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

[Denys Fedoryshchenko <denys@visp.net.lb>]

 On Thu, 19 May 2011 08:39:18 +0200, Eric Dumazet wrote:
> Le jeudi 19 mai 2011 à 09:35 +0300, Denys Fedoryshchenko a écrit :
>> Hi, again
>>
>>  Just tried to upgrade large NAS from 2.6.38.6 to 2.6.39-rc7-git11, 
>> and
>>  at same time enabling ipv6 on it.
>>  Got that, after ppp2897 brought up (sure it means there is other 
>> 2896
>>  available, and also few ethernet vlans, around 32).
>>  I am not sure it is a bug, but it looks i had free memory(the box 
>> had
>>  8GB free), and lowmem too, also i will try to enable there 64bit 
>> kernel
>>  at evening.
>>
>>  May 17 16:00:42 194.146.155.70 kernel: [14925.897799] PERCPU:
>>  allocation failed, size=2048 align=4, failed to allocate new chunk
>>  May 17 16:00:42 194.146.155.70 kernel: [14925.898163] Pid: 24207, 
>> comm:
>>  pppd Not tainted 2.6.39-rc7-git11-build-0058 #4
>
> 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.
>
 Yes, it matches, i guess.
 CONFIG_NR_CPUS=8

 processor       : 7
 vendor_id       : GenuineIntel
 cpu family      : 6
 model           : 26
 model name      : Intel(R) Core(TM) i7 CPU         950  @ 3.07GHz

 Thanks. Then i will simply switch kernel to 64bit, but for now with 
 32bit userspace, since this semi-embedded system
 mass deployed, and i have to maintain it alone (cannot handle both 
 32/64 bit userspace), and some pc's don't have
 lm flag in cpuinfo :)

 I am hitting a lot lowmem limits lately, but the only application that 
 was not working right 32bit userspace/64bit kernel - ipvsadm.
 Should i report it as a bug (i will check if it is still an issue)?