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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 7F86EC43461 for ; Wed, 5 May 2021 01:39:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 661C461423 for ; Wed, 5 May 2021 01:39:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232141AbhEEBkK (ORCPT ); Tue, 4 May 2021 21:40:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:43498 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232034AbhEEBkI (ORCPT ); Tue, 4 May 2021 21:40:08 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6D07061426; Wed, 5 May 2021 01:39:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1620178753; bh=DQYt2xA/WAN2ks5xElySlfaBkCQiKa/IGIqXpFZDNpM=; h=Date:From:To:Subject:In-Reply-To:From; b=DpYAG/FgZbHgPWzqOMOt3XAGaSIRZep7MZKS4qQFDUFQl0NjH2mFan5lhXMH4iQ4A pKo1Nu9F+og77YYU4dvCXAj9n1yPS1j2/m/4fBukCskjiTUEccxytJaZKKVus9pK6G +jRTOQex2yQV3r80HoeyzQfzbw2dUs/ifPzOfHGU= Date: Tue, 04 May 2021 18:39:12 -0700 From: Andrew Morton To: akpm@linux-foundation.org, dan.j.williams@intel.com, david@redhat.com, iamjoonsoo.kim@lge.com, ira.weiny@intel.com, jgg@nvidia.com, jgg@ziepe.ca, jhubbard@nvidia.com, jmorris@namei.org, linux-mm@kvack.org, mgorman@suse.de, mhocko@kernel.org, mhocko@suse.com, mike.kravetz@oracle.com, mingo@redhat.com, mm-commits@vger.kernel.org, osalvador@suse.de, pasha.tatashin@soleen.com, peterz@infradead.org, rientjes@google.com, rostedt@goodmis.org, sashal@kernel.org, torvalds@linux-foundation.org, tyhicks@linux.microsoft.com, vbabka@suse.cz, willy@infradead.org Subject: [patch 119/143] memory-hotplug.rst: add a note about ZONE_MOVABLE and page pinning Message-ID: <20210505013912.5XQuMvU8N%akpm@linux-foundation.org> In-Reply-To: <20210504183219.a3cc46aee4013d77402276c5@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Pavel Tatashin Subject: memory-hotplug.rst: add a note about ZONE_MOVABLE and page pinning Document the special handling of page pinning when ZONE_MOVABLE present. Link: https://lkml.kernel.org/r/20210215161349.246722-11-pasha.tatashin@soleen.com Signed-off-by: Pavel Tatashin Suggested-by: David Hildenbrand Acked-by: Michal Hocko Cc: Dan Williams Cc: David Rientjes Cc: Ingo Molnar Cc: Ira Weiny Cc: James Morris Cc: Jason Gunthorpe Cc: Jason Gunthorpe Cc: John Hubbard Cc: Joonsoo Kim Cc: Matthew Wilcox Cc: Mel Gorman Cc: Michal Hocko Cc: Mike Kravetz Cc: Oscar Salvador Cc: Peter Zijlstra Cc: Sasha Levin Cc: Steven Rostedt (VMware) Cc: Tyler Hicks Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- Documentation/admin-guide/mm/memory-hotplug.rst | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/Documentation/admin-guide/mm/memory-hotplug.rst~memory-hotplugrst-add-a-note-about-zone_movable-and-page-pinning +++ a/Documentation/admin-guide/mm/memory-hotplug.rst @@ -357,6 +357,15 @@ creates ZONE_MOVABLE as following. Unfortunately, there is no information to show which memory block belongs to ZONE_MOVABLE. This is TBD. +.. note:: + Techniques that rely on long-term pinnings of memory (especially, RDMA and + vfio) are fundamentally problematic with ZONE_MOVABLE and, therefore, memory + hot remove. Pinned pages cannot reside on ZONE_MOVABLE, to guarantee that + memory can still get hot removed - be aware that pinning can fail even if + there is plenty of free memory in ZONE_MOVABLE. In addition, using + ZONE_MOVABLE might make page pinning more expensive, because pages have to be + migrated off that zone first. + .. _memory_hotplug_how_to_offline_memory: How to offline memory _