linux-kernel - Re: [NETFILTER] early

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Message-ID: <46822540.2010004@trash.net>
Date:	Wed, 27 Jun 2007 10:52:16 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	Vasily Averin <vvs@...ru>
CC:	Eric Dumazet <dada1@...mosbay.com>,
	"David S. Miller" <davem@...emloft.net>,
	netfilter-devel@...ts.netfilter.org, rusty@...tcorp.com.au,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	devel@...nvz.org, Jan Engelhardt <jengelh@...putergmbh.de>
Subject: Re: [NETFILTER] early_drop() imrovement (v4)

Vasily Averin wrote:
> When the number of conntracks is reached nf_conntrack_max limit, early_drop()
> tries to free one of already used conntracks. If it does not find any conntracks
> that may be freed, it leads to transmission errors.
> In current implementation the conntracks are searched in one hash bucket only.
> It have some drawbacks: if used hash bucket is empty we have not any chances to
> find something. On the other hand the hash bucket can contain a huge number of
> conntracks and its check can last a long time.
> The proposed patch limits the number of checked conntracks and allows to search
> conntracks in other hash buckets. As result in any case the search will have the
> same chances to free one of the conntracks and the check will not lead to long
> delays.


Thanks Vasily. I have some patches queued to convert all conntrack
hashes to hlists, which conflict with your patches. They need a bit
more work, I'll integrate your changes on top of them once I'm done.

BTW, I played around with your last patch yesterday and it shows
a big improvement when flooding the machine with new connections.
Previously about 5% of the (valid) new connections would get
dropped, with your patch not a single one :)

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