netdev - Re: DDoS attack causing bad effect on conntrack searches

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Date:	Fri, 23 Apr 2010 09:55:50 +0200 (CEST)
From:	Jan Engelhardt <jengelh@...ozas.de>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	Jesper Dangaard Brouer <hawk@...u.dk>,
	Patrick McHardy <kaber@...sh.net>, hawk@...x.dk,
	Linux Kernel Network Hackers <netdev@...r.kernel.org>,
	Netfilter Developers <netfilter-devel@...r.kernel.org>
Subject: Re: DDoS attack causing bad effect on conntrack searches

On Friday 2010-04-23 09:46, Eric Dumazet wrote:

>Le vendredi 23 avril 2010 à 09:23 +0200, Jan Engelhardt a écrit :
>> On Thursday 2010-04-22 23:28, Jesper Dangaard Brouer wrote:
>> 
>> > On Thu, 22 Apr 2010, Eric Dumazet wrote:
>> >
>> >> What exact version of kernel are you running ?
>> >
>> > 2.6.31.7-pvlan2G #3 SMP PREEMPT
>> > 32-bit kernel with 2G kernel mem (you showed me that trick).
>> 
>> Since when is enabling 2G a trick? :)
>> There's CONFIG_VMSPLIT_2G (and 2G_OPT) for quite some time now.
>> 
>
>Yes, when you know it, its not a trick anymore :)
>
>Years ago, we had to manually change PAGE_OFFSET, and I remember some
>machines with PAGE_OFFSET 0xA0000000  (1.5 GB LOWMEM), 
>or 0xB0000000 (1.25 GB), (PAE off)

I notice that 0xB0000000, which is now known as LOWMEM_3G_OPT,
is only available when PAE is off. Would you know the reason for
that decision? Are some values unsuitable for PAE?


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