netdev - Re: [PATCH 1/2] cbq: incorrectly low bandwidth setting blocks limited traffic

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 for Android: free password hash cracker in your pocket

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

Message-ID: <53EB5DE8.7030302@cogentembedded.com>
Date:	Wed, 13 Aug 2014 16:45:28 +0400
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Vasily Averin <vvs@...allels.com>, netdev@...r.kernel.org,
	Jamal Hadi Salim <jhs@...atatu.com>,
	"David S. Miller" <davem@...emloft.net>
CC:	Alexey Kuznetsov <kuznet@....inr.ac.ru>
Subject: Re: [PATCH 1/2] cbq: incorrectly low bandwidth setting blocks limited
 traffic

Hello.

On 8/13/2014 4:38 PM, Vasily Averin wrote:

> Mainstream commit f0f6ee1f70c4eaab9d52cf7d255df4bd89f8d1c2 have side effect:

    Please also specify that commit's summary line in parens.

> if cbq bandwidth setting is less than real interface throughput
> non-limited traffic can delay limited traffic for a very long time.

> This happen because of q->now changes incorrectly in cbq_dequeue():
> in described scenario L2T is much greater than real time delay,
> and q->now gets an extra boost for each transmitted packet.

> Accumulated boost prevents update q->now, and blocked class can wait
> very long time until (q->now >= cl->undertime) will be true again.

> To fix the problem the patch updates q->now on each cbq_update() call.
> L2T-related pre-modification q->now was moved to cbq_update().

> My testing confirmed that it fixes the problem and did not discovered

   Discover.

> any side-effects.

> Signed-off-by: Vasily Averin <vvs@...nvz.org>

WBR, Sergei

--
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