linux-kernel - Re: [v1 resend 00/12] THP support for zone device page migration

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Message-ID: <6ac61b0b-980a-487e-8b88-8ff1bc3f9f17@redhat.com>
Date: Tue, 8 Jul 2025 16:53:03 +0200
From: David Hildenbrand <david@...hat.com>
To: Balbir Singh <balbirs@...dia.com>, linux-mm@...ck.org
Cc: akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
 Karol Herbst <kherbst@...hat.com>, Lyude Paul <lyude@...hat.com>,
 Danilo Krummrich <dakr@...nel.org>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Jérôme Glisse
 <jglisse@...hat.com>, Shuah Khan <shuah@...nel.org>,
 Barry Song <baohua@...nel.org>, Baolin Wang <baolin.wang@...ux.alibaba.com>,
 Ryan Roberts <ryan.roberts@....com>, Matthew Wilcox <willy@...radead.org>,
 Peter Xu <peterx@...hat.com>, Zi Yan <ziy@...dia.com>,
 Kefeng Wang <wangkefeng.wang@...wei.com>, Jane Chu <jane.chu@...cle.com>,
 Alistair Popple <apopple@...dia.com>, Donet Tom <donettom@...ux.ibm.com>
Subject: Re: [v1 resend 00/12] THP support for zone device page migration

On 04.07.25 01:34, Balbir Singh wrote:

So, I shared some feedback as reply to "[RFC 00/11] THP support for zone 
device pages".

It popped up in my mail box again after there apparently was a 
discussion a couple of days ago.

... and now I realize that this is apparently the same series with 
renamed subject. Gah.

So please, find my feedback there -- most of that should still apply, 
scanning your changelog ...


> Changelog v1:
> - Changes from RFC [2], include support for handling fault_folio and using
>    trylock in the fault path
> - A new test case has been added to measure the throughput improvement
> - General refactoring of code to keep up with the changes in mm
> - New split folio callback when the entire split is complete/done. The
>    callback is used to know when the head order needs to be reset.
> 
> Testing:
> - Testing was done with ZONE_DEVICE private pages on an x86 VM
> - Throughput showed upto 5x improvement with THP migration, system to device
>    migration is slower due to the mirroring of data (see buffer->mirror)
> 
> 
> Balbir Singh (12):
>    mm/zone_device: support large zone device private folios
>    mm/migrate_device: flags for selecting device private THP pages
>    mm/thp: zone_device awareness in THP handling code
>    mm/migrate_device: THP migration of zone device pages
>    mm/memory/fault: add support for zone device THP fault handling
>    lib/test_hmm: test cases and support for zone device private THP
>    mm/memremap: add folio_split support
>    mm/thp: add split during migration support
>    lib/test_hmm: add test case for split pages
>    selftests/mm/hmm-tests: new tests for zone device THP migration
>    gpu/drm/nouveau: add THP migration support
>    selftests/mm/hmm-tests: new throughput tests including THP
> 
>   drivers/gpu/drm/nouveau/nouveau_dmem.c | 246 +++++++---
>   drivers/gpu/drm/nouveau/nouveau_svm.c  |   6 +-
>   drivers/gpu/drm/nouveau/nouveau_svm.h  |   3 +-
>   include/linux/huge_mm.h                |  18 +-
>   include/linux/memremap.h               |  29 +-
>   include/linux/migrate.h                |   2 +
>   include/linux/mm.h                     |   1 +
>   lib/test_hmm.c                         | 428 +++++++++++++----
>   lib/test_hmm_uapi.h                    |   3 +
>   mm/huge_memory.c                       | 261 ++++++++---
>   mm/memory.c                            |   6 +-
>   mm/memremap.c                          |  50 +-
>   mm/migrate.c                           |   2 +
>   mm/migrate_device.c                    | 488 +++++++++++++++++---
>   mm/page_alloc.c                        |   1 +
>   mm/page_vma_mapped.c                   |  10 +
>   mm/pgtable-generic.c                   |   6 +
>   mm/rmap.c                              |  19 +-
>   tools/testing/selftests/mm/hmm-tests.c | 607 ++++++++++++++++++++++++-
>   19 files changed, 1874 insertions(+), 312 deletions(-)
> 


-- 
Cheers,

David / dhildenb