Re: [patch net-next v4 00/12] sched: introduce chain templates support with offloading to mlxsw

[David Miller <davem@davemloft.net>]

From: Jiri Pirko <jiri@resnulli.us>
Date: Mon, 23 Jul 2018 09:23:03 +0200

> For the TC clsact offload these days, some of HW drivers need
> to hold a magic ball. The reason is, with the first inserted rule inside
> HW they need to guess what fields will be used for the matching. If
> later on this guess proves to be wrong and user adds a filter with a
> different field to match, there's a problem. Mlxsw resolves it now with
> couple of patterns. Those try to cover as many match fields as possible.
> This aproach is far from optimal, both performance-wise and scale-wise.
> Also, there is a combination of filters that in certain order won't
> succeed.
> 
> Most of the time, when user inserts filters in chain, he knows right away
> how the filters are going to look like - what type and option will they
> have. For example, he knows that he will only insert filters of type
> flower matching destination IP address. He can specify a template that
> would cover all the filters in the chain.
> 
> This patchset is providing the possibility to user to provide such
> template to kernel and propagate it all the way down to device
> drivers.

I just want to say I like how small the mlxsw driver patch is :-)