From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4C1BACCFA13 for ; Thu, 30 Apr 2026 12:37:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=z/YmOm364MLgKTekAQcMcyvI8WeWgw/tah25yx/smkI=; b=Gu8KtVVAUNAVtUHdffib0umUUF uuriMDKmOhojZu5XZRr6n2o1LbfCQUP+HyWREa8rNpZSIF9Dg8XJjr3/AJXYwz9y2nRW9GO7DWuVV PyvIFsRg10kEn9vRyk9WJmRbVDKgK+Hc1rEkJC4lVLgt0lPk+4xy9mv++BKZdix7fP/1tkAETM7L5 KeJTUyXaM86dTRjYYqDf4fPKsCjgTzPfcK4Phrxx27DR2DvfVww0d6mBrbceqgYJ3vxQHr5pPhbij m1U3pivJc1aOCZRGozKLBaMc0/vrbAmLZcqbjq5X/CJT9rz5AkiPrV5cAxJDlFuuzG4s//A5BSWmT 9AOrHKcw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wIQdv-00000005TCp-3Xh9; Thu, 30 Apr 2026 12:37:23 +0000 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wIQdu-00000005TCT-2lkC; Thu, 30 Apr 2026 12:37:22 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260430040427.4672-1-baohua@kernel.org> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.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.