From: Kiryl Shutsemau <kirill@shutemov.name>
To: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Lance Yang <lance.yang@linux.dev>,
Hugh Dickins <hughd@google.com>,
akpm@linux-foundation.org, david@redhat.com, ziy@nvidia.com,
baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com,
npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com,
baohua@kernel.org, ioworker0@gmail.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH mm-new 1/3] mm/khugepaged: skip unsuitable VMAs earlier in khugepaged_scan_mm_slot()
Date: Tue, 16 Sep 2025 10:48:22 +0100 [thread overview]
Message-ID: <3az7vzkhpa2pup3td5pbrek6ti2fij574qimtnbpecums7ixyl@upabkyqmtiaf> (raw)
In-Reply-To: <2466c068-ccd7-41a1-bef7-6f3fefc6ff55@lucifer.local>
On Tue, Sep 16, 2025 at 10:39:53AM +0100, Lorenzo Stoakes wrote:
> On Tue, Sep 16, 2025 at 10:29:11AM +0100, Kiryl Shutsemau wrote:
> > On Tue, Sep 16, 2025 at 02:21:26PM +0800, Lance Yang wrote:
> > > Users of mlock() expect low and predictable latency. THP collapse is a
> > > heavy operation that introduces exactly the kind of unpredictable delays
> > > they want to avoid. It has to unmap PTEs, copy data from the small folios
> > > to a new THP, and then remap the THP back to the PMD ;)
> >
> > Generally, we allow minor page faults into mlocked VMAs and avoid major.
> > This is minor page fault territory in my view.
>
> Hm, but we won't be causing minor faults via reclaim right, since they're
> not on any LRU?
PTEs are still present when we do THP allocation. No reclaim while the
access is blocked. We only block the access on copy and PTEs->PMD
collapse.
--
Kiryl Shutsemau / Kirill A. Shutemov
next prev parent reply other threads:[~2025-09-16 9:48 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-14 14:35 [PATCH mm-new 0/3] mm/khugepaged: optimize collapse candidate detection Lance Yang
2025-09-14 14:35 ` [PATCH mm-new 1/3] mm/khugepaged: skip unsuitable VMAs earlier in khugepaged_scan_mm_slot() Lance Yang
2025-09-14 16:16 ` Dev Jain
2025-09-15 3:02 ` Lance Yang
2025-09-16 5:32 ` Hugh Dickins
2025-09-16 6:21 ` Lance Yang
2025-09-16 6:42 ` Hugh Dickins
2025-09-16 7:05 ` Lance Yang
2025-09-16 9:29 ` Kiryl Shutsemau
2025-09-16 9:39 ` Lorenzo Stoakes
2025-09-16 9:48 ` Kiryl Shutsemau [this message]
2025-09-16 9:58 ` Lorenzo Stoakes
2025-09-16 10:00 ` Lance Yang
2025-09-16 9:59 ` Lance Yang
2025-09-14 14:35 ` [PATCH mm-new 2/3] mm: clean up and expose is_guard_pte_marker() Lance Yang
2025-09-14 16:38 ` Dev Jain
2025-09-15 4:24 ` Lance Yang
2025-09-15 13:54 ` Lorenzo Stoakes
2025-09-15 14:26 ` Lance Yang
2025-09-17 10:32 ` David Hildenbrand
2025-09-14 14:35 ` [PATCH mm-new 3/3] mm/khugepaged: abort collapse scan on guard PTEs Lance Yang
2025-09-14 17:03 ` Dev Jain
2025-09-15 3:36 ` Lance Yang
2025-09-15 14:08 ` Lorenzo Stoakes
2025-09-15 14:42 ` Lance Yang
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