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bh=z/YmOm364MLgKTekAQcMcyvI8WeWgw/tah25yx/smkI=; b=OVEuy04ZJAcBaKwk8cxrvq7Tt5 XT82G1jqIw0PkdnsdUVlw+7QCza/twzfpnsx2kAqSxg7PTBm0kBexRmE2xwQdNMnRyEnteCqgWzIn pGkT+4EL2ASd9E3W3zW7yYDg3jwhiv9VQjK8KHyhy+eeJpz4dqkaLDP6PuXP1J2eRrmKWTk8F9tKW CawTIBqH87INZkKlSIMhv2zjWwFJnSYo+4xe4HesOWqi4rik/G82R6PqrkV5YTcbPWHu29MwOaGgj jzKa0vAXrEAUkOYciTPNLGggQqRFBNNvsXY3E40Q+hwIcMj9vZmSiwG6RsfdSJ+eO9OpzQbCzsngB wKLRaGvg==; 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> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260430040427.4672-1-baohua@kernel.org> 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.