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Re: [RFC PATCH 1/2] xen/unpopulated-alloc: Introduce helpers for DMA allocations
- To: Stefano Stabellini <sstabellini@xxxxxxxxxx>
- From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Date: Thu, 16 Jun 2022 10:49:34 +0200
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- Cc: Oleksandr <olekstysh@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Julien Grall <julien@xxxxxxx>
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On Tue, Jun 14, 2022 at 05:45:53PM -0700, Stefano Stabellini wrote:
> Basically, if we allocate (and free) page-by-page it leads to more
> efficient resource utilization but it is slower. If we allocate larger
> contiguous chunks it is faster but it leads to less efficient resource
> utilization.
>
> Given that on both x86 and ARM the unpopulated memory resource is
> arbitrarily large, I don't think we need to worry about resource
> utilization. It is not backed by real memory. The only limitation is the
> address space size which is very large.
Well, unpopulated memory will consume memory to populate the related
metadata (ie: struct page and realted tracking information) for the
unpopulated region, so it's not completely free.
Thanks, Roger.
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