netdev - Re: OOM when adding ipv6 route: How to make available more per-cpu memory?

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Date:	Mon, 08 Nov 2010 12:02:11 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ben Greear <greearb@...delatech.com>
Cc:	NetDev <netdev@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>
Subject: Re: OOM when adding ipv6 route:  How to make available more
 per-cpu memory?

Le samedi 06 novembre 2010 à 10:08 -0700, Ben Greear a écrit :

> At least I don't see any percpu dumps in dmesg.  I vaguely remember
> someone posting some ipv6 address scalability patches some time back.
> I think they had to hack on /proc fs as well.  I'll see if I can
> dig those up.
> 
> > Make sure udev / hotplug is not the problem, if you create your devices
> > very fast.
> 
> We can create the macvlans w/out problem, though I'm sure that could
> be sped up.  The problem is when we try to add IPv6 addresses to
> them.

I see. Did you check /proc/sys/net/ipv6/ tunables ?

For example, I bet you need to make route/max_size a bigger value than
default (4096)

Following is working for me

echo 16384 >/proc/sys/net/ipv6/route/max_size
modprobe dummy numdummies=2000
for a in `seq 1 1999`
do
 ip -6 add add 4444::444:$a/24 dev dummy$a
done

ip -6 ro | wc -l
6008



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