Re: [Xen-devel] [RFC PATCH] page_alloc: use first half of higher order chunks when halving

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.04.14 at 23:32, <tim@xxxxxxx> wrote:
>  (c) If for some reason the current hypercall API is not sufficient
>      for dom0 to get what it wants, we should consider adding some new
>      operation/flag/mode somewhere.  But since AFAIK there's already
>      another path in linux that allocates contiguous DMA buffers
>      for device drivers, presumably this isn't the case.

And it should be kept in mind that requesting contiguous memory
shouldn't be done at will, as it may end up exhausting the portion
of memory intended for DMA-style allocations (SWIOTLB / DMA-
coherent allocations in Linux). I.e. neither Dom0 nor DomU should
be trying to populate large parts of their memory with contiguous
allocation requests to the hypervisor. They may, if they so desire,
go and re-arrange their P2M mapping (solely based on what they
got handed by doing order-0 allocations).

Jan


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