Hello, I am using xz 5.2.1 (compiled from source) on Debian Jessie.
$ xz --version xz (XZ Utils) 5.2.1 liblzma 5.2.1 When I run parallel compress I see all cores utilized (checked with htop). xz -T 0 2275.dat However, when I attempt to run parallel decompress I only see a single core utilized. xz -d -T 0 2275.dat.xz The file I'm working with is sufficiently large (2.3G compressed ; 46G uncompressed) that I would expect significant benefit from decompression parallelism. I noticed that a few other users in the phoronix forum  were seeing similar behavior. Am I missing something obvious? Thanks, -Andy  http://www.phoronix.com/forums/forum/software/general-linux-open-source/47329-xz-5-2-adds-new-multi-threaded-options