[Dovecot] Ongoing performance issues with 2.0.x

Udo Wolter udo.wolter at charite.de
Mon Nov 8 12:45:06 EET 2010

* Ralf Hildebrandt <Ralf.Hildebrandt at charite.de>:
> > And I'm guessing you're running a 32bit PAE kernel because VMWare ESX
> > still doesn't officially support 64bit guests, correct?
> No, it's supported, but I don'T want to change the whole system.

That's right, we cannot switch without having several hours downtime. This is
not acceptable. I'm thinking of a way for switching to 64 bit with exchanging
disks etc. But I don't know if this will work, I have to test it first.
> > Is this the only guest on this host or do you have others?
> only guest

Yes, the VM-system has 8 CPUs and that's all the ESX has. Of course, there are
times, when the ESX doesn't have that much stress so the DRS moves 1 or 2 other
machines onto it. But since we got that high load, the rest of the machines all
had been moved off the ESX.

> > If this is the only guest, you have 2 dual core dies in that Xeon CPU,
> > 4 cores total.  I assume you've assigned 4 virtual CPUs to this Debian
> > VM?
> Yes, something like that


> > You may want to run top in the hypervisor console itself (or an SSH
> > session into the hypervisor) and watch the %CPU of the hypervisor's
> > kernel threads.  That might tell us something as well.
> Udo has to answer that, but from what he told me it was fully using
> all cpus with 2.0, and now it's idling with 1.2
> More details to follow (from him)

As I said in the other mail: as long as the load isn't high enough we cannot
see any problems in the ESX. Only, if we step over some kind of specific
barrier. I think, it's when even the ESX runs out of possibilities to handle so
many interrupts.


Udo Wolter
  Geschäftsbereich IT | Abt. System
  Charité - Universitätsmedizin Berlin
  Campus Benjamin Franklin
  Hindenburgdamm 30 | D-12203 Berlin
  Tel. +49 30 450 570847 | Fax +49 30 450 7570600
  Udo.Wolter at Charite.de | http://www.charite.de

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