Re: [Xen-devel] Assigning contiguous memory to a driver domain

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 15.09.10 at 16:44, Rafal Wojtczuk <rafal@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> On Wed, Sep 15, 2010 at 02:49:37PM +0100, Jan Beulich wrote:
>> Because on suspend the driver frees the memory which on resume
>> it will allocate back?
> I am a bit lost.
> By "frees the memory" you mean "return contiguous memory to Xen free memory" 
> ?
> Does it really work this way ?

Yes - the "special" memory gets exchanged back to "normal" memory
upon freeing of it by the driver. The exception is if Xen has no "normal"
memory left to give back out in exchange - in that case the domain will
retain the "special" memory indefinitely. Yes, you can call this a leak,
but no, I don't think there's much you can do about it (without adding
likely rather complex extra code).

> If so, it requires nonzero Xen free memory ? And that is why when I do
> "ifconfig eth0 down; ifconfig eth0 up" in the driver domain the second one
> fails ?

Generally the second "up" shouldn't fail as long as the prior "down"
properly returned all resources. See the restrictions above.

Jan


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