Re: [Xen-devel] OOM problems

[Daniel Stodden <daniel.stodden@xxxxxxxxxx>]

On Sat, 2010-11-13 at 05:19 -0500, John Weekes wrote:
> On 11/13/2010 1:13 AM, Ian Pratt wrote:
>  > Ah, if you're using loop it may be that you're just filling memory 
> with dirty pages. Older kernels certainly did this, not sure about newer 
> ones.
>  > I'd be inclined to use blktap2 in raw file mode, with "aio:".
> 
> With blktap2, is free RAM in dom0 still used for a disk cache at all? I 
> have this dom0 set to 1.5 GB mainly to help with caching; if that RAM is 
> not needed, I'll retool it down to a smaller number.

If you're not using cloned images deriving from a shared parent image,
that caching won't buy anyone much. Memory better spent on the guests
themselves then, thereby their own caches. 

Keep an eye on /proc/meminfo, it largely depends on number/type of
guests, but probably safe to reassign ~800M straight away.

blktap2 with aio will move the datapath to direct I/O. Comparend to
buffered loops, there's also some notable benefit to crash consistency
resulting from that.

Daniel


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