Re: [PATCH 10/11] sched_ext: scx_qmap: Add proxy execution support

[John Stultz]

On Sat, Jul 18, 2026 at 1:24 AM Andrea Righi <arighi@xxxxxxxxxx> wrote:
> On Fri, Jul 17, 2026 at 11:04:16PM -0700, John Stultz wrote:
> > On Fri, Jul 17, 2026 at 10:47 PM Andrea Righi <arighi@xxxxxxxxxx> wrote:
> > > This looks like something related to BPF arena pointers and incorrectly
> > > generated BPF code (the other schedulers don't use BPF arenas, so that'd explain
> > > why you only see this with scx_qmap).
> > >
> > > Which version of clang are you using?
> >
> > Debian clang version 19.1.7 (3+b1)
> >
> > Running in a debian 13 vm.   Though I'm using gcc normally for my
> > builds (but I see the tools/sched_ext/ build does use clang explicitly
> > for some things).
>
> Yeah, we explicitly use clang to build BPF code. I'm on CachyOS, which ships
> clang 22.1.8. In theory clang-19 should be enough... if you can mess up the VM
> maybe give it a try with clang 20? From the dump it really looks like the
> compiler failed to generate proper BPF code for arenas.

Looks like you're right. Using a 23.0.0git checkout it seems like its
working better there.

Thanks for walking me through this :)
-john