feedback on ldap improvement in samba 4.11

Andrew Bartlett abartlet at samba.org
Tue Nov 19 20:25:31 UTC 2019


We can't ignore SIGKILL, which is why the OOM killer uses it.

What is being asked for is to add SIGKILL to the list of signals
eligible for a restart in prefork_child_pipe_handler. 

Andrew Bartlett

On Wed, 2019-11-20 at 09:10 +1300, Gary Lockyer via samba-technical
wrote:
> Yeah still a little reluctant about having processes ignoring
> SIGKILL,
> but given that we use the control pipes to shut down it should
> probably
> be ok.  It's just going to require a bit of thought to make sure
> things
> can be shut down.
> 
> Ngā mihi
> Gary
> On 20/11/19 08:53, Andrew Bartlett via samba-technical wrote:
> > On Wed, 2019-11-13 at 11:24 +0100, Denis Cardon via samba-technical
> > wrote:
> > > Hi everyone,
> > > 
> > > I just wanted to say how impressed I was with the improvement in
> > > memory 
> > > handling in ldap server in samba 4.11 that were announced in the
> > > changelog.
> > > 
> > > I was doing some debug on OOMKiller issues on a Samba-AD 4.9 with
> > > a 
> > > large database in production. There are some buggy softwares that
> > > make 
> > > queries for all users (the most peculiar one I have seen is a
> > > print 
> > > driver...) and Samba 4.9 properly handles the query but allocate
> > > around 
> > > 2GiB RAM for the query while the client downloads the result.
> > > With a 
> > > handfull of such queries piling up it can quickly run the server
> > > out
> > > of 
> > > memory.
> > > 
> > > On the other hand with Samba-4.11 memory is allocated in a much
> > > more 
> > > frugal way and it can handle hundred of such buggy queries
> > > without 
> > > crashing (it may be slow but it does not crash). So kudos the
> > > Catalyst 
> > > dev team for that great piece of work!
> > 
> > Thank you so much!  This work started long, long ago when Simo (at
> > the
> > time controversially) made ldb async, so it was really nice to be
> > able
> > to finish the job and see the end result finally show in something
> > so
> > valuable. 
> > 
> > When we did it, we were not sure that it would help outside our
> > synthetic benchmarks, so to hear the difference it makes in the
> > real
> > world is wonderful!
> > 
> > > About the prefork model, the master ldap process is properly
> > > restarting 
> > > the child process after a SIGTERM but it is not restarting after
> > > a 
> > > SIGKILL. Is it normal?
> > 
> > I get Gary's view about a manual kill -9 respawing perhaps being
> > unwanted, but I agree, a re-spawn system that doesn't cope with the
> > OOM
> > killer is less than ideal, I would have expected such a process to
> > be
> > restarted (perhaps after a bit longer wait). 
> > 
> > Andrew Bartlett
> > 
> 
> 
-- 
Andrew Bartlett
https://samba.org/~abartlet/
Authentication Developer, Samba Team         https://samba.org
Samba Development and Support, Catalyst IT   
https://catalyst.net.nz/services/samba








More information about the samba-technical mailing list