From: Luca MUSCARIELLO <luca.muscariello@orange.com>
To: Eric Dumazet <eric.dumazet@gmail.com>,
James Roberts <James.Roberts@inria.fr>
Cc: "aqm@ietf.org" <aqm@ietf.org>, bloat <bloat@lists.bufferbloat.net>
Subject: Re: [Bloat] [aqm] TSO sizing fixes and the new paced "fq" scheduler in Linux 3.12
Date: Wed, 25 Sep 2013 17:38:23 +0200 [thread overview]
Message-ID: <5243036F.90302@orange.com> (raw)
In-Reply-To: <1380122152.3165.156.camel@edumazet-glaptop>
Le 25/09/2013 17:15, Eric Dumazet a écrit :
> On Tue, 2013-09-24 at 14:25 +0200, James Roberts wrote:
>> No one responded to Luca's Sept 1 comment (on the bloat list) that the
>> new code seems to do tail drop rather than longest queue drop.
>>
>>
>> If this is so, bandwidth sharing will not be fair since FQ alone is
>> not enough. This was shown in the previously cited Bell Labs
>> paper : http://ect.bell-labs.com/who/stiliadi/papers/jsac99.pdf. The
>> following table is copied from the paper.
> This paper assumes TCP stack can push cwin packets in the queue.
> We no longer have this behavior with linux.
>
> If you have drops on FQ, then you have a serious problem with your
> settings.
>
> FQ is meant to be used on hosts, not on routers.
>
> For routers, fq_codel is fine.
>
> TCP Small Queues limits the number of packets in Qdisc for any tcp flow
> (2 packets). Default FQ setting allows 10000 packets.
>
> You can add tail drop on FQ if you really want, but I never had a single
> drop in my FQ settings, on 20Gbps links and thousands of flows.
>
> Therefore I did not add complexity to solve a non problem.
Then, I feel like FQ is a bad name to call this "newFQ".
It's an implementation of a fair TCP pacer. Which is very useful, but FQ
is kind of misleading, IMHO.
Luca
>
>
>
> _______________________________________________
> aqm mailing list
> aqm@ietf.org
> https://www.ietf.org/mailman/listinfo/aqm
--
France Telecom R&D - Orange Labs
MUSCARIELLO Luca - OLN/NMP/TRM
38 - 40, rue du General Leclerc
92794 Issy Les Moulineaux Cedex 9 - France
Tel : +33 (0)1 45 29 60 37
http://perso.rd.francetelecom.fr/muscariello
next prev parent reply other threads:[~2013-09-25 15:35 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-20 23:18 [Bloat] " Dave Taht
2013-09-24 12:25 ` [Bloat] [aqm] " James Roberts
2013-09-25 15:15 ` Eric Dumazet
2013-09-25 15:38 ` Luca MUSCARIELLO [this message]
2013-09-25 16:58 ` Eric Dumazet
2013-09-29 5:49 ` Dave Taht
2013-09-29 8:02 ` Alex Elsayed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://lists.bufferbloat.net/postorius/lists/bloat.lists.bufferbloat.net/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5243036F.90302@orange.com \
--to=luca.muscariello@orange.com \
--cc=James.Roberts@inria.fr \
--cc=aqm@ietf.org \
--cc=bloat@lists.bufferbloat.net \
--cc=eric.dumazet@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox