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xz: Fix outdated threading related info on the man page.

This commit is contained in:
Lasse Collin 2024-02-13 11:38:10 +02:00
parent 3182a330c1
commit 0709c2b2d7
1 changed files with 14 additions and 8 deletions
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@ -4,7 +4,7 @@
.\" Authors: Lasse Collin
.\" Jia Tan
.\"
.TH XZ 1 "2024-01-23" "Tukaani" "XZ Utils"
.TH XZ 1 "2024-02-13" "Tukaani" "XZ Utils"
.
.SH NAME
xz, unxz, xzcat, lzma, unlzma, lzcat \- Compress or decompress .xz and .lzma files
@ -799,8 +799,6 @@ in the single-threaded mode.
It may vary slightly between
.B xz
versions.
Memory requirements of some of the future multithreaded modes may
be dramatically higher than that of the single-threaded mode.
.IP \(bu 3
DecMem contains the decompressor memory requirements.
That is, the compression settings determine
@ -809,6 +807,15 @@ The exact decompressor memory usage is slightly more than
the LZMA2 dictionary size, but the values in the table
have been rounded up to the next full MiB.
.RE
.IP ""
Memory requirements of the multi-threaded mode are
significantly higher than that of the single-threaded mode.
With the default value of
.BR \-\-block\-size ,
each thread needs 3*3*DictSize plus CompMem or DecMem.
For example, four threads with preset
.B \-6
needs 660\(en670\ MiB of memory.
.TP
.BR \-e ", " \-\-extreme
Use a slower variant of the selected compression preset level
@ -900,17 +907,16 @@ Using
.I size
less than the LZMA2 dictionary size is waste of RAM
because then the LZMA2 dictionary buffer will never get fully used.
The sizes of the blocks are stored in the block headers,
which a future version of
.B xz
will use for multi-threaded decompression.
In multi-threaded mode,
the sizes of the blocks are stored in the block headers.
This size information is required for multi-threaded decompression.
.IP ""
In single-threaded mode no block splitting is done by default.
Setting this option doesn't affect memory usage.
No size information is stored in block headers,
thus files created in single-threaded mode
won't be identical to files created in multi-threaded mode.
The lack of size information also means that a future version of
The lack of size information also means that
.B xz
won't be able decompress the files in multi-threaded mode.
.TP