Re: [PATCH 4/5] hmm: heterogeneous memory management v6

From: Rik van Riel
Date: Fri Nov 07 2014 - 16:36:56 EST


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On 11/03/2014 03:42 PM, j.glisse@xxxxxxxxx wrote:
> From: JÃrÃme Glisse <jglisse@xxxxxxxxxx>
>
> Motivation:
>
> Heterogeneous memory management is intended to allow a device to
> transparently access a process address space without having to lock
> pages of the process or take references on them. In other word
> mirroring a process address space while allowing the regular memory
> management event such as page reclamation or page migration, to
> happen seamlessly.
>
> Recent years have seen a surge into the number of specialized
> devices that are part of a computer platform (from desktop to
> phone). So far each of those devices have operated on there own
> private address space that is not link or expose to the process
> address space that is using them. This separation often leads to
> multiple memory copy happening between the device owned memory and
> the process memory. This of course is both a waste of cpu cycle and
> memory.
>
> Over the last few years most of those devices have gained a full
> mmu allowing them to support multiple page table, page fault and
> other features that are found inside cpu mmu. There is now a strong
> incentive to start leveraging capabilities of such devices and to
> start sharing process address to avoid any unnecessary memory copy
> as well as simplifying the programming model of those devices by
> sharing an unique and common address space with the process that
> use them.
>
> The aim of the heterogeneous memory management is to provide a
> common API that can be use by any such devices in order to mirror
> process address. The hmm code provide an unique entry point and
> interface itself with the core mm code of the linux kernel avoiding
> duplicate implementation and shielding device driver code from core
> mm code.

Acked-by: Rik van Riel <riel@xxxxxxxxxx>

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