Parallel compression not using all available CPU

PeerCorps Trust Fund ipc at peercorpstrust.org
Sat Dec 10 03:19:14 PST 2016


Hi,

I've observed that parallel compression tools such as pixz and lbzip2 do not make use of all of the available CPU under Dragonfly. On other OSes, it does.

When testing on a 50 gb file, using top I've observed that CPU idle percentages consistently hover around the 90% range for pixz and ~70% for lbzip2. These values under FreeBSD and Linux are typically ~0.0% idle until compression is complete. Correspondingly, compression takes significantly longer under Dragonfly, so the CPU is really being under utilized in this case as opposed to erroneous reporting by top.

This was tested on two systems, one 16c/32t and a 2c/2t system on a recent master DragonFly v4.7.0.973.g8d7da-DEVELOPMENT #2: Wed Dec  7 11:44:04 EET 2016.

Has anyone else possibly observed this?

-- 
Mike



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