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,URIBL_BLOCKED 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 473F0C4CECE for ; Wed, 11 Mar 2020 22:21:23 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3B5112074F for ; Wed, 11 Mar 2020 22:21:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3B5112074F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arndb.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CFB8D6B0005; Wed, 11 Mar 2020 18:21:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CAC626B0006; 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Wed, 11 Mar 2020 23:21:19 +0100 Received: by mail-qk1-f174.google.com with SMTP id u25so3799729qkk.3 for ; Wed, 11 Mar 2020 15:21:18 -0700 (PDT) X-Gm-Message-State: ANhLgQ0W04lZxyclSv5CvzKKDDtMFlUTdOBr3H1xtFlE6O6g5LAJ6+lD 8Uz1DY5WfNsNIfN+w94PX4/r9XF1kHnUb3peuY0= X-Google-Smtp-Source: ADFU+vtUX6596ckwbsQtKLPYKkjWdRNNv2OExbN7pWVykWRKgnRWddSMydtufZDaxYnGmzl5giJGitq9nSLOAiz/v+U= X-Received: by 2002:a37:8707:: with SMTP id j7mr2513764qkd.394.1583965277788; Wed, 11 Mar 2020 15:21:17 -0700 (PDT) MIME-Version: 1.0 References: <671b05bc-7237-7422-3ece-f1a4a3652c92@oracle.com> <7c4c1459-60d5-24c8-6eb9-da299ead99ea@oracle.com> <20200306203439.peytghdqragjfhdx@kahuna> <20200309155945.GA4124965@arrakis.emea.arm.com> <20200309160919.GM25745@shell.armlinux.org.uk> <20200311142905.GI3216816@arrakis.emea.arm.com> <20200311172631.GN3216816@arrakis.emea.arm.com> In-Reply-To: <20200311172631.GN3216816@arrakis.emea.arm.com> From: Arnd Bergmann Date: Wed, 11 Mar 2020 23:21:01 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] vfs: keep inodes with page cache off the inode shrinker LRU To: Catalin Marinas Cc: Russell King - ARM Linux admin , Nishanth Menon , Santosh Shilimkar , Tero Kristo , Linux ARM , Michal Hocko , Rik van Riel , Santosh Shilimkar , Dave Chinner , 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:uoEdR+hxEdtR+T+R2S18ahIeHsR/QZpT2BOseJgsEps9FSUlctq 3Ugmxu3zpO2tLd71tjd2MnUMvJ5V9YNGRHGohG+KdhnBvcfYgh8jeVL2XbPHtte2leobZvX 84ymI8bxsmhMGjHKmEqIPPHuJi+RWfGbhfwcRN34IrOQ5qlHSZkFnI5eERxoGKKeehZSVib u4E3Yq0drZT/2HCZ0M8BQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:e1InS7QJpkg=:zUkOgeqntQpi/RZh0maYwn fR/XZ+z0llME8GLaCnp0JTn8LhZwXCpfYgl8fO1+U9iZJTDfdF7LeTR9vF7P7230fjh+mwrHR Sslqeh6Zu9MoycLm0MjmzmjJt8uBkeU8GAr8D1rUmzMCIbcrBN/IddlKP4T/XrsleBjPrxf/k eXNUUcLRlaGYDuxpdyyon3kTh1sOGUk+d9QF/swIPEV7ogwJjcHkcYVAhw8S7Dc9Ba6wzy+7R irVjBOcpN/FLvcKD2s0N56IDz03RVXDZAUDW08OjTMlX4UnwMRXyLHc1iKlZnobZqEGTvUmGp uHmlNdLMkl9Q48osjQ5EUrLqNcstONJDs5pb1vweMljlEG+feFAV8/dnLzKqJrscaRjp5wOU4 zGsAszvzYikqJlzUBh1GdILqp/zHtgi32/fi/G6bnPKpy4KyAukb9r7/ys7vfv2P+nCQKf2DB Hnln5NiCaWNkLa0HeuRlUmxi2P2mTk3bd7yzAKzrxrfB+wTRGocWRR/hF5yOn2Ul0wiMmBAl9 xqiQ2VGdYNlcS4JkK2/QZuyZPf+uRid4LmEh9QM6soZAx0QOHFPhrPrU38+KQxlAk2mriyS82 co5QAfbkX3CYISC87TSRP3phbPsFNYyzhz+1sFloppjHAVoXPKhGuUP6mCR1hLyZG6PZpXwgF I7/uKNjXCBV0gxIHpsH+FgatipwbM4ypBVluJZi/1KgEoUchv3Su53j6pYXZucdNWvIMtfOFs agk2YqxuG+rILTRBoXJ13wWoqwTCvOMvmsGhHAfv/jMPZBuTLIv4v9fwf5xhC/d/YfX2kJ6oX SXsJFPgmWiGlIM946MSFUQIWNDvkMggvDKmf/dbTLfAqRMPfYA= 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 Wed, Mar 11, 2020 at 6:26 PM Catalin Marinas wrote: > On Wed, Mar 11, 2020 at 05:59:53PM +0100, Arnd Bergmann wrote: > > On Wed, Mar 11, 2020 at 3:29 PM Catalin Marinas wrote: > > Do you have an estimate of how long writing to TTBR0_64 takes on Cortex-A7 > > and A15, respectively? > > I don't have numbers but it's usually not cheap since you need an ISB to > synchronise the context after TTBR0 update (basically flushing the > pipeline). Ok. > > Another way might be to use a use a temporary buffer that is already > > mapped, and add a memcpy() through L1-cache to reduce the number > > of ttbr0 changes. The buffer would probably have to be on the stack, > > which limits the size, but for large copies get_user_pages()+memcpy() > > may end up being faster anyway. > > IIRC, the x86 attempt from Ingo some years ago was using > get_user_pages() for uaccess. Depending on the size of the buffer, this > may be faster than copying twice. I guess the tradeoffs for that were rather different, as x86 back then had no ASIDs, so changing the page tables required a full TLB flush. Arnd