From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiri Pirko Subject: Re: [patch net-next 0/9] net: sched: introduce chain templates support with offloading to mlxsw Date: Tue, 26 Jun 2018 08:43:55 +0200 Message-ID: <20180626064355.GQ2161@nanopsycho> References: <20180625210148.9386-1-jiri@resnulli.us> <20180625215850.001276b8@cakuba.netronome.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, davem@davemloft.net, jhs@mojatatu.com, xiyou.wangcong@gmail.com, simon.horman@netronome.com, john.hurley@netronome.com, dsahern@gmail.com, mlxsw@mellanox.com To: Jakub Kicinski Return-path: Received: from mail-wr0-f195.google.com ([209.85.128.195]:36045 "EHLO mail-wr0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750942AbeFZGpQ (ORCPT ); Tue, 26 Jun 2018 02:45:16 -0400 Received: by mail-wr0-f195.google.com with SMTP id f16-v6so15971444wrm.3 for ; Mon, 25 Jun 2018 23:45:15 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20180625215850.001276b8@cakuba.netronome.com> Sender: netdev-owner@vger.kernel.org List-ID: Tue, Jun 26, 2018 at 06:58:50AM CEST, jakub.kicinski@netronome.com wrote: >On Mon, 25 Jun 2018 23:01:39 +0200, Jiri Pirko wrote: >> From: Jiri Pirko >> >> 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. > >And that's needed because once any rule is added the tcam config can no >longer be easily modified? Yes.