netdev - Re: inaccurate packet scheduling

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20121218104350.6aec09fd@nehalam.linuxnetplumber.net>
Date:	Tue, 18 Dec 2012 10:43:50 -0800
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Jiri Pirko <jiri@...nulli.us>
Cc:	Eric Dumazet <edumazet@...gle.com>,
	Stephen Hemminger <stephen.hemminger@...tta.com>,
	jhs@...atatu.com, davem@...emloft.net, tgraf@...g.ch,
	netdev@...r.kernel.org
Subject: Re: inaccurate packet scheduling

On Tue, 18 Dec 2012 19:40:36 +0100
Jiri Pirko <jiri@...nulli.us> wrote:

> Tue, Dec 18, 2012 at 07:06:53PM CET, edumazet@...gle.com wrote:
> >> No such messages in log
> >>
> >>>Also turn off TSO since it screws up any form of rate control.
> >>
> >> Turning off TSO did not help. However, turning off scatter-gather
> >> helped, on both HP DL360G8 (igb) and IBM JS22 (ehea).
> >>
> >
> >Think to also disable GSO
> 
> On rhel6 kernel (2.6.32-based) I have to disable GSO as well.
> 
> The question is: Is this a bug or is it mandatory to get this offload
> disabled in order to TBF to be working correctly?
> 
> Thanks a bunch.
> 
> Jiri
> 
> >
> >Alternatively, you can use "mtu 65536" to allow TBF to send packets
> >bigger than 2048 bytes

It is really a bug. The packet schedulers mostly assume that a single
skb results in a single packet, and that the skb->len equals the size
of the packet on the wire.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html