Xz

xz^[1] compress or decompress (unxz) .xz and .lzma files but xz compresses by default to xz format.

xz support multi-threaded compression (-T flag)^[2] since 2014, version 5.2.0. ^[3], as of 2019 threaded decompression hasn’t been implemented yet. ^[4]. Number of threads can be less that defined is file is not big enough for threading with the given settings or if using more threads would exceed the memory usage limit. ^[5]

xz has replaced gzip in some uses case such as in Arch Linux packages because it decreases package size about 30% smaller depending on the data.

Options

--keep Once the target file has been successfully closed, the source file is removed unless --keep was specified

-T multi-threaded compression

Commands

xz --info-memory

xz --info-memory
Total amount of physical memory (RAM):  515,654 MiB (540,702,060,544 B)
Memory usage limit for compression:     Disabled
Memory usage limit for decompression:   Disabled

Use --verbose option twice to get extra information about compression, such us number of threads to use or memory required. It can impact xz performance.

xz -T0 --verbose --verbose file_to_compress

xz: Filter chain: --lzma2=dict=8MiB,lc=3,lp=0,pb=2,mode=normal,nice=64,mf=bt4,depth=0
xz: Using up to 48 threads.
xz: 7,925 MiB of memory is required. The limiter is disabled.
xz: Decompression will need 9 MiB of memory.
.../...

Examples

Test integrity:xz -tv linux-3.18.19.tar.xz
Compress data from stdin: echo "DATA TO COMPRESS" | xz --verbose > file.xz
Compress all files in directory and subdirectory except already compresed (.xz) using all CPUs (-T0):

find . -type f -not -name \*.xz -exec xz -T0 --verbose \{\} \;

xz file.txt

 xz: file.txt.xz: File exists

Activities

Compress your data using gzip and xz and compare sizes
Compare sizes of Linux Kernel source code depending of compression tools used: https://mirrors.edge.kernel.org/pub/linux/kernel/v5.x/
Compress your file using single thread xz and compress same file using all your available threads xz -T0
Compress your file with xz -T0 and verify that you are using all your threads with htop