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 8E45BC2BBCF for ; Fri, 18 Dec 2020 09:44:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 63BAD23A80 for ; Fri, 18 Dec 2020 09:44:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733081AbgLRJoO (ORCPT ); Fri, 18 Dec 2020 04:44:14 -0500 Received: from mx2.suse.de ([195.135.220.15]:56658 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725884AbgLRJoN (ORCPT ); Fri, 18 Dec 2020 04:44:13 -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=1608284606; 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=Kns51nghtkz6ndAww0GyVqmKXCNEXcevy0MsQVndr/Q=; b=BeXlxK9M4wgEVguLtRScCNhQjzll21viDpb7mjSOySSiwfuIAFOm6LrI5elHH55KfG81Qf t2uxwmdt6qwwCserYXTFBNQKHazYMkB5euGcVgHvByC/5JFQlY3mt5eyvJl7ihJWVtnK4X 63LP2G/AU+lJ0CBSxgu5n2vySg4Nto0= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 29927ACC4; Fri, 18 Dec 2020 09:43:26 +0000 (UTC) Date: Fri, 18 Dec 2020 10:43:24 +0100 From: Michal Hocko To: Pavel Tatashin Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, vbabka@suse.cz, david@redhat.com, osalvador@suse.de, dan.j.williams@intel.com, sashal@kernel.org, tyhicks@linux.microsoft.com, iamjoonsoo.kim@lge.com, mike.kravetz@oracle.com, rostedt@goodmis.org, mingo@redhat.com, jgg@ziepe.ca, peterz@infradead.org, mgorman@suse.de, willy@infradead.org, rientjes@google.com, jhubbard@nvidia.com, linux-doc@vger.kernel.org, ira.weiny@intel.com, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v4 05/10] mm/gup: migrate pinned pages out of movable zone Message-ID: <20201218094324.GT32193@dhcp22.suse.cz> References: <20201217185243.3288048-1-pasha.tatashin@soleen.com> <20201217185243.3288048-6-pasha.tatashin@soleen.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201217185243.3288048-6-pasha.tatashin@soleen.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 17-12-20 13:52:38, Pavel Tatashin wrote: > + * 1. Pinned pages: (long-term) pinning of movable pages is avoided > + * when pages are pinned and faulted, but it is still possible that > + * address space already has pages in ZONE_MOVABLE at the time when > + * pages are pinned (i.e. user has touches that memory before > + * pinning). In such case we try to migrate them to a different zone, > + * but if migration fails the pages can still end-up pinned in > + * ZONE_MOVABLE. In such case, memory offlining might retry a long > + * time and will only succeed once user application unpins pages. I still dislike this. Pinning can fail so there shouldn't be any reasons to break MOVABLE constrain for something that can be handled. If anything there should be a very good reasoning behind this decision documented. -- Michal Hocko SUSE Labs