SQUASHFS/squashfs-tools-4.4/RELEASE-READMEs/README-3.1

   1         SQUASHFS 3.1 - A squashed read-only filesystem for Linux
   2
   3         Copyright 2002-2006 Phillip Lougher <phillip@lougher.org.uk>
   4
   5         Released under the GPL licence (version 2 or later).
   6
   7 Welcome to Squashfs version 3.1-r2.  Squashfs 3.1 has major improvements to
   8 the Squashfs tools (Mksquashfs and Unsquashfs), some major bug fixes, new
   9 kernel patches, and various other smaller improvements and bug fixes.
  10 Please see the CHANGES file for a detailed list.
  11
  12 1. MKSQUASHFS
  13 -------------
  14
  15 Mksquashfs has been rewritten and it is now multi-threaded.  It offers
  16 the following improvements:
  17
  18 1. Parallel compression.  By default as many compression and fragment
  19 compression threads are created as there are available processors.
  20 This significantly speeds up performance on SMP systems.
  21
  22 2. File input and filesystem output is peformed in parallel on separate
  23 threads to maximise I/O performance.  Even on single processor systems
  24 this speeds up performance by at least 10%.
  25
  26 3. Appending has been significantly improved, and files within the
  27 filesystem being appended to are no longer scanned and checksummed.  This
  28 significantly improves append time for large filesystems.
  29
  30 4. File duplicate checking has been optimised, and split into two separate
  31 phases.  Only files which are considered possible duplicates after the
  32 first phase are checksummed and cached in memory.
  33
  34 5. The use of swap memory was found to significantly impact performance. The
  35 amount of memory used to cache the file is now a command line option, by default
  36 this is 512 Mbytes.
  37
  38 1.1 NEW COMMAND LINE OPTIONS
  39 ----------------------------
  40
  41 The new Mksquashfs program has a couple of extra command line options
  42 which can be used to control the new features:
  43
  44 -processors <processors>
  45
  46 This specifies the number of processors used by Mksquashfs.
  47 By default this is the number of available processors.
  48
  49 -read_queue <size in Mbytes>
  50
  51 This specifies the size of the file input queue used by the reader thread.
  52 This defaults to 64 Mbytes.
  53
  54 -write_queue <size in Mbytes>
  55
  56 This specifies the size of the filesystem output queue used by the
  57 writer thread.  It also specifies the maximum cache used in file
  58 duplicate detection (the output queue is shared between these tasks).
  59 This defaults to 512 Mbytes.
  60
  61 1.2 PERFORMANCE RESULTS
  62 -----------------------
  63
  64 The following results give an indication of the speed improvements.  Two
  65 example filesystems were tested, a liveCD filesystem (about 1.8 Gbytes
  66 uncompressed), and my home directory consisting largely of text files
  67 (about 1.3 Gbytes uncompressed).  Tests were run on a single core
  68 and a dual core system.
  69
  70 Dual Core (AMDx2 3800+) system:
  71 Source directories on ext3.
  72
  73 LiveCD, old mksquashfs:
  74
  75 real    11m48.401s
  76 user    9m27.056s
  77 sys     0m15.281s
  78
  79 LiveCD, new par_mksquashfs:
  80
  81 real    4m8.736s
  82 user    7m11.771s
  83 sys     0m27.749s
  84
  85 "Home", old mksquashfs:
  86
  87 real    4m34.360s
  88 user    3m54.007s
  89 sys     0m32.155s
  90
  91 "Home", new par_mksquashfs:
  92
  93 real    1m27.381s
  94 user    2m7.304s
  95 sys     0m17.234s
  96
  97 Single Core PowerBook (PowerPC G4 1.5 GHz Ubuntu Linux)
  98 Source directories on ext3.
  99
 100 LiveCD, old mksquashs:
 101
 102 real    11m38.472s
 103 user    9m6.137s
 104 sys     0m23.799s
 105
 106 LiveCD,  par_mksquashfs:
 107
 108 real    10m5.572s
 109 user    8m59.921s
 110 sys     0m16.145s
 111
 112 "Home", old mksquashfs:
 113
 114 real    3m42.298s
 115 user    2m49.478s
 116 sys     0m13.675s
 117
 118 "Home", new par_mksquashfs:
 119
 120 real    3m9.178s
 121 user    2m50.699s
 122 sys     0m9.069s
 123
 124 I'll be interested in any performance results obtained, especially from SMP
 125 machines larger than my dual-core AMD box, as this will give an indication of
 126 the scalability of the code.  Obviously, I'm also interested in any problems,
 127 deadlocks, low performance etc.
 128
 129 2. UNSQUASHFS
 130 -------------
 131
 132 Unsquashfs now allows you to specify the filename or directory that is to be
 133 extracted from the Squashfs filesystem, rather than always extracting the
 134 entire filesystem.  It also has a new "-force" option, and all options can be
 135 specified in a short form (-i rather than -info).
 136
 137 The Unsquashfs usage info is now:
 138
 139 SYNTAX: ./unsquashfs [options] filesystem [directory or file to extract]
 140         -v[ersion]              print version, licence and copyright information
 141         -i[nfo]                 print files as they are unsquashed
 142         -l[s]                   list filesystem only
 143         -d[est] <pathname>      unsquash to <pathname>, default "squashfs-root"
 144         -f[orce]                if file already exists then overwrite
 145
 146 To extract a subset of the filesystem, the filename or directory
 147 tree that is to be extracted can now be specified on the command line.  The
 148 file/directory should be specified using the full path to the file/directory
 149 as it appears within the Squashfs filesystem.  The file/directory will also be
 150 extracted to that position within the specified destination directory.
 151
 152 The new "-force" option forces Unsquashfs to output to the destination
 153 directory even if files or directories already exist.  This allows you
 154 to update an existing directory tree, or to Unsquashfs to a partially
 155 filled directory.  Without the "-force" option, Unsquashfs will
 156 refuse to overwrite any existing files, or to create any directories if they
 157 already exist.  This is done to protect data in case of mistakes, and
 158 so the "-force" option should be used with caution.