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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1wFyjP-0000000DrUt-3u9E; Thu, 23 Apr 2026 18:24:56 +0000 Date: Thu, 23 Apr 2026 19:24:55 +0100 From: Matthew Wilcox To: Gorbunov Ivan Cc: david@kernel.org, Liam.Howlett@oracle.com, akpm@linux-foundation.org, apopple@nvidia.com, baolin.wang@linux.alibaba.com, gladyshev.ilya1@h-partners.com, harry.yoo@oracle.com, kirill@shutemov.name, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, mhocko@suse.com, muchun.song@linux.dev, rppt@kernel.org, surenb@google.com, torvalds@linuxfoundation.org, vbabka@suse.cz, yuzhao@google.com, ziy@nvidia.com, artem.kuzin@huawei.com Subject: Re: [PATCH v2 2/2] mm: implement page refcount locking via dedicated bit Message-ID: References: <9936cc799ac8b637ee58ae3bf6ec0e5eeb5306e9.1776350895.git.gorbunov.ivan@h-partners.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9936cc799ac8b637ee58ae3bf6ec0e5eeb5306e9.1776350895.git.gorbunov.ivan@h-partners.com> X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 23D43140002 X-Stat-Signature: dstfhyac81ju5g6s5gr55rswy4bbqgrh X-Rspam-User: X-HE-Tag: 1776968709-588358 X-HE-Meta: U2FsdGVkX1/jpM/giZxbtf47/Z/jOX0cug8AgUboe87f3c2K9uZj8zCKLB+zfwT7iI2ZPkrh8hTCGAlMBw1oySowPV4IoC0kkJmdbq9l3U67DVg7eOePKINvR8fvwnrLTlK8H3S9W4K2Y0YK8ZKGzC4diZLedUebtsxtrQ0c1YdAgUoo6TDmzTUg+OVaM45YPGihsFyjEP7wLyE8W9jCjz+h/cAm6Rdo0C4hiooj81m/t+aWSCljb8qWR4mQSJCS2Xxz4mMtnwO+StWSc3YQsnY/szu8t3aIfcxlnbIwso73jB6p9va+to/VdRaUnoBfKfu8IKna5DuUKUCgGU+qApA44ooEmmslRIBcfb3fZKZVpMiRglT9J5A79S21+c9uWK1HlIfsJuuifMNHK/E8Ry/8gJfBz/kjStHfHC7oFg8Itl23PcHNZXiFXCAwSYqvTSNe6Prlse1UEZNy22ndwx2RaqkZMPPrFyCQpjc7d2Uhanf782W13uZyjCnfLj4eKKXPryopKBfPkRAnAUYmQWxWjN1x3zjAHEKTqs7iWa10ygZtOFZqFoqp/f1wxNFFskx2Kr0fLcxwK8ORlIdBw1AyfH3PwAy3whz6VR5q0OwhuMaLU8AIou2d8d7gzokaF2ZH2EXaALJmGwbFJ/O57le2ZUwgmtOM0BrIUBWWo7Dtj9WcJvNOy0vidcLresrz2WAtE9D1Q7zJR2pzm7OQwtMYSV1+Hw2sF4f7GEJ6zWjBBUtVyDjA8ac/O6MIFxAS2DPMCbwOpil8wn/e7OeASUh5jO0VFoJ5d9Yxgx6btG9SzYLeC1S71X/SqDhsTOjOxiQ4FwBydOposvcmleW4UHkIe/ffNgjQ1cRxGvAx9p5ppgp0rQcS7exUNlp09OJFzD/L/aF/fndvl3yvLpiSug8aat+SRwr28t1bFBwFSlJhRhSwchaJwERSIRnwpTUmaTqMm6XMy2NxIKMFuxq 5r9YRV/r mOudem1VAt+smyLR/sF/DVuL1f8t3GXuRlSj9170vV3T4TQebyf4cSmhro+NolZEoqK5RjHTfbdkRXcLW8Kv/N2BinCURICNxeV1rI+lR944OAyURAcybrR0/DeAAvcL/vrjUrm8EzYxM6Iy2ciNxVoqjLgD/gU7E+FvsVUhPb+pgdC2koYSCAOnwohFAktMtJ0ClcwObmH8xEwrtb6Zvh22TouN32BeHDDm3Vu1qs0+e1jbyJmz/2PVYjgo5hm+uA2vvoQjVSZ8nzGDiGjZ8bcZp4Q== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Apr 20, 2026 at 08:01:19AM +0000, Gorbunov Ivan wrote: > The current atomic-based page refcount implementation treats zero > counter as dead and requires a compare-and-swap loop in folio_try_get() > to prevent incrementing a dead refcount. This CAS loop acts as a > serialization point and can become a significant bottleneck during > high-frequency file read operations. If the file read is high-frequency, then for the page refcount to be the bottleneck, they must be small reads? Have you looked at this patch? https://lore.kernel.org/all/20251017141536.577466-1-kirill@shutemov.name/