Re: [ovirt-devel] [ovirt-users] [SCALE][RFC] ksmd bound to one core

On 05.11.2014 21:07, Adam Litke wrote: > On 04/11/14 13:11 +0100, Sven Kieske wrote: >> Hi, >> >> currently ksmd is a single process >> and is thus bound to one core. >> >> This leads to some scaling problems such as: >> >> If you got a lot of vms on one host with huge amounts >> of ram you can observe that the cpu usage by ksmd >> goes easily to 100%. I wonder what would be the benefit here... I think spending CPU cycles on something like memory compression is not what (most) users would do.

Already I think this is an annoyance; maybe thats why the process is niced to +5. A multi process daemon would require careful confining (with cgroups). To my understanding the for KSM to really work well is to have many (idle / high mem) guests which are quite similar? >> >> I wonder if ksmd could not be split up >> in child/worker threads, thus enabling higher density >> of vms on one host. > > It's likely going to be trickier than you imagine with the added > locking that would be required to synchronize the ksmd threads. Actually I was refraining to answer Svens question since I lack some knowledge here. But I guessed synchronization was the reason for the single threadted design. Some serous work needs to be done on KSM do achieve this goal. I was thinking about some map/reduce aglo to do that... OTOH mangeling with mem pages of guests very requires special care. > >> >> or can this just be tweaked by altering values in >> /etc/ksmtuned.conf ? > > I don't think it can. > >> What do you think? > > Interesting idea. > -- Daniel Helgenberger m box bewegtbild GmbH P: +49/30/2408781-22 F: +49/30/2408781-10 ACKERSTR. 19 D-10115 BERLIN www.m-box.de www.monkeymen.tv Geschäftsführer: Martin Retschitzegger / Michaela Göllner Handeslregister: Amtsgericht Charlottenburg / HRB 112767 _______________________________________________ Devel mailing list Devel(a)ovirt.org http://lists.ovirt.org/mailman/listinfo/devel