Re: [PATCH 3/3] arm64: use runtime constant to optimize handle_arch_irq access

[Jisheng Zhang <jszhang@kernel.org>]

On Mon, Feb 23, 2026 at 09:15:47AM +0000, Leo Yan wrote:
> On Sat, Feb 21, 2026 at 08:14:17AM +0800, Jisheng Zhang wrote:
> 
> [...]
> 
> > On Fri, Feb 20, 2026 at 04:47:38PM +0000, Leo Yan wrote:
> > > On Fri, Feb 20, 2026 at 09:34:14PM +0800, Jisheng Zhang wrote:
> > > 
> > > [...]
> > > 
> > > > > > Run 3 iterations, and measures three metrics (messaging/pipe/seccomp)
> > > > > > and results in seconds. Less is better.
> > > > > > 
> > > > > >   +---------------------+--------+--------+--------+--------+
> > > > > >   |Without change       |   run1 |   run2 |   run3 |    avg |
> > > > > >   +---------------------+--------+--------+--------+--------+
> > > > > >   |messaging (sec)      |  4.546 |  4.508 |  4.591 |  4.548 |
> > > > > >   |pipe (sec)           | 24.258 | 24.224 | 24.017 | 24.166 |
> > > > > >   |seccomp-notify (sec) | 48.393 | 48.457 | 48.232 | 48.361 |
> > > > > >   +---------------------+--------+--------+--------+--------+
> > > > > > 
> > > > > >   +---------------------+--------+--------+--------+--------+--------+
> > > > > >   |With change          |   run1 |   run2 |   run3 |    avg |   diff |
> > > > > >   +---------------------+--------+--------+--------+--------+--------+
> > > > > >   |messaging (sec)      |  4.493 |  4.523 |  4.556 |  4.524 | +0.52% |
> > > > > >   |pipe (sec)           | 23.159 | 23.702 | 28.649 | 25.170 | -4.15% |
> > > > > 
> > > > > If you check the result, this result variance is abnormal, it means
> > > > > your OS is noiser.
> > > > 
> > > > BTW: if you remove the abnormal run3 result, you'll find that the
> > > > benchmark is improved by ~3.5% on CA73:
> > > > (23.159 + 23.702) / 2 = 23.43
> > > > (24.258 + 24.224) / 2 = 24.24
> > > > (24.24 - 23.43)*100 / 23.43 = ~3.5
> > > 
> > > TBH, I don't think we should subjectively select data.  But I agree a
> > 
> > The precondition of this is testing the benchmark properly. And I just
> > tried perf bench sched in noisy OS, I didn't get the similar abnormal
> > variance as you got, so I think your run3 result was CA53's result.
> > This isn't an apple-to-apple comparison.
> 
> Not true.  As said, I tested on CA73.  I should say explicitly that I
> have hotplugged off CA53 CPUs and run test only on CA73 CPUs.

I tested on quad CA73 platform, I can reproduce the abnormal variance
as you got. This means the series may not alway improve performance
as I expected for *all* CPUs. So I'd like to drop it now.

> 
> > If possible, could you plz test after forcing CA53 offline or test on
> > non big.little platform. Anyway, I will test CA73 next week too.
> > 
> > > clean test env is important to avoid noise, and I also agree that the
> > > current results already show positive signals.
> > > 
> > > Thanks,
> > > Leo