KVM Protecting host

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swallowtail
Posts: 96
Joined: 2009/04/18 04:48:27

KVM Protecting host

Post by swallowtail » 2011/08/28 11:39:50

Being a fairly long term Xen user, I am trying to now learn KVM.

On my old CentOS 5.6 server, after having been stung in the past by a runaway guest consuming host CPU time to the point of making the entire group unresponsive, I made some changes as advised at http://wiki.xensource.com/xenwiki/XenBestPractices - namely the following:

/etc/xen/xend-config.sxp:
(dom0-min-mem 512)
(auto-balloon-dom0 no)

Grub menu.lst:
kernel /xen.gz-2.6.18-238.19.1.el5 dom0_mem=512M loglvl=all guest_loglvl=all

And finally edit /etc/rc.local:
xm sched-credit -d Domain-0 -w 512

Those settings have on a couple of occasions now saved my host's CPU time, allowing me to kill a badly behaving guest.

So - my question is, are similar techniques required under KVM to protect the host's CPU time? My new server will not be oversubscribed for guest RAM, so I am planning on disabling swap as per comments here http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Virtualization/ch24s06.html. That will prevent the host from swapping guest processes to disk, thus helping maintain responsiveness, but the interwebs seems pretty thin on detail about CPU scheduling for a KVM host... anyone shed any light / recommendations?

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