Possible memory leak on BIND 9.10.1-P1 running on FreeBSD 10.1-RELEASE-p4 - part 2

Daniel Ryslink daniel.ryslink at dialtelecom.cz
Wed Jan 28 10:47:17 UTC 2015


One more comment - ad process size, I did measure the process sizes via 
'top', and the excessive memory was really and without a doubt allocated 
by named. While the machine has only 2GB of RAM, top reported named has 
allocated much more than that, swap was in use and free swap was 
steadily diminishing.

The recommend I killed the named process, all the swap was suddenly 
free, and top reported large amount of Free memory that was not there 
the moment ago.

Look at this graph:

http://www.mujweb.cz/nakamura/dns/leak.png

The cliffs after the peaks correspond with manual restart of bind.

This is how the same machine memory allocation looks after downgrading 
to 9.9.6 during the Sunday evening:

http://www.mujweb.cz/nakamura/dns/noleak.png

Note the orange parts of the graph representing the Free memory in 
FreeBSD memory management system - before, the Free memory was quickly 
consumed after each named restart, but the situation is radically 
different now. The server still has a steady pool of Free memory, that 
means memory that was never used since the restart of the named, since 
FreeBSD marks most of the deallocated memory as Inactive and cleans it 
just moments before it's needed again.

That clearly means that the overall memory requirements are dramatically 
lower with 9.9.6, and also that these requirements do not grow with 
time, but remain stable on a resolver with the same volume and structure 
of queries, which is what one would expect.

I am sorry I cannot provide the xml statistics you asked for, but the 
data I provided in the leakinfo.tgz archive should be sufficient to 
prove there is indeed a memory leak.

-- 
Best Regards,
Daniel Ryšlink
System Administrator

Dial Telecom a. s.
Křižíkova 36a/237
186 00 Praha 3, Česká Republika
Tel.:+420.226204627
daniel.ryslink at dialtelecom.cz
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On 01/27/2015 06:46 AM, Mukund Sivaraman wrote:
> Hi Daniel
>
> On Mon, Jan 26, 2015 at 02:56:44PM +0100, Daniel Ryšlink wrote:
>> Downgraded to BIND 9.9.6, the leak is gone, using the same named.conf,
>> same HW, same environment.
>>
>> It is highly likely there is really a memory leak problem in Bind
>> 9.10.
> Because many of these reports are on FreeBSD 10 in a resolver
> configuration, we are checking to see if we are able to reproduce it
> there.
>
> Meanwhile, please can you enable statistics-channels in named.conf and
> send us a dump of the XML statistics along with process sizes reported
> by ps when named grows very large?
>
> 		Mukund



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