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[209.132.180.67]) by mx.google.com with ESMTP id e2si2094118otq.309.2020.03.08.03.59.35; Sun, 08 Mar 2020 03:59:47 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726336AbgCHK7N (ORCPT + 99 others); Sun, 8 Mar 2020 06:59:13 -0400 Received: from mout.kundenserver.de ([212.227.126.133]:39477 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726298AbgCHK7M (ORCPT ); Sun, 8 Mar 2020 06:59:12 -0400 Received: from mail-qk1-f174.google.com ([209.85.222.174]) by mrelayeu.kundenserver.de (mreue009 [212.227.15.129]) with ESMTPSA (Nemesis) id 1Mbj3e-1jlai033hm-00dEKm; Sun, 08 Mar 2020 11:59:10 +0100 Received: by mail-qk1-f174.google.com with SMTP id e16so6627426qkl.6; Sun, 08 Mar 2020 03:59:10 -0700 (PDT) X-Gm-Message-State: ANhLgQ2tx6nBbu9BZm/VaD/fTr4TtFrqC3GIVOZxN7EMTYWXNWntJKQZ zc+o8+fAWYojr+gWZYmaEcXHUZ3BLPyvp3okdOI= X-Received: by 2002:a37:b984:: with SMTP id j126mr10069404qkf.3.1583665149525; Sun, 08 Mar 2020 03:59:09 -0700 (PDT) MIME-Version: 1.0 References: <20200211193101.GA178975@cmpxchg.org> <20200211154438.14ef129db412574c5576facf@linux-foundation.org> <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> In-Reply-To: <20200306203439.peytghdqragjfhdx@kahuna> From: Arnd Bergmann Date: Sun, 8 Mar 2020 11:58:52 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] vfs: keep inodes with page cache off the inode shrinker LRU To: Nishanth Menon Cc: Santosh Shilimkar , Tero Kristo , Linux ARM , Michal Hocko , Rik van Riel , Catalin Marinas , 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 Content-Type: text/plain; charset="UTF-8" X-Provags-ID: V03:K1:DheoUgROyUqGqcI4pA5GCMcqVMpjZnw/PkO7ntC55mREQOoV9L4 WBFLPxlDsBzM+eNxaHnH9mbPs4MvCWGAN4dTsJqJ4gGPYS0YCQHu+LCqgRBVPwJmEAAhcQq 0+j6SLlqfFXktNJQY1+F5SVRW2yRUVUklyXLqA2CO+C/fEXCdia+ytDo2EMv+8X/u9bL1aQ yfyzwT91oiDBce55wyAkw== X-Spam-Flag: NO X-UI-Out-Filterresults: notjunk:1;V03:K0:kpVgpSBnjp0=:P9TLuf2nR248rJ8L86D9iP +RrntFKmM6RoDUEE4PdJKFAY+Qm/Kl4/s1ujBSLuXSQKmDltLoJETpzA6Feiv+bqUo6UyE4Yg +h2xCM/v37Wo9EYGuIhRPU3AwXiPUBscwjZ0xFTNOnUYU9/Xyl/jeZkEIa5Hm3d3lZQYWWd4I mKPwi9CStKxjxjLBvU1aacACOT0RpAhhItc3/szQ9+SRbw4nzZP2u2TIWCl+9g9tXDekDwfbH QGZo627rcEMyqVgEVOtsUvhS4afpjf/r5l936nlFTLsQA0nkTlqME1J4fRhw7X1P+DewPL9xg H9p8B3IUNgBS9vULYmhCJsjKRb4v1VY7KouLymIWxwRiNXp92QM0J2TpRwyyWD5JN85y9xRuJ EiLBsumJ42Y9AfWHrdIWUOFSFb9pTnWCcRdl6vDI4TgyqGyVmOVtIl1vxPqih1seaxtsj+CXm 1gcT6jaXgZnt2r23ZlHAttrLLJc+RsRnbR7bToQF9uZ+62+T23cL7zkQgv49oI42MSB9PFLW2 dRzThnm0+JiGvyb6t/L+BXVwdklJqPcNAeumOHv0uum/NKJzCJJFilHwv4ldrojcv8cywbpGz L4XjxQVyDCtgZOdffNhu26UiznP5wFp2BiT1p/pVahnXBwDba3gnrtc2NI4OmRHJyFBhR/EY1 GUyR0LWLci5rXjAlUYXfsxwJXt+Mgk8I3aooMw/oiqz6V6e47oMKjY6CxK0EgkCWA6vULoR/l wz9tODNKHpvug0cMqo9uzvdZpZAiwhBfJj8Lard3xYfEivXT67lVQczgvXMFExXVDPEVl1YfR FyjXlq039IuAs3Q0gsFs3O7Sac6QRjgaJRgJRgH0MzLgVk2c5c= Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 6, 2020 at 9:36 PM Nishanth Menon wrote: > On 13:11-20200226, santosh.shilimkar@oracle.com wrote: > > ~few 1000s still relevant spread between 4G and 8G (confirmed that both > are present, relevant and in use). > > I wish we could sunset, but unfortunately, I am told(and agree) > that we should'nt just leave products (and these are long term > products stuck in critical parts in our world) hanging in the air, and > migrations to newer kernel do still take place periodically (the best > I can talk in public forum at least). Thank you for the clear answer! I agree we should certainly not break any such use cases, and for the 8GB case there is not really a good replacement (using zram/zswap instead of highmem could work for some new workloads, but would be a rather risky change for an upgrade on already deployed systems). I hope it's ok to ask the same question every few years until you are reasonably sure that the users are ready to stop upgrading kernels beyond the following LTS kernel version. We can also do the same thing for the other 32-bit platforms that exceed the maximum amount of lowmem, and document which ones are known. In the meantime, it would seem useful to increase the amount of lowmem that can be used by default, using a combination of some of the changes mentioned earlier - add a VMSPLIT_2G_OPT config option for non-LPAE ARM kernels to handle the common i.MX6 case with 2GB of RAM without highmem - make VMSPLIT_2G_OPT (without LPAE) or VMSPLIT_2G (with LPAE) the default in most ARM defconfig files as well as distros, and disable highmem where possible, to see what breaks. - extend zswap to use all the available high memory for swap space when highmem is disabled. - 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. Arnd