Re: [PATCH 00/19] arm64: Implement parallel CPU onlining with PSCI v0.2+

[Will Deacon]

On Tue, Sep 29, 2026 at 02:26:03PM +0530, Pankaj Patil wrote:
> On 9/7/2026 10:10 PM, Will Deacon wrote:
> > Hi folks,
> > 
> > This series implements CONFIG_HOTPLUG_PARALLEL for arm64 by utilising
> > the argument to CPU_ON introduced in PSCI v0.2. This supersedes the
> > previous series from Jinjie [1], and I'm grateful to him for his support
> > getting this alternative version in shape for posting.
> > 
> > I previously spoke at KVM forum about this work last year:
> > 
> >   https://www.youtube.com/watch?v=Q6kOshnnQuE
> > 
> > There are three major benefits realised by these changes:
> > 
> > 1. We ditch our home-brew secondary CPU synchronisation in favour of
> >    constructs in the core code.
> > 
> > 2. They offer a performance advantage on some platforms, where getting a
> >    CPU into the kernel can take time. I'm hoping Jinjie can provide
> >    numbers in this case.
> > 
> 
> Tested on Glymur-CRD - 18 core qcom,oryon-2-2 CPU, saw ~6% improvement
> in smp bringup and ~12% improvement in cpu hotplug kselftest
> 
> Tested-by: Pankaj Patil <pankaj.patil@xxxxxxxxxxxxxxxx>

Nice, thanks for giving this a go, Pankaj! I'll post a v2 soon, so it
would be great if you can try that as well.

Cheers,

Will