From: Kiryl Shutsemau <kirill@shutemov.name>
To: Gladyshev Ilya <gladyshev.ilya1@h-partners.com>
Cc: guohanjun@huawei.com, wangkefeng.wang@huawei.com,
weiyongjun1@huawei.com, yusongping@huawei.com,
leijitang@huawei.com, artem.kuzin@huawei.com,
stepanov.anatoly@huawei.com, alexander.grubnikov@huawei.com,
gorbunov.ivan@h-partners.com, akpm@linux-foundation.org,
david@kernel.org, lorenzo.stoakes@oracle.com,
Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org,
surenb@google.com, mhocko@suse.com, ziy@nvidia.com,
harry.yoo@oracle.com, willy@infradead.org, yuzhao@google.com,
baolin.wang@linux.alibaba.com, muchun.song@linux.dev,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 0/2] mm: improve folio refcount scalability
Date: Mon, 12 Jan 2026 16:17:49 +0000 [thread overview]
Message-ID: <aWUdHYjHPQGpF-92@thinkstation> (raw)
In-Reply-To: <d9fe0fb8-2c83-4eeb-8513-853522909253@h-partners.com>
On Mon, Jan 12, 2026 at 05:32:10PM +0300, Gladyshev Ilya wrote:
> On 1/12/2026 2:49 PM, Kiryl Shutsemau wrote:
> > On Mon, Jan 12, 2026 at 11:30:38AM +0300, Gladyshev Ilya wrote:
> > > Gentle ping on this proposal
> >
> > I generally like the idea, but I would like to hear from folks who
> > actually understand serialization.
> >
> > Also, do you have number for "a full CAS loop when the counter is
> > approaching overflow" thing?
> >
> I am not sure that overflow is a real problem because you need a very
> specific race condition over a long time to achieve it...
Yes. But if the page is popular for pinning, GUP_PIN_COUNTING_BIAS can
cut the "very long time" substantially.
> But as a safeguard, everything lower than 2^31 - #max concurrent
> accesses (~#num cpu) should work, so let's say 2^30
What I meant is when we put a branch/loop in the hot path, your
performance numbers will likely not look as attractive. Am I wrong?
--
Kiryl Shutsemau / Kirill A. Shutemov
next prev parent reply other threads:[~2026-01-12 16:18 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-19 12:46 [RFC PATCH 0/2] mm: improve folio refcount scalability Gladyshev Ilya
2025-12-19 12:46 ` [RFC PATCH 1/2] mm: make ref_unless functions unless_zero only Gladyshev Ilya
2026-02-06 13:16 ` David Hildenbrand (Arm)
2025-12-19 12:46 ` [RFC PATCH 2/2] mm: implement page refcount locking via dedicated bit Gladyshev Ilya
2025-12-19 14:50 ` Kiryl Shutsemau
2025-12-19 16:18 ` Gladyshev Ilya
2025-12-19 17:46 ` Kiryl Shutsemau
2025-12-19 19:08 ` Gladyshev Ilya
2025-12-22 13:33 ` Kiryl Shutsemau
2025-12-19 18:17 ` Gregory Price
2025-12-22 12:42 ` Gladyshev Ilya
2025-12-22 23:36 ` kernel test robot
2026-01-12 8:30 ` [RFC PATCH 0/2] mm: improve folio refcount scalability Gladyshev Ilya
2026-01-12 11:49 ` Kiryl Shutsemau
2026-01-12 14:32 ` Gladyshev Ilya
2026-01-12 16:17 ` Kiryl Shutsemau [this message]
2026-01-13 7:31 ` Gladyshev Ilya
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