netdev - Re: conntrack timers usage

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Date:	Mon, 13 Oct 2008 15:20:39 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	Denys Fedoryshchenko <denys@...p.net.lb>
CC:	netdev@...r.kernel.org, netfilter@...r.kernel.org,
	Netfilter Development Mailinglist 
	<netfilter-devel@...r.kernel.org>
Subject: Re: conntrack timers usage

Denys Fedoryshchenko wrote:
> The story with excessive timers usage continue.
> 
> Here is my results from /proc/timer_stats for 30 seconds (150Mbps traffic)
> ...
> And here is netfilter usage, looks like ....
> I did also sysctl -w net.netfilter.nf_conntrack_acct=0
> 
>    1,     0 swapper          __nf_ct_refresh_acct (death_by_timeout)
>     1,     0 swapper          __nf_ct_refresh_acct (death_by_timeout)
>     1,     0 swapper          __nf_ct_refresh_acct (death_by_timeout)
>     1,     0 swapper          __nf_ct_refresh_acct (death_by_timeout)
>     1,     0 swapper          __nf_ct_refresh_acct (death_by_timeout)
>     1,     0 swapper          __nf_conntrack_confirm (death_by_timeout)
>     1,     0 swapper          __nf_conntrack_confirm (death_by_timeout)
>     1,     0 swapper          __nf_conntrack_confirm (death_by_timeout)
>     1,     0 swapper          __nf_conntrack_confirm (death_by_timeout)
>     1,     0 swapper          __nf_conntrack_confirm (death_by_timeout)
>     1,     0 swapper          __nf_conntrack_confirm (death_by_timeout)
>     1,     0 swapper          __nf_conntrack_confirm (death_by_timeout)
>     1,     0 swapper          __nf_conntrack_confirm (death_by_timeout)
> ....
> 
> Router-Dora ~ # cat /proc/timer_stats |grep '__nf'|wc -l
> 1005
> 
> Is it important to do so much calls to timers in conntrack?
> Precision on it is not more than 1 second.

There's one timer per conntrack. As you noticed, we only update
timers for delta >= 1s, but with many conntracks, that still adds
up to a lot.
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