[Samba] Samba 4.9.4 - high RAM usage - OOM killer

Tim Beale timbeale at catalyst.net.nz
Mon Jan 28 20:53:56 UTC 2019


It looks like what is happening is the Samba RPC server is forking a
separate process for each NETLOGON connection it accepts. Normally, when
the connection is closed, the child process will be cleaned up. On your
setup, the connections appear to be left open (presumably due to the
constant mail SSO queries), and so the rpc_server processes just
accumulate. You had 669 rpc_server processes, which sounds like roughly
one per user.

On Samba v4.10, there will be better handling of these NETLOGON
connections using the prefork process model. Instead of forking a
separate process for each NETLOGON connection, a set number of worker
processes will be pre-forked when samba first starts up, and the RPC
connections will be shared amongst these worker processes. To use
prefork, specify '--model=prefork' as arguments when starting Samba.

Unfortunately, the scheduled release date for v4.10 isn't until 5 March
2019. Note that the prefork option does exist in v4.9, however, there is
no prefork support in 4.9 for the RPC server process. I'm not sure what
you can do in the meantime, other than restart the DCs regularly.

Best regards,

On 29/01/19 5:19 AM, Laurent CARON via samba wrote:
> Hi Denis,
>> could you please take a look at which process is taking so much RAM?
>> Is there a pile of smbd process around? If you are using Bind-dlz,
>> how much memory named is eating? Is is the increase in RAM
>> consumption is linear over time?
>> If it is a "samba" process that is eating all the RAM, please check
>> the PID and the samba-tool processes command to report which part of
>> samba is weaking havoc the system.
>> I'd say you should be fine with 4GiB with such a setup...
> Seems lots of samba processes related to rpc_server are making the
> server crawl (please see attachment) after just 6 days of uptime.
> I can provide a strace of the most CPU/IO hungry process upon request.
> Thanks
> Laurent

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