Re: More progress to report [Re: Debian Bullseye on Raspberry Pi 4 4GB?]

[LinAdmin <linadmin@quickline.ch>]

The common believe that on the same hardware 64-bit must be better or equal to 32-bit is clearly wrong for the "crazy" BCM2711 chip used in Pi4.

The detailed benchmarks for Raspian Buster are at 32 Bit Kernel 4.19 and 64 Bit Kernel 5.4. showing for calculation AES 16KB  50% less throughput for 64-bit.

On my system I get similar results e.g. for AES-128 (16KB):

    Salsa Buster arm64     5.9.0   42'000

    Ubuntu LTS armv7l      5.4      92'000

When playing a FullHD video coded H265, the average CPU load is 80% on 64-bit and less than 30% on 32-bit!

Similar situations when encoding to H265 using ffmpeg .

LinAdmin

On 02.03.21 21:30, Arnd Bergmann wrote:

> On Tue, Mar 2, 2021 at 7:51 PM LinAdmin <linadmin@quickline.ch> wrote:
>
> > > There is really no good reason to run a 32-bit /kernel/ on the Pi 4,
> > > especially the version
> > > with 8GB RAM. While the bug should get fixed in principle to make the
> > > default kernel
> > > work and allow installing a 32-bit distro, the best setup for this
> > > machine (especially
> > > the versions with less than 4GB) is to use an armhf user space with a
> > > 64-bit kernel.
> > >         
> > Benchmarking shows that the Pi4 with 32 bit kernel has about
> > double performance compared to 64 bit kernel!!!
> >       
> Can be more specific about what benchmarks and who ran them?
> This seems highly unlikely.
>
>        Arnd
>
>