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

[Russell King - ARM Linux admin]

On Tue, May 21, 2019 at 12:28:48PM +0200, RafaÅ MiÅecki wrote:
> Hi,
> 
> 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.
You could try aligning some of the cache flushing code to a cache line
and see what effect that has.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up