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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 618C0C71153 for ; Thu, 24 Aug 2023 06:27:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240070AbjHXG1E (ORCPT ); Thu, 24 Aug 2023 02:27:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47298 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240051AbjHXG0b (ORCPT ); Thu, 24 Aug 2023 02:26:31 -0400 Received: from out30-100.freemail.mail.aliyun.com (out30-100.freemail.mail.aliyun.com [115.124.30.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A3EFA137 for ; Wed, 23 Aug 2023 23:26:28 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R411e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045192;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VqSeeXB_1692858383; Received: from 30.97.48.68(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VqSeeXB_1692858383) by smtp.aliyun-inc.com; Thu, 24 Aug 2023 14:26:24 +0800 Message-ID: Date: Thu, 24 Aug 2023 14:26:25 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.14.0 Subject: Re: [PATCH v2 0/4] Extend migrate_misplaced_page() to support batch migration To: "Huang, Ying" Cc: akpm@linux-foundation.org, mgorman@techsingularity.net, shy828301@gmail.com, david@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <87pm3fbxos.fsf@yhuang6-desk2.ccr.corp.intel.com> <87zg2h9h5c.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Baolin Wang In-Reply-To: <87zg2h9h5c.fsf@yhuang6-desk2.ccr.corp.intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/24/2023 12:51 PM, Huang, Ying wrote: > Baolin Wang writes: > >> On 8/22/2023 10:47 AM, Huang, Ying wrote: >>> Baolin Wang writes: >>> >>>> Hi, >>>> >>>> Currently, on our ARM servers with NUMA enabled, we found the cross-die latency >>>> is a little larger that will significantly impact the workload's performance. >>>> So on ARM servers we will rely on the NUMA balancing to avoid the cross-die >>>> accessing. And I posted a patchset[1] to support speculative numa fault to >>>> improve the NUMA balancing's performance according to the principle of data >>>> locality. Moreover, thanks to Huang Ying's patchset[2], which introduced batch >>>> migration as a way to reduce the cost of TLB flush, and it will also benefit >>>> the migration of multiple pages all at once during NUMA balancing. >>>> >>>> So we plan to continue to support batch migration in do_numa_page() to improve >>>> the NUMA balancing's performance, but before adding complicated batch migration >>>> algorithm for NUMA balancing, some cleanup and preparation work need to do firstly, >>>> which are done in this patch set. In short, this patchset extends the >>>> migrate_misplaced_page() interface to support batch migration, and no functional >>>> changes intended. >>>> >>>> In addition, these cleanup can also benefit the compound page's NUMA balancing, >>>> which was discussed in previous thread[3]. IIUC, for the compound page's NUMA >>>> balancing, it is possible that partial pages were successfully migrated, so it is >>>> necessary to return the number of pages that were successfully migrated from >>>> migrate_misplaced_page(). >>> But I don't find the return number is used except as bool now. >> >> As I said above, this is a preparation for batch migration and >> compound page NUMA balancing in future. >> >> In addition, after looking into the THP' NUMA migration, I found this >> change is necessary for THP migration. Since it is possible that >> partial subpages were successfully migrated if the THP is split, so >> below THP numa fault statistics is not always correct: >> >> if (page_nid != NUMA_NO_NODE) >> task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, >> flags); >> >> I will try to fix this in next version. > > IIUC, THP will not be split for NUMA balancing. Please check the > nosplit logic in migrate_pages_batch(). > > bool nosplit = (reason == MR_NUMA_MISPLACED); Yes, I overlooked this. Thanks for reminding. > >>> Per my understanding, I still don't find much value of the changes >>> except as preparation for batch migration in NUMA balancing. So I still >> >> IMO, only patch 3 is just a preparation for batch migration, but other >> patches are some cleanups for migrate_misplaced_page(). I can drop the >> preparation patches in this series and revise the commit message. >> >>> think it's better to wait for the whole series. Where we can check why >>> these changes are necessary for batch migration. And I think that you >>> will provide some number to justify the batch migration, including pros >>> and cons. >>> -- >>> Best Regards, >>> Huang, Ying >>> >>>> This series is based on the latest mm-unstable(d226b59b30cc). >>>> >>>> [1] https://lore.kernel.org/lkml/cover.1639306956.git.baolin.wang@linux.alibaba.com/t/#mc45929849b5d0e29b5fdd9d50425f8e95b8f2563 >>>> [2] https://lore.kernel.org/all/20230213123444.155149-1-ying.huang@intel.com/T/#u >>>> [3] https://lore.kernel.org/all/f8d47176-03a8-99bf-a813-b5942830fd73@arm.com/ >>>> >>>> Changes from v1: >>>> - Move page validation into a new function suggested by Huang Ying. >>>> - Change numamigrate_isolate_page() to boolean type. >>>> - Update some commit message. >>>> >>>> Baolin Wang (4): >>>> mm: migrate: factor out migration validation into >>>> numa_page_can_migrate() >>>> mm: migrate: move the numamigrate_isolate_page() into do_numa_page() >>>> mm: migrate: change migrate_misplaced_page() to support multiple pages >>>> migration >>>> mm: migrate: change to return the number of pages migrated >>>> successfully >>>> >>>> include/linux/migrate.h | 15 +++++++--- >>>> mm/huge_memory.c | 23 +++++++++++++-- >>>> mm/internal.h | 1 + >>>> mm/memory.c | 43 ++++++++++++++++++++++++++- >>>> mm/migrate.c | 64 +++++++++-------------------------------- >>>> 5 files changed, 88 insertions(+), 58 deletions(-)