From: Christoph Hellwig <hch@lst.de>
To: Felix Kuehling <felix.kuehling@amd.com>
Cc: Christoph Hellwig <hch@lst.de>,
"Sierra Guiza, Alejandro (Alex)" <alex.sierra@amd.com>,
akpm@linux-foundation.org, linux-mm@kvack.org,
rcampbell@nvidia.com, linux-ext4@vger.kernel.org,
linux-xfs@vger.kernel.org, amd-gfx@lists.freedesktop.org,
dri-devel@lists.freedesktop.org, jgg@nvidia.com,
jglisse@redhat.com
Subject: Re: [PATCH v1 03/14] mm: add iomem vma selection for memory migration
Date: Wed, 1 Sep 2021 10:29:25 +0200 [thread overview]
Message-ID: <20210901082925.GA21961@lst.de> (raw)
In-Reply-To: <e40b3b79-f548-b87b-7a85-f654f25ed8dd@amd.com>
On Mon, Aug 30, 2021 at 01:04:43PM -0400, Felix Kuehling wrote:
> >> driver code is not really involved in updating the CPU mappings. Maybe
> >> it's something we need to do in the migration helpers.
> > It looks like I'm totally misunderstanding what you are adding here
> > then. Why do we need any special treatment at all for memory that
> > has normal struct pages and is part of the direct kernel map?
>
> The pages are like normal memory for purposes of mapping them in CPU
> page tables and for coherent access from the CPU.
That's the user page tables. What about the kernel direct map?
If there is a normal kernel struct page backing there really should
be no need for the pgmap.
> From an application
> perspective, we want file-backed and anonymous mappings to be able to
> use DEVICE_PUBLIC pages with coherent CPU access. The goal is to
> optimize performance for GPU heavy workloads while minimizing the need
> to migrate data back-and-forth between system memory and device memory.
I don't really understand that part. file backed pages are always
allocated by the file system using the pagecache helpers, that is
using the page allocator. Anonymouns memory also always comes from
the page allocator.
> The pages are special in two ways:
>
> 1. The memory is managed not by the Linux buddy allocator, but by the
> GPU driver's TTM memory manager
Why?
> 2. We want to migrate data in response to GPU page faults and
> application hints using the migrate_vma helpers
Why?
next prev parent reply other threads:[~2021-09-01 8:29 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-25 3:48 [PATCH v1 00/14] Add MEMORY_DEVICE_PUBLIC for CPU-accessible coherent device memory Alex Sierra
2021-08-25 3:48 ` [PATCH v1 01/14] ext4/xfs: add page refcount helper Alex Sierra
2021-08-25 7:35 ` Christoph Hellwig
2021-08-25 15:09 ` Theodore Ts'o
2021-08-25 15:49 ` Darrick J. Wong
2021-08-25 3:48 ` [PATCH v1 02/14] mm: remove extra ZONE_DEVICE struct page refcount Alex Sierra
2021-08-25 7:35 ` Christoph Hellwig
2021-08-25 11:15 ` Vlastimil Babka
2021-08-25 17:49 ` Ralph Campbell
2021-08-27 11:26 ` Vlastimil Babka
2021-08-25 3:48 ` [PATCH v1 03/14] mm: add iomem vma selection for memory migration Alex Sierra
2021-08-25 7:40 ` Christoph Hellwig
2021-08-25 7:46 ` Christoph Hellwig
2021-08-25 18:24 ` Sierra Guiza, Alejandro (Alex)
2021-08-26 22:27 ` Felix Kuehling
2021-08-30 8:28 ` Christoph Hellwig
2021-08-30 17:04 ` Felix Kuehling
2021-09-01 8:29 ` Christoph Hellwig [this message]
2021-09-01 15:40 ` Felix Kuehling
2021-09-01 22:03 ` Dave Chinner
2021-09-01 23:07 ` Felix Kuehling
2021-09-02 1:14 ` Dave Chinner
2021-09-09 4:55 ` Felix Kuehling
2021-09-02 8:18 ` Christoph Hellwig
2021-09-02 18:07 ` Dan Williams
2021-09-09 4:02 ` Felix Kuehling
2021-08-25 14:24 ` Felix Kuehling
2021-08-25 3:48 ` [PATCH v1 04/14] mm: add zone device public type memory support Alex Sierra
2021-08-25 3:48 ` [PATCH v1 05/14] drm/amdkfd: ref count init for device pages Alex Sierra
2021-08-25 14:34 ` Felix Kuehling
2021-08-25 3:48 ` [PATCH v1 06/14] drm/amdkfd: add SPM support for SVM Alex Sierra
2021-08-25 14:45 ` Felix Kuehling
2021-08-25 3:48 ` [PATCH v1 07/14] drm/amdkfd: public type as sys mem on migration to ram Alex Sierra
2021-08-25 3:48 ` [PATCH v1 08/14] mm: add public type support to migrate_vma helpers Alex Sierra
2021-08-25 7:47 ` Christoph Hellwig
2021-08-25 3:48 ` [PATCH v1 09/14] mm: call pgmap->ops->page_free for DEVICE_PUBLIC pages Alex Sierra
2021-08-25 7:46 ` Christoph Hellwig
2021-08-25 3:48 ` [PATCH v1 10/14] lib: test_hmm add ioctl to get zone device type Alex Sierra
2021-08-25 3:48 ` [PATCH v1 11/14] lib: test_hmm add module param for " Alex Sierra
2021-08-25 3:48 ` [PATCH v1 12/14] lib: add support for device public type in test_hmm Alex Sierra
2021-08-25 3:48 ` [PATCH v1 13/14] tools: update hmm-test to support device public type Alex Sierra
2021-08-25 3:48 ` [PATCH v1 14/14] tools: update test_hmm script to support SP config Alex Sierra
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