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 E32C5CD3423 for ; Fri, 1 May 2026 14:57:10 +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=GWaEOZ6T8RZshC5VNeX+VR+c38seOstsZgFtVZK1Yb0=; b=2xcEc8e6jp4e6blregbk7cAjZL jrR+sZhfyCHweNBgtRiIKdX2GcN3N1I1LsOAKxnz8EfZrWMVVmPlGvuhCdlHdJCNi7KzhAnajgjat STd7CeS/9tuCPy21ZFqtWy8rR5FKt+NycInEFD2zVtv49p7t/0e4ZkoM0xeNj10BZcitoS1lmPMyS fQTt/ntF7LNL5qUh+ZKC/QZCawxcfEAucWUUIzEiA+1rTYGSXSz8v4/aQXk2Rx8WrVEJjDImSy7bq AcK0o3M1Wg0Am6KVMhJK2NkaPyalaXJj7LC46Nlzkc/mGg3Io06u5rJ8MkR4ikBrow9uq5YrZGQnc vQAX02bA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wIpId-00000007Iuy-04Sw; Fri, 01 May 2026 14:57:03 +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 1wIpIc-00000007Iui-1qUc; Fri, 01 May 2026 14:57:02 +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=GWaEOZ6T8RZshC5VNeX+VR+c38seOstsZgFtVZK1Yb0=; b=Er8GF8z4i4fcdoqldcSz6UdIrK 0uV2fMmb401OPsbWUDQlEgY0WImYvRoaOS/51Kt7cci4PwM0IwWZmDRUbGXw7O9IkTUTcXx4Dq2Om 1ySnKP5ZPsmA0cdTKwQEUsbejJKOkDxp+xsnqOc9et7bCG9WzZFKFYNxcz4UjijcH9lNIaYGg9axV D8CvZuRnVnBvGs0WeFCpwaRxMrcj+ZmM+kVA2Q+aDmR35tDfpqtDlNjfzVDU0ieNT7dT3nkuFY8KO oBaeuIlQkfSbM8D3+gtqA/Kl4BULEQcG2OPtDBswRpN88NbjoIlZE7bl29JItAlrzNVWRNazfWERT lB1uWyaw==; Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1wIpIN-00000008wbR-3iIK; Fri, 01 May 2026 14:56:48 +0000 Date: Fri, 1 May 2026 15:56:47 +0100 From: Matthew Wilcox To: Barry Song 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: 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 Fri, May 01, 2026 at 06:49:58AM +0800, Barry Song wrote: > 1. There is no deterministic latency for I/O completion. It depends on > both the hardware and the software stack (bio/request queues and the > block scheduler). Sometimes the latency is short; at other times it can > be quite long. In such cases, a high-priority thread performing operations > such as mprotect, unmap, prctl_set_vma, or madvise may be forced to wait > for an unpredictable amount of time. But does that actually happen? I find it hard to believe that thread A unmaps a VMA while thread B is in the middle of taking a page fault in that same VMA. mprotect() and madvise() are more likely to happen, but it still seems really unlikely to me.