From: Rik van Riel <riel@surriel.com>
To: "David Hildenbrand (Arm)" <david@kernel.org>,
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 0/12] mm: use per-VMA lock in __access_remote_vm for improved monitoring reliability
Date: Fri, 11 Sep 2026 12:03:45 -0400 [thread overview]
Message-ID: <7c7b028ae93f0551e07e9e09468954e76ad072ee.camel@surriel.com> (raw)
In-Reply-To: <9e902c8e-c825-45ee-89a1-85923453e43d@kernel.org>
On Fri, 2026-09-11 at 17:11 +0200, David Hildenbrand (Arm) wrote:
> On 7/25/26 00:29, Rik van Riel wrote:
> > __access_remote_vm() holds mmap_read_lock() for the whole transfer.
> > On
> > large machines, with large multi-threaded applications, the
> > mmap_lock
> > is often contended, leading to things like reads of
> > /proc/PID/cmdline
> > stalling.
> >
> > This results in system monitoring tools getting stuck, right when
> > system information would be the most helpful.
>
> Rik, what's the status of this, and which series do you consider more
> relevant:
> the pure per-VMA lock change or the pure page-table walking + folio
> batching?
>
> I'd assume the page-table walking would result in more speedup and
> the per-VMA
> in mostly less contention. So likely we'd want the page-table walking
> optimization first.
We can merge them in either order.
This series gives a speedup as well, by removing
the double VMA lookup.
If you want to merge the page table walking and
folio batching change first, I can easily rebase
this per-VMA lock series on top of that.
Do you have additional feedback on changes you
want me to make to get the page table walking
and folio batching thing in a merge-ready shape?
--
All Rights Reversed.
next prev parent reply other threads:[~2026-09-11 16:04 UTC|newest]
Thread overview: 36+ 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)
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)
2026-09-11 15:11 ` [PATCH RFC v4 0/12] mm: use per-VMA lock in __access_remote_vm for improved monitoring reliability David Hildenbrand (Arm)
2026-09-11 16:03 ` Rik van Riel [this message]
2026-09-11 16:44 ` David Hildenbrand (Arm)
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