NACK: [U/N][PATCH 0/2] Provide python perf module

[Kevin Becker]

On Fri, Mar 22, 2024 at 11:47 AM Andrea Righi
<andrea.righi at canonical.com> wrote:
>
> [Impact]
>
> We need to provide the python perf module, because some applications
> (such as tuned) require it.
>
> This module is implemented inside perf, provided by the kernel.
>
> At the moment we provide a distinct perf for each kernel installed in
> the system. There is really no reason to do that, because perf is both
> backward and forward compatible, but this is a different issue and we
> are not going to solve it in this context and it will be addressed in a
> separate bug.
>
> For now, to solve this specific issue, we need to enable the python
> module when we build perf (as part of the kernel build) and ship the
> library inside the linux-tools-<kernel_abi_version> package.
>
> However, this brings a new problem, because we need to install the
> module in a standard python path (so that python applications can be
> able to use it in a regular way), but we need to support multiple
> installed versions and add some logic to transparently select the right
> one when a generic user-space python application uses `import perf`.
>
> For this reason we need to provide a python wrapper module that is
> imported via a regular `import perf` and it transparently loads the
> actual python perf module, based on the kernel that is currently
> running.
>
> [Test case]
>
> Install linux-tools-<kernel_version> and run the following simple test
> case:
>
>  $ python3 -c 'import perf; [print(c) for c in perf.cpu_map()]'
>
> [Fix]
>
>  - Enable the python perf module build during the regular kernel build
>  - Provide a virtual `perf` python module wrapper in linux-tools-common
>
> [Regression potential]
>
> We are adding a new python module to linux-tools (that is something new,
> we don't ship any other python module), but we are not changing anything
> that is already provided, so the only regression that can happen is an
> increased size of the linux-tools package.

The perf module loader in patch 2 looks good, but there's a typo in
patch 1. In debian.master/rules.d/s390x.mk, it has "to_tools" on two
lines as opposed to "do_tools" like the rest.

-Kevin