[Xen-devel] RE: TODO in windows balloon driver

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> 
> HI James:
> 
>       I've noticed the TODO tag in xenpci/xenpci_fdo.c, line 294
> 
>    290         KdPrint((__DRIVER_NAME "     Calling
> HYPERVISOR_memory_op(XENMEM_populate_physmap) - pfn_count = %d\n",
> pfn_count));
>    291         ret = HYPERVISOR_memory_op(xpdd,
XENMEM_populate_physmap,
> &reservation);
>    292         ExFreePoolWithTag(pfns, XENPCI_POOL_TAG);
>    293         KdPrint((__DRIVER_NAME "     populated %d pages\n",
ret));
>    294         /* TODO: what do we do if less than the required number
of
> pages were populated??? can this happen??? */
> 
> 
>       Could we fix it in linux balloon driver way?
>       When no enough pfn_count got, give memory back to xen.
>       What do you think?
>       Thanks.

I guess that would work, but then it would keep trying to decrease again
every second. Maybe that's what we want but I'd rather put in some sort
of backoff in there eg retry in one second then two seconds then 4
seconds etc up to a maximum of 1 minute or so, to reduce the noise.

Are you seeing this happen? I'm guessing it's because xen doesn't have
enough pages for you or because you've ballooned up above the maxmem
limit or something...

James


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