On Fri, Nov 27, 2020 at 7:46 PM Sean Mooney <smooney@redhat.com> wrote:
On Fri, 2020-11-27 at 18:35 +0100, Arne Wiebalck wrote:
Hi,
I did a quick test (one data point):
- the image build time increased by 10 mins (on a VM, this is more than double compared to gzip) - but: the resulting image size is ~30% smaller (421 vs 297 MB) - the cleaning time (unpacking on bare metal!) increased by ~30 seconds
that is one of the main trade offs the lzma compression makes it front loads the computeational load to the comppression step requireing both more ram and time to do the initall compression while also achiviving a better compresison ratio while allowing light weight clients to decompress it without similar increase the time/ram requirement for the client. you may also want to consider the .xz format
Is it wildly supported for initramfs compression? I can, of course, try, but maybe you know. Dmitry
lzma and lzma2 have now been supperceed by .xz https://en.wikipedia.org/wiki/XZ_Utils
.xz format is becomming more an d more commen fro things liek compress kernel modules and packages.
So, lzma looks like a good option to reduce the image size which we had to do in our deployment already to address boot issues (we removed some packages).
Keeping gzip as the default and offering lzma as an option to start with as suggested by Sergii seems like a good way forward.
I also think it would be good to have someone else test as well to have another data point :-)
Cheers, Arne
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 <mailto: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,
On 27.11.20 14:00, Sergii Golovatiuk wrote: 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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-- SergiiGolovatiuk
Senior Software Developer
Red Hat <https://www.redhat.com/>
-- Red Hat GmbH, https://de.redhat.com/ , Registered seat: Grasbrunn, Commercial register: Amtsgericht Muenchen, HRB 153243, Managing Directors: Charles Cachera, Brian Klemm, Laurie Krebs, Michael O'Neill