[ironic] [tripleo] RFC: lzma vs gzip for compressing IPA initramfs

Sergii Golovatiuk sgolovat at redhat.com
Fri Nov 27 13:00:10 UTC 2020


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 at 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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Sergii Golovatiuk

Senior Software Developer

Red Hat  <https://www.redhat.com/>
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