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

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Message-ID: <10f61af229a48d77d06d154b4647cdde@visp.net.lb>
Date:	Thu, 19 May 2011 10:28:26 +0300
From:	Denys Fedoryshchenko <denys@...p.net.lb>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	<netdev@...r.kernel.org>
Subject: Re: 2.6.39-rc7-git11, x86/32, failed on ppp2897'th interface,  PERCPU:  allocation failed

 On Thu, 19 May 2011 08:55:13 +0200, Eric Dumazet wrote:
> 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))
 1920 +
 256 +
 208 = 2386 * 3000ppp's = 7152000, i think it is not that much at any 
 case, if i am not wrong.

 But at any case i will try 64bit.

>
> 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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