Re: [tor-relays] Out of memory message

[Logforme <m7527@xxxxxx>]

On 2014-12-15 19:43, Nick Mathewson wrote:
> On Wed, Dec 10, 2014 at 2:31 AM, Roger Dingledine <arma@xxxxxxx> wrote:
>> On Sun, Dec 07, 2014 at 01:43:46PM +0100, Logforme wrote:
>>> To me it looks like an attacker that ramped up over a 6 hour period and
>>> then stopped building new circuits. Since the tor process still uses all
>>> available memory (more than 24 hours later) I guess the attacker still
>>> holds some circuits open.
>> Careful with your conclusion there -- because of memory fragmentation, the
>> process can still hold the memory even when Tor has freed the memory. That
>> happens because some part of the memory page is in use and some is freed,
>> but since not all of it is freed the allocator doesn't take it back.
>>
>> Some quick searches point to
>> https://www.ibm.com/developerworks/community/blogs/kevgrig/entry/linux_native_memory_fragmentation_and_process_size_growth
>> as what looks like a nice summary of the issue.
>>
>> --Roger
> If this *is* memory fragmentation, one possible reason why it would
> have started appearing recently might be that we turned the freelist
> code off by default in 0.2.5, on the theory that it should be safer to
> do that than not.
>
> https://trac.torproject.org/projects/tor/ticket/11476 has more
> background here.  I don't think it's the likeliest explanation, but
> it's worth examining.
>
> Are the people experiencing this issue using similar allocators?
>

I don't build Tor myself, I use the latest debian package:
0.2.5.10-1~d70. No idea how that is built.

I have not restarted Tor so it is still hogging all ram + swap (relay
works fine so no reason to restart). If there is anything I can run to
get more information about what has happened (code dump maybe?), I'm
happy to do so.

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