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-rw-r--r--src/xz/xz.134
1 files changed, 20 insertions, 14 deletions
diff --git a/src/xz/xz.1 b/src/xz/xz.1
index 8601aba5..ef89f406 100644
--- a/src/xz/xz.1
+++ b/src/xz/xz.1
@@ -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