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Reinstitute 2GB window limit on 32 bit. It still doesn't work. However we can now decompress larger windows.

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Do more mmap in place of malloc.
Update docs.
Remove redundant code.
This commit is contained in:
Con Kolivas 2010-11-01 22:55:59 +11:00
parent 0e09c9ec24
commit 772fbf602e
4 changed files with 25 additions and 24 deletions
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22
README
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@ -1,4 +1,4 @@
lrzip v0.47
lrzip v0.50
Long Range ZIP or Lzma RZIP
@ -62,8 +62,9 @@ lrztar wrapper to fake a complete archiver.
2. It requires a lot of memory to get the best performance out of, and is not
really usable (for compression) with less than 256MB. Decompression requires
less ram and works on smaller ram machines.
3. It works on stdin/out but in a very inefficent manner generating temporary
files on disk so this method of using lrzip is not recommended.
3. stdin on decompression and stdout on compression work but in a very
inefficient manner generating temporary files on disk so this method of using
lrzip is not recommended (the other combinations of stdin/out work nicely).
See the file README.benchmarks in doc/ for performance examples and what kind
of data lrzip is very good with.
@ -105,7 +106,7 @@ Q. 32bit?
A. 32bit machines have a limit of 2GB sized compression windows due to
userspace limitations on mmap and malloc, so even if you have much more ram
you will not be able to use compression windows larger than 2GB. Also you
will be unable to decompress files compressed on 64bit machines which have
may be unable to decompress files compressed on 64bit machines which have
used windows larger than 2GB.
Q. How about 64bit?
@ -117,8 +118,11 @@ Q. Other operating systems?
A. Patches are welcome. Version 0.43+ should build on MacOSX 10.5+
Q. Does it work on stdin/stdout?
A. Yes, but the performance of this mode is low because it basically copies
the data to temporary files. Not recommended!
A. Yes it does. The two most common uses, compression from stdin and
decompression to stdout work nicely. However the other combinations of
decompression from stdin and compression to stdout use temporary files on
disk because of seeking requirements so the performance of these mode is low.
Not recommended!
Q. I have another compression format that is even better than zpaq, can you
use that?
@ -154,7 +158,7 @@ generated file be decompressed on machines with less ram?
A. Yes. Ram requirements for decompression go up only by the -L compression
option with lzma and are never anywhere near as large as the compression
requirements. However if you're on 64bit and you use a compression window
greater than 2GB, it will NOT be possible to decompress it on 32bit machines.
greater than 2GB, it may NOT be possible to decompress it on 32bit machines.
lrzip will warn you and fail if you try.
Q. I've changed the compression level with -L in combination with -l or -z and
@ -301,7 +305,7 @@ A. See http://www.7-zip.org and http://www.p7zip.org. Also, see the file
LIMITATIONS
Due to mmap limitations the maximum size a window can be set to is currently
2GB on 32bit. Files generated on 64 bit machines with windows >2GB in size
will not be decompressible on 32bit machines.
may not be decompressible on 32bit machines.
BUGS:
Probably lots.
@ -329,7 +333,7 @@ Ed Avis for various fixes. Thanks to Matt Mahoney for zpaq code. Thanks to
Jukka Laurila for Darwin support. Thanks to George Makrydakis for lrztar.
Con Kolivas <kernel@kolivas.org>
Sat, 22 May 2010
Mon, 1 Nov 2010
Also documented by
Peter Hyman <pete@peterhyman.com>