From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Rik van Riel <riel@surriel.com>,
Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
kernel-team@meta.com, Dave Hansen <dave.hansen@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Suren Baghdasaryan <surenb@google.com>,
Lorenzo Stoakes <ljs@kernel.org>,
Vlastimil Babka <vbabka@kernel.org>,
"Liam R. Howlett" <liam@infradead.org>,
Mike Rapoport <rppt@kernel.org>, Michal Hocko <mhocko@suse.com>,
Jason Gunthorpe <jgg@ziepe.ca>,
John Hubbard <jhubbard@nvidia.com>, Peter Xu <peterx@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
Usama Arif <usamaarif642@gmail.com>
Subject: Re: [PATCH RFC v4 11/12] mm/gup: batch contiguous PTE-mapped large folios in follow_page_mask()
Date: Tue, 28 Jul 2026 21:05:42 +0200 [thread overview]
Message-ID: <7fbdb447-3d6c-4071-bc6d-1af4e44cbd7f@kernel.org> (raw)
In-Reply-To: <a086dbb3cc9ee8faa638c70bd282ca31c58d402d.camel@surriel.com>
On 7/28/26 02:37, Rik van Riel wrote:
> On Mon, 2026-07-27 at 15:54 +0200, David Hildenbrand (Arm) wrote:
>> On 7/25/26 00:29, Rik van Riel wrote:
>>>
>>> gup_test -L -m 256 -n 65536 -r 16 -t
>>> before after
>>> 64 kB mTHP 3140 us 412 us (7.6x)
>>> 2 MB THP (control) 78 us 76 us
>>> 4 kB base (control) 3010 us 3042 us
>>>
>>> The PMD-mapped 2 MB THP already returns the whole mapping in one
>>> step, so
>>> it stays fast and unchanged. The 4 kB baseline shows the per-page
>>> walk cost
>>> that the 64 kB case paid before this change; only the PTE-mapped
>>> large
>>> folio case improves.
>>>
>>> Assisted-by: Claude:claude-opus-4.8
>>> Signed-off-by: Rik van Riel <riel@surriel.com>
>>
>> Why is this patch part of this patch set?
>>
>> This makes perfect sense independently, no?
>
> I'm happy to drop this for now. I think it would
> fit in better with another optimization to only
> take one refcount per continuously mapped extent
> of pages from the same folio.
>
> I can't really untangle it because it modifies
> some of the same code as other patches in the
> series, but I'm happy to save it for a follow-up.
Given this series here is RFC, can't we have that optimization upfront? I'd
assume it will benefit quite some use cases that pin multiple consecutive pages.
IIUC, it'd be mostly patch 10+11. No need to worry about the test case right
now, we can do that later.
--
Cheers,
David
next prev parent reply other threads:[~2026-07-28 19:05 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-24 22:29 [PATCH RFC v4 0/12] mm: use per-VMA lock in __access_remote_vm for improved monitoring reliability Rik van Riel
2026-07-24 22:29 ` [PATCH RFC v4 01/12] x86/mm: add untagged_addr_remote_unlocked() Rik van Riel
2026-07-27 14:50 ` Suren Baghdasaryan
2026-07-28 1:39 ` John Hubbard
2026-07-24 22:29 ` [PATCH RFC v4 02/12] riscv/mm: " Rik van Riel
2026-07-27 14:53 ` Suren Baghdasaryan
2026-07-28 1:44 ` John Hubbard
2026-07-24 22:29 ` [PATCH RFC v4 03/12] mm: rename get_user_page_vma_remote() to get_user_page_lookup_vma() Rik van Riel
2026-07-27 14:58 ` Suren Baghdasaryan
2026-07-24 22:29 ` [PATCH RFC v4 04/12] mm/gup: let check_vma_flags() ignore selected VMA flags Rik van Riel
2026-07-27 15:03 ` Suren Baghdasaryan
2026-07-28 2:40 ` John Hubbard
2026-07-28 14:29 ` Rik van Riel
2026-07-24 22:29 ` [PATCH RFC v4 05/12] mm/gup: add get_user_page_vma() to fault in a page under a held lock Rik van Riel
2026-07-27 16:54 ` Suren Baghdasaryan
2026-07-28 2:45 ` John Hubbard
2026-07-24 22:29 ` [PATCH RFC v4 06/12] mm: use per-VMA lock in __access_remote_vm() for single-VMA accesses Rik van Riel
2026-07-27 18:51 ` Suren Baghdasaryan
2026-07-24 22:29 ` [PATCH RFC v4 07/12] mm: read remote strings under the per-VMA lock Rik van Riel
2026-07-24 22:29 ` [PATCH RFC v4 08/12] selftests/mm: cover /proc/pid/mem access to VM_PFNMAP memory Rik van Riel
2026-07-28 20:58 ` John Hubbard
2026-07-24 22:29 ` [PATCH RFC v4 09/12] mm/gup: build get_user_page_lookup_vma() on get_user_page_vma() Rik van Riel
2026-07-24 22:29 ` [PATCH RFC v4 10/12] mm/gup: pass an end address to follow_page_mask() and return a page count Rik van Riel
2026-07-24 22:29 ` [PATCH RFC v4 11/12] mm/gup: batch contiguous PTE-mapped large folios in follow_page_mask() Rik van Riel
2026-07-27 13:54 ` David Hildenbrand (Arm)
2026-07-28 0:37 ` Rik van Riel
2026-07-28 19:05 ` David Hildenbrand (Arm) [this message]
2026-07-28 20:49 ` Rik van Riel
2026-07-24 22:29 ` [PATCH RFC v4 12/12] selftests/mm: add a slow-GUP content and COW test for mTHP Rik van Riel
2026-07-26 11:56 ` Mike Rapoport
2026-07-27 14:05 ` David Hildenbrand (Arm)
2026-07-28 20:31 ` Rik van Riel
2026-07-27 13:53 ` David Hildenbrand (Arm)
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