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=-7.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 4D563C433E6 for ; Tue, 2 Feb 2021 17:27:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E931964ECE for ; Tue, 2 Feb 2021 17:27:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234231AbhBBR12 (ORCPT ); Tue, 2 Feb 2021 12:27:28 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:38691 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233921AbhBBOOG (ORCPT ); Tue, 2 Feb 2021 09:14:06 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612275160; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=mAXEVjxGkaVgIUFhfXA1HRN3FgtOlJcIpAQw2h/beVM=; b=eKDUxb1+pqSJGwixp0bJb9IpFbLQ2YWSNtr9y6B5b9tHnfKB8XWwqMi4lg2wcz689fqN+7 ixbEtjubRl8BQ3SthB9ROO4tXppvD18dReUGmXO7MA7mXPXT1SkBZZqlAPN5rjZaPaek3k ft4gaH36hp6hgsL1Zdqrv2sUA+94Msc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-460-DO7GaD-qPMSuJ9daYkp31A-1; Tue, 02 Feb 2021 09:12:35 -0500 X-MC-Unique: DO7GaD-qPMSuJ9daYkp31A-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B117B100A8E8; Tue, 2 Feb 2021 14:12:30 +0000 (UTC) Received: from [10.36.114.148] (ovpn-114-148.ams2.redhat.com [10.36.114.148]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6CE915B4A7; Tue, 2 Feb 2021 14:12:22 +0000 (UTC) To: Michal Hocko Cc: Mike Rapoport , James Bottomley , Andrew Morton , Alexander Viro , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christopher Lameter , Dan Williams , Dave Hansen , Elena Reshetova , "H. Peter Anvin" , Ingo Molnar , "Kirill A. Shutemov" , Matthew Wilcox , Mark Rutland , Mike Rapoport , Michael Kerrisk , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Rick Edgecombe , Roman Gushchin , Shakeel Butt , Shuah Khan , Thomas Gleixner , Tycho Andersen , Will Deacon , linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org, x86@kernel.org, Hagen Paul Pfeifer , Palmer Dabbelt References: <303f348d-e494-e386-d1f5-14505b5da254@redhat.com> <20210126120823.GM827@dhcp22.suse.cz> <20210128092259.GB242749@kernel.org> <73738cda43236b5ac2714e228af362b67a712f5d.camel@linux.ibm.com> <6de6b9f9c2d28eecc494e7db6ffbedc262317e11.camel@linux.ibm.com> <20210202124857.GN242749@kernel.org> <6653288a-dd02-f9de-ef6a-e8d567d71d53@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Subject: Re: [PATCH v16 07/11] secretmem: use PMD-size pages to amortize direct map fragmentation Message-ID: <211f0214-1868-a5be-9428-7acfc3b73993@redhat.com> Date: Tue, 2 Feb 2021 15:12:21 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On 02.02.21 14:32, Michal Hocko wrote: > On Tue 02-02-21 14:14:09, David Hildenbrand wrote: > [...] >> As already expressed, I dislike allowing user space to consume an unlimited >> number unmovable/unmigratable allocations. We already have that in some >> cases with huge pages (when the arch does not support migration) - but there >> we can at least manage the consumption using the whole max/reserved/free/... >> infrastructure. In addition, adding arch support for migration shouldn't be >> too complicated. > > Well, mlock is not too different here as well. Hugepages are arguably an > easier model because it requires an explicit pre-configuration by an > admin. Mlock doesn't have anything like that. Please also note that > while mlock pages are migrateable by default, this is not the case in > general because they can be configured to disalow migration to prevent > from minor page faults as some workloads require that (e.g. RT). Yeah, however that is a very special case. In most cases mlock() simply prevents swapping, you still have movable pages you can place anywhere you like (including on ZONE_MOVABLE). > Another example is ramdisk or even tmpfs (with swap storage depleted or > not configured). Both are PITA from the OOM POV but they are manageable > if people are careful. Right, but again, special cases - e.g., tmpfs explicitly has to be resized. > If secretmem behaves along those existing models > then we know what to expect at least. I think secretmem behaves much more like longterm GUP right now ("unmigratable", "lifetime controlled by user space", "cannot go on CMA/ZONE_MOVABLE"). I'd either want to reasonably well control/limit it or make it behave more like mlocked pages. -- Thanks, David / dhildenb