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=-5.2 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 3C650C433E0 for ; Tue, 2 Feb 2021 14:12:43 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BC6E964EAC for ; Tue, 2 Feb 2021 14:12:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BC6E964EAC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 151966B0072; Tue, 2 Feb 2021 09:12:42 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 0FFED6B0073; Tue, 2 Feb 2021 09:12:42 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EBAE36B0075; Tue, 2 Feb 2021 09:12:41 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0023.hostedemail.com [216.40.44.23]) by kanga.kvack.org (Postfix) with ESMTP id D3CC16B0072 for ; Tue, 2 Feb 2021 09:12:41 -0500 (EST) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 98AB78249980 for ; Tue, 2 Feb 2021 14:12:41 +0000 (UTC) X-FDA: 77773518522.27.blade59_0915d9b275cb Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin27.hostedemail.com (Postfix) with ESMTP id 62CAB3D66D for ; Tue, 2 Feb 2021 14:12:41 +0000 (UTC) X-HE-Tag: blade59_0915d9b275cb X-Filterd-Recvd-Size: 5955 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) by imf45.hostedemail.com (Postfix) with ESMTP for ; Tue, 2 Feb 2021 14:12:40 +0000 (UTC) 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 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Content-Transfer-Encoding: quoted-printable 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 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 unli= mited >> number unmovable/unmigratable allocations. We already have that in som= e >> 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/fr= ee/... >> infrastructure. In addition, adding arch support for migration shouldn= 't be >> too complicated. >=20 > Well, mlock is not too different here as well. Hugepages are arguably a= n > 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=20 prevents swapping, you still have movable pages you can place anywhere=20 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 resize= d. > 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=20 ("unmigratable", "lifetime controlled by user space", "cannot go on=20 CMA/ZONE_MOVABLE"). I'd either want to reasonably well control/limit it=20 or make it behave more like mlocked pages. --=20 Thanks, David / dhildenb