- |
| |
| The new Mksquashfs program has a couple of extra command line options |
| which can be used to control the new features: |
| |
| -processors <processors> |
| |
| This specifies the number of processors used by Mksquashfs. |
| By default this is the number of available processors. |
| |
| -read_queue <size in Mbytes> |
| |
| This specifies the size of the file input queue used by the reader thread. |
| This defaults to 64 Mbytes. |
| |
| -write_queue <size in Mbytes> |
| |
| This specifies the size of the filesystem output queue used by the |
| writer thread. It also specifies the maximum cache used in file |
| duplicate detection (the output queue is shared between these tasks). |
| This defaults to 512 Mbytes. |
| |
| 1.2 PERFORMANCE RESULTS |
| ----------------------- |
| |
| The following results give an indication of the speed improvements. Two |
| example filesystems were tested, a liveCD filesystem (about 1.8 Gbytes |
| uncompressed), and my home directory consisting largely of text files |
| (about 1.3 Gbytes uncompressed). Tests were run on a single core |
| and a dual core system. |
| |
| Dual Core (AMDx2 3800+) system: |
| Source directories on ext3. |
| |
| LiveCD, old mksquashfs: |
| |
| real 11m48.401s |
| user 9m27.056s |
| sys 0m15.281s |
| |
| LiveCD, new par_mksquashfs: |
| |
| real 4m8.736s |
| user 7m11.771s |
| sys 0m27.749s |
| |
| "Home", old mksquashfs: |
| |
| real 4m34.360s |
| user 3m54.007s |
| sys 0m32.155s |
| |
| "Home", new par_mksquashfs: |
| |
| real 1m27.381s |
| user 2m7.304s |
| sys 0m17.234s |
| |
| Single Core PowerBook (PowerPC G4 1.5 GHz Ubuntu Linux) |
| Source directories on ext3. |
| |
| LiveCD, old mksquashs: |
| |
| real 11m38.472s |
| user 9m6.137s |
| sys 0m23.799s |
| |
| LiveCD, par_mksquashfs: |
| |
| real 10m5.572s |
| user 8m59.921s |
| sys 0m16.145s |
| |
| "Home", old mksquashfs: |
| |
| real 3m42.298s |
| user 2m49.478s |
| sys 0m13.675s |
| |
| "Home", new par_mksquashfs: |
| |
| real 3m9.178s |
| user 2m50.699s |
| sys 0m9.069s |
| |
| I'll be interested in any performance results obtained, especially from SMP |
| machines larger than my dual-core AMD box, as this will give an indication of |
| the scalability of the code. Obviously, I'm also interested in any problems, |
| deadlocks, low performance etc. |
| |
| 2. UNSQUASHFS |
| ------------- |
| |
| Unsquashfs now allows you to specify the filename or directory that is to be |
| extracted from the Squashfs filesystem, rather than always extracting the |
| entire filesystem. It also has a new "-force" option, and all options can be |
| specified in a short form (-i rather than -info). |
| |
| The Unsquashfs usage info is now: |
| |
| SYNTAX: ./unsquashfs [options] filesystem [directory or file to extract] |
| -v[ersion] print version, licence and copyright information |
| -i[nfo] print files as they are unsquashed |
| -l[s] list filesystem only |
| -d[est] <pathname> unsquash to <pathname>, default "squashfs-root" |
| -f[orce] if file already exists then overwrite |
| |
| To extract a subset of the filesystem, the filename or directory |
| tree that is to be extracted can now be specified on the command line. The |
| file/directory should be specified using the full path to the file/directory |
| as it appears within the Squashfs filesystem. The file/directory will also be |
| extracted to that position within the specified destination directory. |
| |
| The new "-force" option forces Unsquashfs to output to the destination |
| directory even if files or directories already exist. This allows you |
| to update an existing directory tree, or to Unsquashfs to a partially |
| filled directory. Without the "-force" option, Unsquashfs will |
| refuse to overwrite any existing files, or to create any directories if they |
| already exist. This is done to protect data in case of mistakes, and |
| so the "-force" option should be used with caution. |
