linux-kernel - Re: [RFC PATCH 3/3] mm/map_contig: Add mmap(MAP

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Message-ID: <704611ff-2fb0-9b99-6edb-b050e3d1e850@suse.cz>
Date:   Tue, 17 Oct 2017 08:59:41 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Mike Kravetz <mike.kravetz@...cle.com>,
        Michal Hocko <mhocko@...nel.org>
Cc:     Guy Shattah <sguy@...lanox.com>,
        Christopher Lameter <cl@...ux.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Michal Nazarewicz <mina86@...a86.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        Laura Abbott <labbott@...hat.com>
Subject: Re: [RFC PATCH 3/3] mm/map_contig: Add mmap(MAP_CONTIG) support

On 10/16/2017 10:32 PM, Mike Kravetz wrote:
> Agree.  I only wanted to point out the similarities.
> But, it does make me wonder how much of a benefit hugetlb 1G pages would
> make in the the RDMA performance comparison.  The table in the presentation
> show a average speedup of something like 27% (or so) for contiguous allocation
> which I assume are 2GB in size.  Certainly, using hugetlb is not the ideal
> case, just wondering if it does help and how much.

Good point. If somebody cares about performance benefits of contiguous
memory wrt device access, they would probably want also the TLB
performance benefits of huge pages.