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xz: Update the man page about threading.

This commit is contained in:
Lasse Collin 2011-04-12 11:08:55 +03:00
parent 24e0406c0f
commit 70e750f597
1 changed files with 20 additions and 14 deletions
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src/xz/xz.1
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@ -5,7 +5,7 @@
.\" This file has been put into the public domain.
.\" You can do whatever you want with this file.
.\"
.TH XZ 1 "2011-04-11" "Tukaani" "XZ Utils"
.TH XZ 1 "2011-04-12" "Tukaani" "XZ Utils"
.
.SH NAME
xz, unxz, xzcat, lzma, unlzma, lzcat \- Compress or decompress .xz and .lzma files
@ -907,24 +907,30 @@ Automatic adjusting is always disabled when creating raw streams
.TP
\fB\-T\fR \fIthreads\fR, \fB\-\-threads=\fIthreads
Specify the number of worker threads to use.
Setting
.I threads
to a special value
.B 0
makes
.B xz
use as many threads as there are CPU cores on the system.
The actual number of threads can be less than
.I threads
if the input file is not big enough
for threading with the given settings or
if using more threads would exceed the memory usage limit.
.IP ""
.B "Multithreaded compression and decompression are not"
.B "implemented yet, so this option has no effect for now."
Currently the only threading method is to split the input into
blocks and compress them independently from each other.
The default block size depends on the compression level and
can be overriden with the
.BI \-\-block\-size= size
option.
.IP ""
.B "As of writing (2010-09-27), it hasn't been decided"
.B "if threads will be used by default on multicore systems"
.B "once support for threading has been implemented."
.B "Comments are welcome."
The complicating factor is that using many threads
will increase the memory usage dramatically.
Note that if multithreading will be the default,
it will probably be done so that single-threaded and
multithreaded modes produce the same output,
so compression ratio won't be significantly affected
if threading will be enabled by default.
.B "It is possible that the details of this option change before"
.B "the next stable XZ Utils release."
.B "This may include the meaning of the special value 0."
.\" FIXME
.
.SS "Custom compressor filter chains"
A custom filter chain allows specifying