From patchwork Wed Mar 17 11:12:46 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oscar Salvador X-Patchwork-Id: 12145553 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=-11.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_GIT autolearn=ham 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 DEF5FC433E9 for ; Wed, 17 Mar 2021 11:13:07 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9670A64F67 for ; Wed, 17 Mar 2021 11:13:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9670A64F67 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1849F6B006E; Wed, 17 Mar 2021 07:13:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0516D6B0071; Wed, 17 Mar 2021 07:13:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D653D6B0071; Wed, 17 Mar 2021 07:13:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0246.hostedemail.com [216.40.44.246]) by kanga.kvack.org (Postfix) with ESMTP id B8C6D6B0070 for ; Wed, 17 Mar 2021 07:13:05 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 6A323181AF5CC for ; Wed, 17 Mar 2021 11:13:05 +0000 (UTC) X-FDA: 77929104330.28.45B74F2 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf04.hostedemail.com (Postfix) with ESMTP id C93343C2 for ; Wed, 17 Mar 2021 11:13:04 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 5EFBBAC1F; Wed, 17 Mar 2021 11:13:03 +0000 (UTC) From: Oscar Salvador To: Andrew Morton Cc: Vlastimil Babka , David Hildenbrand , Michal Hocko , Muchun Song , Mike Kravetz , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oscar Salvador Subject: [PATCH v5 0/5] Make alloc_contig_range handle Hugetlb pages Date: Wed, 17 Mar 2021 12:12:46 +0100 Message-Id: <20210317111251.17808-1-osalvador@suse.de> X-Mailer: git-send-email 2.13.7 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C93343C2 X-Stat-Signature: 9n41pne55uudfxnjur9uoam4qnu8e4zf Received-SPF: none (suse.de>: No applicable sender policy available) receiver=imf04; identity=mailfrom; envelope-from=""; helo=mx2.suse.de; client-ip=195.135.220.15 X-HE-DKIM-Result: none/none X-HE-Tag: 1615979584-120989 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: v4->v5: - Collect Acked-by and Reviewed-by from David and Vlastimil - Drop racy checks in pfn_range_valid_contig (David) - Rebased on top of 5.12-rc3 v3 -> v4: - Addressed some feedback from David and Michal - Make more clear what hugetlb_lock protects in isolate_or_dissolve_huge_page - Start reporting proper error codes from isolate_migratepages_{range,block} - Bail out earlier in __alloc_contig_migrate_range on -ENOMEM - Addressed internal feedback from Vastlimil wrt. compaction code changes v2 -> v3: - Drop usage of high-level generic helpers in favour of low-level approach (per Michal) - Check for the page to be marked as PageHugeFreed - Add a one-time retry in case someone grabbed the free huge page from under us v1 -> v2: - Adressed feedback by Michal - Restrict the allocation to a node with __GFP_THISNODE - Drop PageHuge check in alloc_and_dissolve_huge_page - Re-order comments in isolate_or_dissolve_huge_page - Extend comment in isolate_migratepages_block - Place put_page right after we got the page, otherwise dissolve_free_huge_page will fail RFC -> v1: - Drop RFC - Addressed feedback from David and Mike - Fence off gigantic pages as there is a cyclic dependency between them and alloc_contig_range - Re-organize the code to make race-window smaller and to put all details in hugetlb code - Drop nodemask initialization. First a node will be tried and then we will back to other nodes containing memory (N_MEMORY). Details in patch#1's changelog - Count new page as surplus in case we failed to dissolve the old page and the new one. Details in patch#1. Cover letter: alloc_contig_range lacks the hability for handling HugeTLB pages. This can be problematic for some users, e.g: CMA and virtio-mem, where those users will fail the call if alloc_contig_range ever sees a HugeTLB page, even when those pages lay in ZONE_MOVABLE and are free. That problem can be easily solved by replacing the page in the free hugepage pool. In-use HugeTLB are no exception though, as those can be isolated and migrated as any other LRU or Movable page. This patchset aims for improving alloc_contig_range->isolate_migratepages_block, so HugeTLB pages can be recognized and handled. Since we also need to start reporting errors down the chain (e.g: -ENOMEM due to not be able to allocate a new hugetlb page), isolate_migratepages_{range,block} interfaces need to change to start reporting error codes instead of the pfn == 0 vs pfn != 0 scheme it is using right now. From now on, isolate_migratepages_block will not return the next pfn to be scanned anymore, but -EINTR, -ENOMEM or 0, so we the next pfn to be scanned will be recorded in cc->migrate_pfn field (as it is already done in isolate_migratepages_range()). Below is an insight from David (thanks), where the problem can clearly be seen: "Start a VM with 4G. Hotplug 1G via virtio-mem and online it to ZONE_MOVABLE. Allocate 512 huge pages. [root@localhost ~]# cat /proc/meminfo MemTotal: 5061512 kB MemFree: 3319396 kB MemAvailable: 3457144 kB ... HugePages_Total: 512 HugePages_Free: 512 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB The huge pages get partially allocate from ZONE_MOVABLE. Try unplugging 1G via virtio-mem (remember, all ZONE_MOVABLE). Inside the guest: [ 180.058992] alloc_contig_range: [1b8000, 1c0000) PFNs busy [ 180.060531] alloc_contig_range: [1b8000, 1c0000) PFNs busy [ 180.061972] alloc_contig_range: [1b8000, 1c0000) PFNs busy [ 180.063413] alloc_contig_range: [1b8000, 1c0000) PFNs busy [ 180.064838] alloc_contig_range: [1b8000, 1c0000) PFNs busy [ 180.065848] alloc_contig_range: [1bfc00, 1c0000) PFNs busy [ 180.066794] alloc_contig_range: [1bfc00, 1c0000) PFNs busy [ 180.067738] alloc_contig_range: [1bfc00, 1c0000) PFNs busy [ 180.068669] alloc_contig_range: [1bfc00, 1c0000) PFNs busy [ 180.069598] alloc_contig_range: [1bfc00, 1c0000) PFNs busy" And then with this patchset running: "Same experiment with ZONE_MOVABLE: a) Free huge pages: all memory can get unplugged again. b) Allocated/populated but idle huge pages: all memory can get unplugged again. c) Allocated/populated but all 512 huge pages are read/written in a loop: all memory can get unplugged again, but I get a single [ 121.192345] alloc_contig_range: [180000, 188000) PFNs busy Most probably because it happened to try migrating a huge page while it was busy. As virtio-mem retries on ZONE_MOVABLE a couple of times, it can deal with this temporary failure. Last but not least, I did something extreme: # cat /proc/meminfo MemTotal: 5061568 kB MemFree: 186560 kB MemAvailable: 354524 kB ... HugePages_Total: 2048 HugePages_Free: 2048 HugePages_Rsvd: 0 HugePages_Surp: 0 Triggering unplug would require to dissolve+alloc - which now fails when trying to allocate an additional ~512 huge pages (1G). As expected, I can properly see memory unplug not fully succeeding. + I get a fairly continuous stream of [ 226.611584] alloc_contig_range: [19f400, 19f800) PFNs busy ... But more importantly, the hugepage count remains stable, as configured by the admin (me): HugePages_Total: 2048 HugePages_Free: 2048 HugePages_Rsvd: 0 HugePages_Surp: 0" Oscar Salvador (5): mm,page_alloc: Bail out earlier on -ENOMEM in alloc_contig_migrate_range mm,compaction: Let isolate_migratepages_{range,block} return error codes mm: Make alloc_contig_range handle free hugetlb pages mm: Make alloc_contig_range handle in-use hugetlb pages mm,page_alloc: Drop unnecessary checks from pfn_range_valid_contig include/linux/hugetlb.h | 7 +++ mm/compaction.c | 89 ++++++++++++++++++++++++---------- mm/hugetlb.c | 125 +++++++++++++++++++++++++++++++++++++++++++++++- mm/internal.h | 2 +- mm/page_alloc.c | 21 ++++---- mm/vmscan.c | 5 +- 6 files changed, 209 insertions(+), 40 deletions(-)