From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <toke@toke.dk>
Received: from mail.toke.dk (mail.toke.dk [IPv6:2001:470:dc45:1000::1])
 (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits))
 (No client certificate requested)
 by lists.bufferbloat.net (Postfix) with ESMTPS id 98BDC3CB35
 for <bloat@lists.bufferbloat.net>; Fri, 24 Aug 2018 07:24:44 -0400 (EDT)
From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@toke.dk>
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=toke.dk; s=20161023;
 t=1535109883; bh=hEr9pJ34P49IMh4YhtR0bCbL1eFJCoQiBSUtHY8X6gs=;
 h=From:To:Cc:Subject:In-Reply-To:References:Date:From;
 b=LzHRXymb/Leo7D+7X9XiLe0EaU8HrA12nSICrhxdG7aq0ttQSuo9jW+/mz+tFcqd3
 kNyP2Yf+9CTmfvR+JCyNaXd2DvtISabSx/kPJdGRbv7DEw3y2w8P3A6nB/owvNIRQV
 HfH13tLwPpwjh1eBUOhzqyxjKPUc2DzUKDsU8et3A6Xpj0nPH++dTJ1sX1/URfFriu
 temJdlci/kI5liUvEdIv8s4Qe+czBASlptTMCgLBEMoBqYOvbnUULa+7m6JoqNmpSA
 s4EH4mewuy8dOGgHEpGfOt+XB52HFBvj7/IXYsdQUY0XHf9mHA3pzxZAOVi1AAwkW3
 tw7EXucll4f2w==
To: Mikael Abrahamsson <swmike@swm.pp.se>, Dave Taht <dave.taht@gmail.com>
Cc: bloat <bloat@lists.bufferbloat.net>
In-Reply-To: <alpine.DEB.2.20.1808240901240.23215@uplift.swm.pp.se>
References: <CAA93jw7_FUA=LYdPFoy4TE5pbYJFuWb6fMreJFRUPK4xLBA76A@mail.gmail.com>
 <alpine.DEB.2.20.1808230746320.19688@uplift.swm.pp.se>
 <F508D2DC-474B-4E90-BDEC-97874A4E9194@gmx.de>
 <66e2374b-f998-b132-410e-46c9089bb06b@gmail.com>
 <360212B1-8411-4ED0-877A-92E59070F518@gmx.de>
 <alpine.DEB.2.20.1808231719250.23215@uplift.swm.pp.se>
 <CAKxU2N8oyeAa+cfzuu3sniQd4DnWyjnJsShnTtMTszj1uoLcZg@mail.gmail.com>
 <alpine.DEB.2.20.1808231949030.23215@uplift.swm.pp.se>
 <CAA93jw4qV6ieT-uaNp_vWBoptGZiHBv6u_W6c+UmArjvArrbBA@mail.gmail.com>
 <CAA93jw6Hd5PTvB84CanUdMZaxgFxxqxavGB7wSbxO_0oahk=JQ@mail.gmail.com>
 <alpine.DEB.2.20.1808240901240.23215@uplift.swm.pp.se>
Date: Fri, 24 Aug 2018 13:24:42 +0200
X-Clacks-Overhead: GNU Terry Pratchett
Message-ID: <87mutc6m85.fsf@toke.dk>
MIME-Version: 1.0
Content-Type: text/plain
Subject: Re: [Bloat] [Cerowrt-devel] beating the drum for BQL
X-BeenThere: bloat@lists.bufferbloat.net
X-Mailman-Version: 2.1.20
Precedence: list
List-Id: General list for discussing Bufferbloat <bloat.lists.bufferbloat.net>
List-Unsubscribe: <https://lists.bufferbloat.net/options/bloat>,
 <mailto:bloat-request@lists.bufferbloat.net?subject=unsubscribe>
List-Archive: <https://lists.bufferbloat.net/pipermail/bloat>
List-Post: <mailto:bloat@lists.bufferbloat.net>
List-Help: <mailto:bloat-request@lists.bufferbloat.net?subject=help>
List-Subscribe: <https://lists.bufferbloat.net/listinfo/bloat>,
 <mailto:bloat-request@lists.bufferbloat.net?subject=subscribe>
X-List-Received-Date: Fri, 24 Aug 2018 11:24:44 -0000

Mikael Abrahamsson <swmike@swm.pp.se> writes:

> On Thu, 23 Aug 2018, Dave Taht wrote:
>
>> I should also point out that the kinds of routing latency numbers in
>> those blog entries was on very high end intel hardware. It would be
>> good to re-run those sort of tests on the armada and others for
>> 1,10,100, 1000 routes. Clever complicated algorithms have a tendency
>> to bloat icache and cost more than they are worth, fairly often, on
>> hardware that typically has 32k i/d caches, and a small L2.
>
> My testing has been on OpenWrt with 4.14 on intel x86-64. Looking how the 
> box behaves, I'd say it's limited by context switching / interrupt load, 
> and not actually by CPU being busy doing "hard work".
>
> All of the fast routing implementations (snabbswitch, FD.IO/VPP etc)
> they take away CPU and devices from Linux, and runs busy-loop with
> polling a lot of the time, an never context switching which means L1
> cache is never churned. This is how they become fast. I see potential
> to do "XDP offload" of forwarding here, basically doing similar job to
> what a hardware packet accelerator does.

Yup, that would help; we see basically 2-3x improvement in routing
performance with XDP over the regular stack. Don't think there's XDP
support in any of the low-end ethernet drivers yet, though...

-Toke