linux-kernel - Re: [RFC] mmap(MAP

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Message-ID: <xa1tk20bxh5u.fsf@mina86.com>
Date:   Wed, 04 Oct 2017 13:54:05 +0200
From:   Michal Nazarewicz <mina86@...a86.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Guy Shattah <sguy@...lanox.com>,
        Christoph Lameter <cl@...ux.com>,
        Mike Kravetz <mike.kravetz@...cle.com>
Subject: Re: [RFC] mmap(MAP_CONTIG)

On Tue, Oct 03 2017, Mike Kravetz wrote:
> At Plumbers this year, Guy Shattah and Christoph Lameter gave a presentation
> titled 'User space contiguous memory allocation for DMA' [1].  The slides
> point out the performance benefits of devices that can take advantage of
> larger physically contiguous areas.

Issue I have is that kind of memory needed may depend on a device.  Some
may require contiguous blocks.  Some may support scatter-gather.  Some
may be behind IO-MMU and not care either way.

Furthermore, I feel déjà vu.  Wasn’t dmabuf supposed to address this
issue?

-- 
Best regards
ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ
«If at first you don’t succeed, give up skydiving»