Re: KVM got slow after adding more physical memory to host

Avi Kivity
2011-09-06T15:13:50Z

On 09/06/2011 05:02 PM, Nikola Ciprich wrote:
> Hello,
>
> I'm trying to solve quite a weird problem on one of our customers' box.
> It's quad core Xeon X3430 @ 2.40GHz, running 64bit centos with 2.6.38 (I also tried upgrading to
> 2.6.39).
> After increasing physical memory from 16 to 20GB, all guest got incredibly slow, starting just
> one windows or linux guest causes host to be quite slow, and quest seems to be even slower.
> hardware virtualisation is on, KVM is used, no relevant update since the update.
> here's about 3 seconds of kvm_stat:
>
> kvm_exit 659513 103922
> kvm_entry 659505 103920
> kvm_emulate_insn 631118 99344
> kvm_exit(IO_INSTRUCTION) 625223 98398
> kvm_userspace_exit 624979 98359
> kvm_pio 624970 98357

How many guests in there?

Please post a trace as per http://www.linux-kvm.org/page/Tracing.

> but according to atop, there is almost no I/O activity from guests, and running top in them
> shows them to really be idle...
> but they eat like 60-70% of host CPU core time each..
>
> Do You have any idea on what should I check?
> thanks a lot in advance

Please post /proc/mtrr and /proc/iomem.

--
error compiling committee.c: too many arguments to function