From patchwork Tue Oct 13 23:55:35 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 11836467 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9F7CB61C for ; Tue, 13 Oct 2020 23:55:40 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 63F3B2222E for ; Tue, 13 Oct 2020 23:55:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="CMP9ERJL" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 63F3B2222E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 699976B0126; Tue, 13 Oct 2020 19:55:39 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 64AD16B0127; Tue, 13 Oct 2020 19:55:39 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 539DD6B0128; Tue, 13 Oct 2020 19:55:39 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0172.hostedemail.com [216.40.44.172]) by kanga.kvack.org (Postfix) with ESMTP id 27FC86B0126 for ; Tue, 13 Oct 2020 19:55:39 -0400 (EDT) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id C005A180AD807 for ; Tue, 13 Oct 2020 23:55:38 +0000 (UTC) X-FDA: 77368561956.23.game77_28087aa27207 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin23.hostedemail.com (Postfix) with ESMTP id 3372337604 for ; Tue, 13 Oct 2020 23:55:38 +0000 (UTC) X-Spam-Summary: 1,0,0,ddaaa0525fc473ce,d41d8cd98f00b204,akpm@linux-foundation.org,,RULES_HIT:41:355:379:800:960:967:973:988:989:1260:1263:1345:1359:1381:1431:1437:1534:1543:1711:1730:1747:1777:1792:2393:2525:2559:2563:2682:2685:2689:2859:2902:2933:2937:2939:2942:2945:2947:2951:2954:3022:3138:3139:3140:3141:3142:3355:3865:3866:3867:3868:3870:3871:3872:3874:3934:3936:3938:3941:3944:3947:3950:3953:3956:3959:4321:5007:6261:6653:6737:7514:7576:7903:8599:8784:9025:9545:10004:10913:11026:11473:11658:11914:12043:12048:12291:12295:12296:12297:12517:12519:12555:12679:12683:12783:12986:13146:13230:13846:14096:14181:14721:14849:21080:21094:21323:21451:21627:21939:30034:30045:30054:30064,0,RBL:198.145.29.99:@linux-foundation.org:.lbl8.mailshell.net-64.100.201.201 62.2.0.100;04y86fdsj5zjz67g74ygrh66obuq5ycpau4f5wp5ogtxmghhnd4ti1gosq3ymp7.4ajhbeh9qxoa91x6miwwbaxc8gc8mawhfiw5855y914i1c5ca3976px6hesjw45.w-lbl8.mailshell.net-223.238.255.100,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,Domai nCache:0 X-HE-Tag: game77_28087aa27207 X-Filterd-Recvd-Size: 4697 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf16.hostedemail.com (Postfix) with ESMTP for ; Tue, 13 Oct 2020 23:55:37 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 03DF622202; Tue, 13 Oct 2020 23:55:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602633336; bh=Q94IJZFH4v9ilxriS46pAfHHxIoz4laDZB77Dn4xDNo=; h=Date:From:To:Subject:In-Reply-To:From; b=CMP9ERJL2j7dbd29auYNOtSbdii3fbCMUKbc44phNv0bZhuTXZE0wWVX7DQab2Vbv JirlX/Z+yeheN+Hyqxbuiv+3MPP+kSO94X+HS+m4KrwaSvYhQQouI9a00rAAGdYH57 7z2fHT8i+JN0jy5YazudYyE2t7t5nj+mIdeN4DcA= Date: Tue, 13 Oct 2020 16:55:35 -0700 From: Andrew Morton To: akpm@linux-foundation.org, bhe@redhat.com, cai@lca.pw, david@redhat.com, jasowang@redhat.com, linux-mm@kvack.org, mhocko@suse.com, mike.kravetz@oracle.com, mm-commits@vger.kernel.org, mst@redhat.com, pankaj.gupta.linux@gmail.com, rppt@linux.ibm.com, torvalds@linux-foundation.org Subject: [patch 130/181] mm: document semantics of ZONE_MOVABLE Message-ID: <20201013235535.f2U9783nk%akpm@linux-foundation.org> In-Reply-To: <20201013164658.3bfd96cc224d8923e66a9f4e@linux-foundation.org> User-Agent: s-nail v14.8.16 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: From: David Hildenbrand Subject: mm: document semantics of ZONE_MOVABLE Let's document what ZONE_MOVABLE means, how it's used, and which special cases we have regarding unmovable pages (memory offlining vs. migration / allocations). Link: http://lkml.kernel.org/r/20200816125333.7434-7-david@redhat.com Signed-off-by: David Hildenbrand Acked-by: Mike Rapoport Cc: Michal Hocko Cc: Michael S. Tsirkin Cc: Mike Kravetz Cc: Pankaj Gupta Cc: Baoquan He Cc: Jason Wang Cc: Qian Cai Signed-off-by: Andrew Morton --- include/linux/mmzone.h | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) --- a/include/linux/mmzone.h~mm-document-semantics-of-zone_movable +++ a/include/linux/mmzone.h @@ -396,6 +396,41 @@ enum zone_type { */ ZONE_HIGHMEM, #endif + /* + * ZONE_MOVABLE is similar to ZONE_NORMAL, except that it contains + * movable pages with few exceptional cases described below. Main use + * cases for ZONE_MOVABLE are to make memory offlining/unplug more + * likely to succeed, and to locally limit unmovable allocations - e.g., + * to increase the number of THP/huge pages. Notable special cases are: + * + * 1. Pinned pages: (long-term) pinning of movable pages might + * essentially turn such pages unmovable. Memory offlining might + * retry a long time. + * 2. memblock allocations: kernelcore/movablecore setups might create + * situations where ZONE_MOVABLE contains unmovable allocations + * after boot. Memory offlining and allocations fail early. + * 3. Memory holes: kernelcore/movablecore setups might create very rare + * situations where ZONE_MOVABLE contains memory holes after boot, + * for example, if we have sections that are only partially + * populated. Memory offlining and allocations fail early. + * 4. PG_hwpoison pages: while poisoned pages can be skipped during + * memory offlining, such pages cannot be allocated. + * 5. Unmovable PG_offline pages: in paravirtualized environments, + * hotplugged memory blocks might only partially be managed by the + * buddy (e.g., via XEN-balloon, Hyper-V balloon, virtio-mem). The + * parts not manged by the buddy are unmovable PG_offline pages. In + * some cases (virtio-mem), such pages can be skipped during + * memory offlining, however, cannot be moved/allocated. These + * techniques might use alloc_contig_range() to hide previously + * exposed pages from the buddy again (e.g., to implement some sort + * of memory unplug in virtio-mem). + * + * In general, no unmovable allocations that degrade memory offlining + * should end up in ZONE_MOVABLE. Allocators (like alloc_contig_range()) + * have to expect that migrating pages in ZONE_MOVABLE can fail (even + * if has_unmovable_pages() states that there are no unmovable pages, + * there can be false negatives). + */ ZONE_MOVABLE, #ifdef CONFIG_ZONE_DEVICE ZONE_DEVICE,