Re: [PATCH net] net: microchip: lan743x : bidirectional throughuput improvement

[Florian Fainelli]

On 10/4/23 12:20, Jakub Kicinski wrote:
> On Wed, 27 Sep 2023 16:46:23 +0530 Vishvambar Panth S wrote:
> > The LAN743x/PCI11xxx DMA descriptors are always 4 dwords long, but the
> > device supports placing the descriptors in memory back to back or
> > reserving space in between them using its DMA_DESCRIPTOR_SPACE (DSPACE)
> > configurable hardware setting. Currently DSPACE is unnecessarily set to
> > match the host's L1 cache line size, resulting in space reserved in
> > between descriptors in most platforms and causing a suboptimal behavior
> > (single PCIe Mem transaction per descriptor). By changing the setting
> > to DSPACE=16 many descriptors can be packed in a single PCIe Mem
> > transaction resulting in a massive performance improvement in
> > bidirectional tests without any negative effects.
> > Tested and verified improvements on x64 PC and several ARM platforms
> > (typical data below)
>
> Nobody complained for 5 years, and it's not a regression.
> Let's not treat this as a fix, please repost without the Fixes tag for
> net-next.

As a driver maintainer, you may want to provide some guarantees to your 
end users/customers that from stable version X.Y.Z the performance 
issues have been fixed. Performance improvements are definitively border 
line in terms of being considered as bug fixes though.
--
Florian