RE: [Xen-devel] OOM problems

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 13.11.10 at 10:13, Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx> wrote:
>>   > What do the guests use for storage? (e.g. "blktap2 for VHD files on
>> an iscsi mounted ext3 volume")
>> 
>> Simple sparse .img files on a local ext4 RAID volume, using "file:".
> 
> 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.

Shouldn't this lead to the calling process being throttled, instead of
the system running into OOM?

Further, having got reports of similar problems lately, too, we have
indications that using pv drivers also gets us around the issue,
which makes me think that it's rather qemu-dm misbehaving (and
not getting stopped doing so by the kernel for whatever reason -
possibly just missing some non-infinite rlimit setting).

Not knowing much about the workings of stubdom, one thing I
don't really understand is how qemu-dm in Dom0 would be
heavily resource consuming here (actually I would have expected
no qemu-dm in Dom0 at all in this case). Aren't the main I/O paths
going from qemu-stubdom directly to the backends?

Jan


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