Hi,

LZMA causes very high CPU and memory usage for creating images, leaving less resources for other processes. If Ironic is running alongside with other services that may cause significant impact for them. I would leave gzip option as default, would introduce --lzma as well as --gzip and use lzma on 5-10% of our CI resources to test how it goes. Then after a significant amount of testing we could turn it on as default. Proper deprecation should be applied here as well IMHO.

чт, 26 нояб. 2020 г. в 17:57, Dmitry Tantsur <dtantsur@redhat.com>:

Hi folks,

I've been playing with ways to reduce the size of our IPA images. While package removals can only save us tens of megabytes, switching from gzip to lzma reduces the size by around a third (from 373M to 217M in my testing).

What's the caveat? The unpacking time increases VERY substantially. On my nested virt lab the 217M image took around 5 minutes to unpack. I'm not sure how much it will impact real bare metal, please feel free to test https://review.opendev.org/c/openstack/ironic-python-agent-builder/+/764371 and tell me.

So, what do you think? Switching to lzma by default will likely affect CI run time (assuming we still have DIB jobs somewhere...) and development environments, but it will also provide a visible reduction in the image size (which benefit all environments). Large TripleO images may particularly benefit from this (but also particularly affected by the unpacking time).

Feedback is very welcome.

Dmitry

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