[Samba] gencache.tdb size and cache flush

[Volker Lendecke]

On Tue, Sep 04, 2018 at 11:59:04AM +0200, Francesco Malvezzi wrote:
> Il 04/09/18 06:00, Volker Lendecke ha scritto:
> > Hi!
> > 
> > Technical description below, but the exec summary is: Yes, we have a
> > performance problem with gencache.
> > 
> > On Wed, Aug 29, 2018 at 10:28:05AM +0200, Francesco Malvezzi via samba wrote:
> >> Hi all,
> >>
> >> I have a midsize AD domain with some 50k users but only 100 workstations
> >> joined.
> >>
> >> Sometimes I find server CPU throttling at 100%. In order to let it drop
> > 
> > Can you find out where *exactly* that 100% is spent? gstack on the
> > spinning process with debug symbols would be very helpful here.
> 
> not sure how to do it.
> 
> can be like that
> https://gist.github.com/francescm/8e396f5470da8df8451be13777e18810
> ?

Yes, exactly. The relevant line is

#19 0x00007fe50c1c5a3c in dcesrv_samr_EnumDomainUsers

which means that some client is listing all users in your domain. With
50.000 users this takes a while. If the client times out and
reconnects, this can pretty quickly pile up.

Do you have Linux clients with winbind and "winbind enum users = yes"
in your network? This would probably do that to your DC.

Volker

-- 
SerNet GmbH, Bahnhofsallee 1b, 37081 Göttingen
phone: +49-551-370000-0, fax: +49-551-370000-9
AG Göttingen, HRB 2816, GF: Dr. Johannes Loxen
http://www.sernet.de, mailto:kontakt at sernet.de

Meet us at Storage Developer Conference (SDC)
Santa Clara, CA USA, September 24th-27th 2018