kernel: Only build metal specific drivers for metal variants #2279
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Adjust kernel spec files to only merge `config-bottlerocket-metal` config fragment when the variant contains the substring `metal`. To make this work we need to force a rebuild of the kernel for each variant by setting the `variant-sensitive` option. Signed-off-by: Leonard Foerster <foersleo@amazon.com>
arnaldo2792
approved these changes
Jul 15, 2022
bcressey
approved these changes
Jul 16, 2022
I'd guess that this is because a full kernel build only takes 30 to 40 seconds longer than the full That's consistent with what I see on my ccache branch, which is that the kernel build speeds up by roughly 60 seconds, and finishes slightly before the |
markusboehme
approved these changes
Jul 18, 2022
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Issue number: #2211
Description of changes:
Make the kernels we use in metal variants (kernel-5.10 and kernel-5.15) variant-sensitive to force rebuild with every variant switch even if no changes happened to the code. Merge the metal specific config fragment conditionally on if we are building a metal kernel or not.
This is not an ideal solution as it will rebuild the kernel when there is no rebuild necessary, for example when switching from
aws-k8s-1.21toaws-k8s-1.22which use the same kernel. In practice the overhead from rebuilding the kernel for each variant is smaller than I anticipated (See testing below).Testing done:
In order to examine the impact of rebuilding the kernel for each variant switch I build a bunch of variants once with the patch and once without using the following script:
Grepping for interesting lines we can see the build time per variant and if a kernel was build.
without patch:
with patch:
We see roughly a 30 to 40 second increase in the build times with the rebuild per variant. I would have expected more impact here, but probably there is things about buildsys and some caching effects I do not fully understand yet.
With regards to the configurations we see the changes we would expect. For the metal variant there is no difference between building with or without this patch:
For non-metal variants we can see the expected difference in the configs:
aws-k8s-1.22for kernel-5.10: *aws-k8s-1.22for kernel-5.10: *Note: that the above config diffs do not include the config settings merged in #2271 as the experiments were done before rebasing on top of latest
developTerms of contribution:
By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.