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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1wIQdn-00000007Dwg-0sn0; Thu, 30 Apr 2026 12:37:15 +0000 Date: Thu, 30 Apr 2026 13:37:14 +0100 From: Matthew Wilcox To: "Barry Song (Xiaomi)" Cc: akpm@linux-foundation.org, linux-mm@kvack.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, jack@suse.cz, pfalcato@suse.de, wanglian@kylinos.cn, chentao@kylinos.cn, lianux.mm@gmail.com, kunwu.chan@gmail.com, liyangouwen1@oppo.com, chrisl@kernel.org, kasong@tencent.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, youngjun.park@lge.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org Subject: Re: [PATCH v2 0/5] mm: reduce mmap_lock contention and improve page fault performance Message-ID: References: <20260430040427.4672-1-baohua@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260430040427.4672-1-baohua@kernel.org> X-Rspam-User: X-Rspamd-Queue-Id: C338DC0009 X-Rspamd-Server: rspam04 X-Stat-Signature: 5igxnwqm57saobypsczjnfog1mo19ui5 X-HE-Tag: 1777552642-868833 X-HE-Meta: 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 AbdK//jo 2vAEa1s6eoJAHM7W9LDrEyoeuM/F1EzDlbzVn0eTXyqyPjIj3YWk9D4Q5cvah7z3fZbhz9DPG5H0nuhVg35U+GHMpkdrzb2oIj4Fv6HdpVICTHjv9EYdKtx9ka7rSjSiB+UuJeTECVjxi9BaGSgF5/2Z22Oj+hjGXWwi/vwnU6jvpRUTGZ2Gbd4S3HbH0T7yAY3IUV9IKq7GXpDnu+d/vv/tGsvCtv3eOq+Q8Z8ypd5U3BO0s2p5XtylWyFRoO37Vfrlwn0eHCeV3phFWaeAeufkkENb6X3qibeagjaNQVwa8EGCDR38cuo/0vIE1xZvNwFFRZZdK1TCtPhhRuO0Snae0TSjkAKoUaQkP95jXOmyKqXkdhX1WV4ye+w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Apr 30, 2026 at 12:04:22PM +0800, Barry Song (Xiaomi) wrote: > (1) If we need to wait for I/O completion, we still drop the per-VMA lock, as > current page fault handling already does. Holding it for too long may introduce > various priority inversion issues on mobile devices. After I/O completes, we > retry the page fault with the per-VMA lock, rather than falling back to > mmap_lock. You're going to have to do better than that. You know I hate the additional complexity you're adding. You need to explain why my idea of ripping out all the complexity now that we have per-VMA locks doesn't work.