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Date: Thu, 16 Jun 2022 10:49:34 +0200 From: Roger Pau Monné <roger.pau@...rix.com> To: Stefano Stabellini <sstabellini@...nel.org> Cc: Oleksandr <olekstysh@...il.com>, xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org, Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>, Boris Ostrovsky <boris.ostrovsky@...cle.com>, Juergen Gross <jgross@...e.com>, Julien Grall <julien@....org> Subject: Re: [RFC PATCH 1/2] xen/unpopulated-alloc: Introduce helpers for DMA allocations 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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