netdev - Re: [Bugme-new] [Bug 38102] New: BUG kmalloc-2048: Poison overwritten

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Message-ID: <CAB9v_DHuFkymU1a-tfVcpT62y2anWw-HWPtK8WF4T5Wr+-C8mg@mail.gmail.com>
Date:	Tue, 5 Jul 2011 08:18:27 +0400
From:	Alexey Zaytsev <alexey.zaytsev@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Michael Büsch <m@...s.ch>,
	Andrew Morton <akpm@...ux-foundation.org>,
	netdev@...r.kernel.org, Gary Zambrano <zambrano@...adcom.com>,
	bugme-daemon@...zilla.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Pekka Pietikainen <pp@...oulu.fi>,
	Florian Schirmer <jolt@...box.org>,
	Felix Fietkau <nbd@...nwrt.org>, Michael Buesch <mb@...sch.de>
Subject: Re: [Bugme-new] [Bug 38102] New: BUG kmalloc-2048: Poison overwritten

On Tue, Jul 5, 2011 at 08:17, Alexey Zaytsev <alexey.zaytsev@...il.com> wrote:
> On Tue, Jul 5, 2011 at 08:14, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> Le mardi 05 juillet 2011 à 06:11 +0200, Eric Dumazet a écrit :
>>> Le mardi 05 juillet 2011 à 07:56 +0400, Alexey Zaytsev a écrit :
>>> > On Tue, Jul 5, 2011 at 07:44, Eric Dumazet <eric.dumazet@...il.com> wrote:
>>> > >
>>> > > I dont care about duplicate acks at this point.
>>> > >
>>> > > Thats a separate issue (TCP layer)
>>> > >
>>> >
>>> > Maybe some tx packets are just sent out more then once? Or a single
>>> > packet is sent out instead of some other packets?
>>> > The delays between two dups is short, and they come in bursts, up to a
>>> > few hundreds of duplicate packets at a time.
>>> >
>>>
>>> Thats a completely different problem. SSH is very expensive for your
>>> receiver (your dump1 file has small packets (560 bytes)), and it cannot
>>> cope with the stress.
>>>
>>> You're filling the b44 rx ring, and b44 driver has no choice to zap 200
>>> packets at once. This sure is a problem for tcp, as it stalls the thing.
>>>
>>> You could avoid this by doing this at b44 machine (the receiver)
>>>
>>> echo "4096 32768 87380" >/proc/sys/net/ipv4/tcp_rmem
>>>
>>> So that sender wont be able to push so many packets
>>
>> You can also try using more packets in rx ring : (default is 200
>> packets, limit ~511)
>>
>> ethtool -G eth0 rx 400
>>
>>
> Check out starting at packet 302893. 383 _identical_ ACKs were sent
> out by the b44 machine within 30 milliseconds.

In dump1.pcap, that is.
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