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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 1360CC433E0 for ; Tue, 2 Feb 2021 13:36:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C52C664DBD for ; Tue, 2 Feb 2021 13:36:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231874AbhBBNfx (ORCPT ); Tue, 2 Feb 2021 08:35:53 -0500 Received: from mx2.suse.de ([195.135.220.15]:42098 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232490AbhBBNdB (ORCPT ); Tue, 2 Feb 2021 08:33:01 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1612272735; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qhASYy52HrQdJQILCHxBxIDs1mcnSSfDvbUg8Hv9Huk=; b=O35yhETCIJcmvITBzmA06eT7x4pieJO9swql+e/dEuWJvoBkcPrcGAQe2sM2r3gNYCJ97G cutl0j+I7mXW23xuyyuYKFCdVv7+WC+a62VtrpsBAxAPUoJKjRiqBrbLEGz3xn0w2G09n8 8FyL2zHquLohp9unYR6VoEzGZD+347Q= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id B66D6AF92; Tue, 2 Feb 2021 13:32:14 +0000 (UTC) Date: Tue, 2 Feb 2021 14:32:13 +0100 From: Michal Hocko To: David Hildenbrand 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 Subject: Re: [PATCH v16 07/11] secretmem: use PMD-size pages to amortize direct map fragmentation Message-ID: 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6653288a-dd02-f9de-ef6a-e8d567d71d53@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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). 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. If secretmem behaves along those existing models then we know what to expect at least. -- Michal Hocko SUSE Labs