From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH] net: bridge: add max_fdb_count Date: Thu, 16 Nov 2017 08:54:13 -0800 Message-ID: <20171116085413.3f23a7d6@xeon-e3> References: <1510774027-2468-1-git-send-email-srn@prgmr.com> <20171115120452.3b426442@xeon-e3> <20171116022540.GF2130@lunn.ch> <6c916129-5679-32bb-a3f1-46cc02c3683d@lab.ntt.co.jp> <257f3f74-8761-35ef-3b43-e2705d8510a6@prgmr.com> <88cc9135-0dd5-2849-7f63-86ebf98efd86@lab.ntt.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Toshiaki Makita , Sarah Newman , Andrew Lunn , netdev@vger.kernel.org To: Roopa Prabhu Return-path: Received: from mail-pg0-f66.google.com ([74.125.83.66]:49737 "EHLO mail-pg0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760209AbdKPQyS (ORCPT ); Thu, 16 Nov 2017 11:54:18 -0500 Received: by mail-pg0-f66.google.com with SMTP id 70so8493468pgf.6 for ; Thu, 16 Nov 2017 08:54:17 -0800 (PST) In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 15 Nov 2017 22:20:23 -0800 Roopa Prabhu wrote: > On Wed, Nov 15, 2017 at 10:13 PM, Toshiaki Makita > wrote: > > On 2017/11/16 13:54, Sarah Newman wrote: > >> On 11/15/2017 08:05 PM, Toshiaki Makita wrote: > >>> On 2017/11/16 11:25, Andrew Lunn wrote: > >>>>> Also what do the vendors using bridge for L2 offload to switch think? > >>>> > >>>> The Marvell L2 switches which DSA supports have 8K FDB/MDB entries. So > >>>> maybe 1024 is a bit low? > >>> > >>> How about U32_MAX by default since it is currently not restricted. > >>> (assuming the field will be changed to u32 as per Stephen's feedback). > >>> > >>> Otherwise users may suffer from unexpected behavior change by updating > >>> kernel? > >>> > >> > >> U32_MAX seems like much too high a default to be helpful to a typical user. How many devices are realistically on a single bridge in the wild? Double > >> that seems like a reasonable default. > > > > I'm suggesting the most unrealistic number to essentially disable the > > restriction by default. > > My understanding is that we put a priority on not to break existing > > users even if the new restriction looks reasonable for most people. > > +1 , and yes, 1024 is very low. some of the switches we use support > around 128K FDB entries and we have seen that number increase fairly > quickly in newer generation switches. Default should be no limit to > not break existing users. New features can not break existing users. My recommendation would be that 0 be used as a magic value to indicate no limit and that would be the default. Also the limit should be controllable on a per port of bridge (interface) basis.