Re: [PATCH v3 2/6] futex2: Implement vectorized wait

[Arnd Bergmann]

On Thu, Sep 16, 2021 at 1:22 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> On Thu, Sep 16, 2021 at 12:10:25AM -0400, Gabriel Krisman Bertazi wrote:
>
> > I find this weird.  I'm not even juts talking about compat, but even on
> > native 32-bit. But also, 32 applications on 64, which is a big use
> > case for games.
>
> Seriously, people still make 32bit applications today? And for legacy
> games, I would think the speed increase of modern CPUs would far offset
> this little inefficiency.

There are 32-bit Windows games apparently, because it's easier to build it
that way than having both 32-bit and 64-bit versions.
There may be native 32-bit games built for Linux from the same sources when
that is not written portably, not sure if that's a thing.

One important reason to use compat mode is for cost savings when you can
ship an embedded system with slightly less RAM by running 32-bit user space
on it. We even still see people running 32-bit kernels on Arm boxes that have
entry-level 64-bit chips, though I hope that those will migrate the
kernel to arm64
even when they ship 32-bit user space.

Similar logic applies to cloud instances or containers. Running a 32-bit
Alpine Linux in a container means you can often go to a lower memory
instance on the host compared to a full 64-bit distro.

        Arnd