Re: Very high memory usage with KVM

[Avi Kivity <avi@redhat.com>]

On 07/26/2009 06:50 PM, Daniel Bareiro wrote:
>> kvm memory management with pre 2.6.27 host kernels is pretty weak.
>> Using a newer host kernel (and newer kvm) may solve this problem.
>>      
>
> Initially I am going to see how it improves the situation upgrading to
> KVM-84 of backports of Hardy Heron, since at the moment last kernel
> available for Hardy is the one I has commented.
>
> I would like to know if the newest versions of KVM published in the
> official site of the project solve a bug recently reported in Ubuntu
> Launchpad [1]. Also I was observing errors of type 'to swapper Not
> tainted' or 'java Not tainted' in the VM (aps2, with a high rate of I/O)
> and that I've commented in a previous message sent to the list [2]. I
> would want to know if you could indicate to me if this can be due to KVM
> bug that would be solved in a later version.
>
>    

My guess is that it is due to poor swapping with pre-2.6.27 hosts. 15 GB 
used out of 16GB total is just 6% reserve, which may be a bit too low.  
With a 2.6.27 host some small amount of memory would be swapped out, 
before that you'd see thrashing.  Another way to check is to drop one 
guest (or reduce total memory needed by 1GB) and see if you get the same 
results or if things improve.

-- 
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