Re: Building (Debian) kernel optimized for RPi Zero (W) and 1
On Tue, Oct 25, 2022, at 11:15, Diederik de Haas wrote:
> On Tuesday, 25 October 2022 10:02:09 CEST Andrew M.A. Cater wrote:
>> Debian armel runs fine without recompilation at a slight penalty.
>
> It is exactly this 'slight penalty' that I want to verify.
>
> I have a Zero W running Debian's armel kernel and I find that device to be
> annoyingly slow.
> I also have a RPi 1 running raspbian.org's 4.9 kernel, which is a special
> kernel build by plugwash and compiled like the rest of raspbian.org packages,
> which I do not find (annoyingly) slow.
The difference between the two kernels is almost certainly unrelated
to the toolchain they are built with, and entirely based on the
kernel patches that are added on top of mainline as well as the
configuration.
If there is a huge difference, my first guess would be the CPU frequency
scaling driver: if the CPU runs a different operating point, that
would have a much larger impact than anything the kernel itself
can do. Another obvious difference may be the GPU support: if you
the HDMI output, having an accelerated driver for it will feel
much faster than running on a plain framebuffer.
If you have a fast Raspbian kernel and a slow Debian kernel for
the same source version, can you take a look at the /boot/config-*
files, and the list of loaded kernel modules, to see if there
are any obvious differences?
Arnd
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