Re: KVM with hugepages generate huge load with two guests

[Avi Kivity <avi@redhat.com>]

On 11/21/2010 02:24 AM, Dmitry Golubev wrote:
> Hi,
>
> Seems that nobody is interested in this bug :(
>

It's because the information is somewhat confused.  There's a way to 
prepare bug reports that gets developers competing to see who solves it 
first.


> Anyway I wanted to add a bit more to this investigation.
>
> Once I put "nohz=off highres=off clocksource=acpi_pm" in guest kernel
> options, the guests started to behave better - they do not stay in the
> slow state, but rather get there for some seconds (usually up to
> minute, but sometimes 2-3 minutes) and then get out of it (this cycle
> repeats once in a while - every approx 3-6 minutes). Once the
> situation became stable, so that I am able to leave the guests without
> very much worries, I also noticed that sometimes the predicted
> swapping occurs, although rarely (I waited about half an hour to catch
> the first swapping on the host). Here is a fragment of vmstat. Note
> that when the first column shows 8-9 - the slowness and huge load
> happens. You can also see how is appears and disappears (with nohz and
> kvm-clock it did not go out of slowness period, but with tsc clock the
> probability of getting out is significantly lower):
>

Are you sure it is hugepages related?

Can you post kvm_stat output while slowness is happening? 'perf top' on 
the host?  and on the guest?

-- 
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