From: Alistair Popple <apopple@nvidia.com>
To: Felix Kuehling <felix.kuehling@amd.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>,
David Hildenbrand <david@redhat.com>,
Christoph Hellwig <hch@lst.de>, Alex Sierra <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, jglisse@redhat.com,
willy@infradead.org
Subject: Re: [PATCH v6 01/10] mm: add zone device coherent type memory support
Date: Fri, 18 Feb 2022 11:59:37 +1100 [thread overview]
Message-ID: <87y229askb.fsf@nvdebian.thelocal> (raw)
In-Reply-To: <bf16195e-2570-3687-2b53-3f597ebfcfec@amd.com>
[-- Attachment #1: Type: text/plain, Size: 1949 bytes --]
Felix Kuehling <felix.kuehling@amd.com> writes:
> Am 2022-02-16 um 07:26 schrieb Jason Gunthorpe:
>> The other place that needs careful audit is all the callers using
>> vm_normal_page() - they must all be able to accept a ZONE_DEVICE page
>> if we don't set pte_devmap.
>
> How much code are we talking about here? A quick search finds 26 call-sites in
> 12 files in current master:
>
> fs/proc/task_mmu.c
> mm/hmm.c
> mm/gup.c
> mm/huge_memory.c (vm_normal_page_pmd)
> mm/khugepaged.c
> mm/madvise.c
> mm/mempolicy.c
> mm/memory.c
> mm/mlock.c
> mm/migrate.c
> mm/mprotect.c
> mm/memcontrol.c
>
> I'm thinking of a more theoretical approach: Instead of auditing all users, I'd
> ask, what are the invariants that a vm_normal_page should have. Then check,
> whether our DEVICE_COHERENT pages satisfy them. But maybe the concept of a
> vm_normal_page isn't defined clearly enough for that.
>
> That said, I think we (Alex and myself) made an implicit assumption from the
> start, that a DEVICE_COHERENT page should behave a lot like a normal page in
> terms of VMA mappings, even if we didn't know what that means in detail.
Yes I'm afraid I made a similar mistake when reviewing this, forgetting that
DEVICE_COHERENT pages are not LRU pages and therefore need special treatment in
some places. So for now I will have to withdraw my reviewed-by until this has
been looked at more closely, because as you note below accidentally treating
them as LRU pages leads to a bad time.
> I can now at least name some differences between DEVICE_COHERENT and normal
> pages: how the memory is allocated, how data is migrated into DEVICE_COHERENT
> pages and that it can't be on any LRU list (because the lru list_head in struct
> page is aliased by pgmap and zone_device_data). Maybe I'll find more differences
> if I keep digging.
>
> Regards,
> Felix
>
>
>>
>> Jason
next prev parent reply other threads:[~2022-02-18 1:10 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-01 15:48 [PATCH v6 00/10] Add MEMORY_DEVICE_COHERENT for coherent device memory mapping Alex Sierra
2022-02-01 15:48 ` [PATCH v6 01/10] mm: add zone device coherent type memory support Alex Sierra
2022-02-11 16:15 ` David Hildenbrand
2022-02-11 16:39 ` David Hildenbrand
2022-02-11 16:52 ` Sierra Guiza, Alejandro (Alex)
2022-02-11 17:07 ` Felix Kuehling
2022-02-15 12:16 ` David Hildenbrand
2022-02-15 14:45 ` Jason Gunthorpe
2022-02-15 18:32 ` Christoph Hellwig
2022-02-15 19:41 ` Jason Gunthorpe
2022-02-15 21:35 ` Felix Kuehling
2022-02-15 21:47 ` Jason Gunthorpe
2022-02-15 22:49 ` Felix Kuehling
2022-02-16 2:01 ` Jason Gunthorpe
2022-02-16 16:56 ` Felix Kuehling
2022-02-16 17:28 ` Jason Gunthorpe
2022-02-16 1:23 ` Alistair Popple
2022-02-16 2:03 ` Jason Gunthorpe
2022-02-16 2:36 ` Alistair Popple
2022-02-16 8:31 ` David Hildenbrand
2022-02-16 12:26 ` Jason Gunthorpe
2022-02-17 1:05 ` Alistair Popple
2022-02-17 21:12 ` Felix Kuehling
2022-02-18 0:19 ` Jason Gunthorpe
2022-02-18 19:20 ` Felix Kuehling
2022-02-18 19:26 ` Jason Gunthorpe
2022-02-18 19:37 ` Felix Kuehling
2022-02-28 20:34 ` [PATCH] mm: split vm_normal_pages for LRU and non-LRU handling Alex Sierra
2022-02-28 22:41 ` Felix Kuehling
2022-03-01 8:03 ` David Hildenbrand
2022-03-01 16:08 ` Felix Kuehling
2022-03-01 16:22 ` David Hildenbrand
2022-03-01 16:30 ` Felix Kuehling
2022-03-01 16:32 ` David Hildenbrand
2022-02-18 0:59 ` Alistair Popple [this message]
2022-02-11 16:45 ` [PATCH v6 01/10] mm: add zone device coherent type memory support Jason Gunthorpe
2022-02-11 16:49 ` David Hildenbrand
2022-02-11 16:56 ` Jason Gunthorpe
2022-02-15 12:15 ` David Hildenbrand
2022-02-15 18:52 ` Felix Kuehling
2022-02-11 17:05 ` Felix Kuehling
2022-02-14 2:04 ` Alistair Popple
2022-02-01 15:48 ` [PATCH v6 02/10] mm: add device coherent vma selection for memory migration Alex Sierra
2022-02-01 15:48 ` [PATCH v6 03/10] mm/gup: fail get_user_pages for LONGTERM dev coherent type Alex Sierra
2022-02-01 15:48 ` [PATCH v6 04/10] drm/amdkfd: add SPM support for SVM Alex Sierra
2022-02-01 15:48 ` [PATCH v6 05/10] drm/amdkfd: coherent type as sys mem on migration to ram Alex Sierra
2022-02-01 15:48 ` [PATCH v6 06/10] lib: test_hmm add ioctl to get zone device type Alex Sierra
2022-02-01 15:48 ` [PATCH v6 07/10] lib: test_hmm add module param for " Alex Sierra
2022-02-01 15:48 ` [PATCH v6 08/10] lib: add support for device coherent type in test_hmm Alex Sierra
2022-02-01 15:49 ` [PATCH v6 09/10] tools: update hmm-test to support device coherent type Alex Sierra
2022-02-01 15:49 ` [PATCH v6 10/10] tools: update test_hmm script to support SP config Alex Sierra
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87y229askb.fsf@nvdebian.thelocal \
--to=apopple@nvidia.com \
--cc=akpm@linux-foundation.org \
--cc=alex.sierra@amd.com \
--cc=amd-gfx@lists.freedesktop.org \
--cc=david@redhat.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=felix.kuehling@amd.com \
--cc=hch@lst.de \
--cc=jgg@nvidia.com \
--cc=jglisse@redhat.com \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-xfs@vger.kernel.org \
--cc=rcampbell@nvidia.com \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).