How do the different kernel editions vary?

Question

The official Ubuntu apt sources offer multiple editions of the kernel like generic, lowlatency, aws, azure, etc. E.g.:

$ apt-cache show linux-image-5\* | grep Package:
...
Package: linux-image-5.4.0-1036-gcp
Package: linux-image-5.4.0-1037-aws
Package: linux-image-5.4.0-1037-oracle
Package: linux-image-5.4.0-1039-azure
Package: linux-image-5.4.0-37-generic
Package: linux-image-5.4.0-37-lowlatency

How do these editions differ?

Is it merely a different configuration used during the compile of the kernel to tune specific parameters?
Are different kernel modules enabled/embedded by default?
Is the kernel source patched with different code?
Are they regularly rebased on a common mainline or did they diverge long ago and are now only mostly similar to each other?

How could I understand these differences myself?

Is there a public forum where the maintainers of these packages discuss why the gcp edition should vary from generic?
Is the source code, configuration and build process of each variant maintained publicly for comparison against a baseline?

I've struggled to find these answers myself but I likely haven't found the right place to look. From what I've seen so far, it appears we're just expected to run the azure variant of the kernel on Azure VMs , and run the aws variant on EC2, and not worry about why, or what the consequences might be of just using generic in all the cloud providers.

Update 1: Another StackExchange question does a decent job of explaining generic vs lowlatency but doesn't cover any of the cloud provider variants of the kernel.

Does this answer your question? Why choose a low latency kernel over a generic or real-time kernel? — guiverc, Feb 10 '21 at 03:25
With the low-latency kernel, it's generally advised to use the generic kernel unless you absolutely need to use low-latency, as some features of the OS won't work with low-latency (esp. kernel modules or drivers) — guiverc, Feb 10 '21 at 03:27
Does this answer your question? Where exactly is all the source code on Launchpad browseable? — muru, Feb 10 '21 at 04:26
For e.g., AWS, the sources are at https://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-aws/+git/xenial/tree/debian.aws — muru, Feb 10 '21 at 04:33
@muru how did you locate this source? I followed https://packages.ubuntu.com/bionic/linux-image-5.4.0-1037-aws to launchpad and only found an empty repo and one named usd-import-team which has various import commit messages and doesn't seem to be where the work actually happens. — Jason Stangroome, Feb 10 '21 at 05:22
I went to the source package (e.g., https://packages.ubuntu.com/source/bionic/linux-aws-5.4), scrolled to the bottom, where there's a command to clone the packaging source. I took the URL and swapped https for git. — muru, Feb 10 '21 at 08:58

How do the different kernel editions vary?

0 Answers0