Tue, Jun 26, 2018 at 09:00:45AM CEST, jakub.kicin...@netronome.com wrote: >On Mon, Jun 25, 2018 at 11:43 PM, Jiri Pirko <j...@resnulli.us> wrote: >> Tue, Jun 26, 2018 at 06:58:50AM CEST, jakub.kicin...@netronome.com wrote: >>>On Mon, 25 Jun 2018 23:01:39 +0200, Jiri Pirko wrote: >>>> From: Jiri Pirko <j...@mellanox.com> >>>> >>>> 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. >>> >>>Perhaps it's lack of sleep, but this paragraph threw me a little off >>>the track. IIUC the goal of this set is to provide a way to inform the >>>HW about expected matches before any rule is programmed into the HW. >>>Not before any rule is added to a particular chain. One can just use >>>the first rule in the chain to make a guess about the chain, but thanks >>>to this set user can configure *all* chains before any rules are added. >> >> The template is per-chain. User can use template for chain x and >> not-use it for chain y. Up to him. > >Makes sense. > >I can't help but wonder if it'd be better to associate the >constraints/rules with chains instead of creating a new "template" >object. It seems more natural to create a chain with specific >constraints in place than add and delete template of which there can >be at most one to a chain... Perhaps that's more about the user space >tc command line. Anyway, not a strong objection, just a thought.
Hmm. I don't think it is good idea. User should see the template in a "show" command per chain. We would have to have 2 show commands, one to list the template objects and one to list templates per chains. It makes things more complicated for no good reason. I think that this simple chain-lock is easier and serves the purpose. > >>>And that's needed because once any rule is added the tcam config can no >>>longer be easily modified? >> >> Yes.
