Re: ARM router NAT performance affected by random/unrelated commits

[RafaÅ MiÅecki]

On Tue, 21 May 2019 at 12:45, Russell King - ARM Linux admin
<linux@xxxxxxxxxxxxxxx> wrote:
> On Tue, May 21, 2019 at 12:28:48PM +0200, RafaÅ MiÅecki wrote:
> > I work on home routers based on Broadcom's Northstar SoCs. Those devices
> > have ARM Cortex-A9 and most of them are dual-core.
> >
> > As for home routers, my main concern is network performance. That CPU
> > isn't powerful enough to handle gigabit traffic so all kind of
> > optimizations do matter. I noticed some unexpected changes in NAT
> > performance when switching between kernels.
> >
> > My hardware is BCM47094 SoC (dual core ARM) with integrated network
> > controller and external BCM53012 switch.
>
> Guessing, I'd say it's to do with the placement of code wrt cachelines.

That was my guess as well, that's why I tried "cachestat" tool.


> You could try aligning some of the cache flushing code to a cache line
> and see what effect that has.

Can you give me some extra hint on how to do that, please? I tried
searching for it a bit but I didn't find any clear article on that
matter.

-- 
RafaÅ