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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CF7DCC3F2C6 for ; Mon, 9 Mar 2020 15:59:52 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9A76C24649 for ; Mon, 9 Mar 2020 15:59:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9A76C24649 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 28B3E6B0005; Mon, 9 Mar 2020 11:59:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 214B76B0006; Mon, 9 Mar 2020 11:59:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0B5876B0007; Mon, 9 Mar 2020 11:59:52 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0069.hostedemail.com [216.40.44.69]) by kanga.kvack.org (Postfix) with ESMTP id E0A7D6B0005 for ; Mon, 9 Mar 2020 11:59:51 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id A764E181AC9C6 for ; Mon, 9 Mar 2020 15:59:51 +0000 (UTC) X-FDA: 76576284582.17.owner18_560b3f4e4ac36 X-HE-Tag: owner18_560b3f4e4ac36 X-Filterd-Recvd-Size: 3294 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf08.hostedemail.com (Postfix) with ESMTP for ; Mon, 9 Mar 2020 15:59:51 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4142930E; Mon, 9 Mar 2020 08:59:50 -0700 (PDT) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.71]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B3D203F534; Mon, 9 Mar 2020 08:59:47 -0700 (PDT) Date: Mon, 9 Mar 2020 15:59:45 +0000 From: Catalin Marinas To: Arnd Bergmann Cc: Nishanth Menon , Santosh Shilimkar , Tero Kristo , Linux ARM , Michal Hocko , Rik van Riel , Santosh Shilimkar , Dave Chinner , Russell King - ARM Linux admin , Linux Kernel Mailing List , Linux-MM , Yafang Shao , Al Viro , Johannes Weiner , linux-fsdevel , kernel-team@fb.com, Kishon Vijay Abraham I , Linus Torvalds , Andrew Morton , Roman Gushchin Subject: Re: [PATCH] vfs: keep inodes with page cache off the inode shrinker LRU Message-ID: <20200309155945.GA4124965@arrakis.emea.arm.com> References: <20200211164701.4ac88d9222e23d1e8cc57c51@linux-foundation.org> <20200212085004.GL25745@shell.armlinux.org.uk> <671b05bc-7237-7422-3ece-f1a4a3652c92@oracle.com> <7c4c1459-60d5-24c8-6eb9-da299ead99ea@oracle.com> <20200306203439.peytghdqragjfhdx@kahuna> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, Mar 08, 2020 at 11:58:52AM +0100, Arnd Bergmann wrote: > - revisit CONFIG_VMSPLIT_4G_4G for arm32 (and maybe mips32) > to see if it can be done, and what the overhead is. This is probably > more work than the others combined, but also the most promising > as it allows the most user address space and physical ram to be used. A rough outline of such support (and likely to miss some corner cases): 1. Kernel runs with its own ASID and non-global page tables. 2. Trampoline code on exception entry/exit to handle the TTBR0 switching between user and kernel. 3. uaccess routines need to be reworked to pin the user pages in memory (get_user_pages()) and access them via the kernel address space. Point 3 is probably the ugliest and it would introduce a noticeable slowdown in certain syscalls. -- Catalin