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In a Ubuntu instance in GCE, I have 614 unpigz child processes under dockerd when examining the processes via ps afx. Normal? After restarting Docker, is there a chance that it gets reproduced...?

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    What are you running in docker? Apr 11 '19 at 18:01
  • Couple of node processes in a phusion baseimage based image. In the host side there is an automation that keeps sure that the latest image from the registry is being used. I don’t think it is related to the image internals since the container has been upgraded recently and that didn’t affect the situation. Apr 11 '19 at 18:08
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This is a BUG actually (see https://github.com/moby/moby/issues/38608). These processes will disappear after Docker service restart, but they will be created again as long as you use Docker's ADD *.tar.gz (or similar) feature.

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Inefficient but not dangerous. You make the decision of whether lots of processes like this is healthy for your environment.

pigz is a parallel implementation of gzip. The default maximum for --processes is the number of online processors, and each container sees all the CPUs of the system. They will compete for CPU and I/O, so may pile up and thrash the Linux scheduler a bit.

Optimum number of process is probably closer to 2x the number of CPUs. If you run lots of pigz at once, it may be more effecient to serialize those, reduce --processes, or use regular not-threaded gunzip.

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