netdev - Re: 2.6.39-rc7-git11, x86/32, failed on ppp2897'th interface, PERCPU: allocation failed

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Date:	Thu, 19 May 2011 08:55:13 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Denys Fedoryshchenko <denys@...p.net.lb>
Cc:	netdev@...r.kernel.org
Subject: Re: 2.6.39-rc7-git11, x86/32, failed on ppp2897'th interface,
 PERCPU:  allocation failed

Le jeudi 19 mai 2011 à 08:39 +0200, Eric Dumazet a écrit :

> Its a known problem : When ipv6 is enabled, we allocate percpu memory to
> hold per device snmp counters.
> 
> make sure kernel idea of max possible cpus matches real number of cpus.
> 
> And yes, switching to 64bit kernel helps a lot.
> 
> 

Looking at snmp6_alloc_dev(), we allocate three mib per device :

ipstats_mib  (30 * sizeof(u64) * number_of_possible_cpus)
icmpv6_mib    (4 * sizeof(long) * number_of_possible_cpus)
icmpv6msg_mib  (26 * sizeof(long))

For sure icmp ones dont need percpu counter. Plain atomic_long_t
(shared) would be enough, since ICMP messages are rare enough.



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