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 138BFC7EE2E for ; Mon, 12 Jun 2023 09:52:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229841AbjFLJws (ORCPT ); Mon, 12 Jun 2023 05:52:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33052 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229729AbjFLJv6 (ORCPT ); Mon, 12 Jun 2023 05:51:58 -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 9B2EC44B4 for ; Mon, 12 Jun 2023 02:36:28 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R171e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046056;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VkwIOnf_1686562584; Received: from 30.97.48.52(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VkwIOnf_1686562584) by smtp.aliyun-inc.com; Mon, 12 Jun 2023 17:36:25 +0800 Message-ID: Date: Mon, 12 Jun 2023 17:36:43 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.11.2 Subject: Re: [PATCH] mm: compaction: skip memory hole rapidly when isolating migratable pages To: "Huang, Ying" Cc: akpm@linux-foundation.org, mgorman@techsingularity.net, vbabka@suse.cz, david@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <8cc668b77c8eb2fa78058b3d81386ebed9c5a9cd.1686294549.git.baolin.wang@linux.alibaba.com> <87sfax6v7c.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Baolin Wang In-Reply-To: <87sfax6v7c.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 6/12/2023 2:39 PM, Huang, Ying wrote: > Baolin Wang writes: > >> On some machines, the normal zone can have a large memory hole like >> below memory layout, and we can see the range from 0x100000000 to >> 0x1800000000 is a hole. So when isolating some migratable pages, the >> scanner can meet the hole and it will take more time to skip the large >> hole. From my measurement, I can see the isolation scanner will take >> 80us ~ 100us to skip the large hole [0x100000000 - 0x1800000000]. >> >> So adding a new helper to fast search next online memory section >> to skip the large hole can help to find next suitable pageblock >> efficiently. With this patch, I can see the large hole scanning only >> takes < 1us. >> >> [ 0.000000] Zone ranges: >> [ 0.000000] DMA [mem 0x0000000040000000-0x00000000ffffffff] >> [ 0.000000] DMA32 empty >> [ 0.000000] Normal [mem 0x0000000100000000-0x0000001fa7ffffff] >> [ 0.000000] Movable zone start for each node >> [ 0.000000] Early memory node ranges >> [ 0.000000] node 0: [mem 0x0000000040000000-0x0000000fffffffff] >> [ 0.000000] node 0: [mem 0x0000001800000000-0x0000001fa3c7ffff] >> [ 0.000000] node 0: [mem 0x0000001fa3c80000-0x0000001fa3ffffff] >> [ 0.000000] node 0: [mem 0x0000001fa4000000-0x0000001fa402ffff] >> [ 0.000000] node 0: [mem 0x0000001fa4030000-0x0000001fa40effff] >> [ 0.000000] node 0: [mem 0x0000001fa40f0000-0x0000001fa73cffff] >> [ 0.000000] node 0: [mem 0x0000001fa73d0000-0x0000001fa745ffff] >> [ 0.000000] node 0: [mem 0x0000001fa7460000-0x0000001fa746ffff] >> [ 0.000000] node 0: [mem 0x0000001fa7470000-0x0000001fa758ffff] >> [ 0.000000] node 0: [mem 0x0000001fa7590000-0x0000001fa7ffffff] >> >> Signed-off-by: Baolin Wang >> --- >> include/linux/mmzone.h | 10 ++++++++++ >> mm/compaction.c | 23 ++++++++++++++++++++++- >> 2 files changed, 32 insertions(+), 1 deletion(-) >> >> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h >> index 5a7ada0413da..87e6c535d895 100644 >> --- a/include/linux/mmzone.h >> +++ b/include/linux/mmzone.h >> @@ -2000,6 +2000,16 @@ static inline unsigned long next_present_section_nr(unsigned long section_nr) >> return -1; >> } >> >> +static inline unsigned long next_online_section_nr(unsigned long section_nr) >> +{ >> + while (++section_nr <= __highest_present_section_nr) { >> + if (online_section_nr(section_nr)) >> + return section_nr; >> + } >> + >> + return -1UL; >> +} >> + >> /* >> * These are _only_ used during initialisation, therefore they >> * can use __initdata ... They could have names to indicate >> diff --git a/mm/compaction.c b/mm/compaction.c >> index 3398ef3a55fe..3a55fdd20c49 100644 >> --- a/mm/compaction.c >> +++ b/mm/compaction.c >> @@ -229,6 +229,21 @@ static void reset_cached_positions(struct zone *zone) >> pageblock_start_pfn(zone_end_pfn(zone) - 1); >> } >> >> +static unsigned long skip_hole_pageblock(unsigned long start_pfn) >> +{ >> + unsigned long next_online_nr; >> + unsigned long start_nr = pfn_to_section_nr(start_pfn); >> + >> + if (online_section_nr(start_nr)) >> + return -1UL; > > Define a macro for the maigic "-1UL"? Which is used for multiple times > in the patch. I am struggling to find a readable macro for these '-1UL', since the '-1UL' in next_online_section_nr() indicates that it can not find an online section. However the '-1' in skip_hole_pageblock() indicates that it can not find an online pfn. So after more thinking, I will change to return 'NR_MEM_SECTIONS' if can not find next online section in next_online_section_nr(). And in skip_hole_pageblock(), I will change to return 0 if can not find next online pfn. What do you think? static unsigned long skip_hole_pageblock(unsigned long start_pfn) { unsigned long next_online_nr; unsigned long start_nr = pfn_to_section_nr(start_pfn); if (online_section_nr(start_nr)) return 0; next_online_nr = next_online_section_nr(start_nr); if (next_online_nr < NR_MEM_SECTIONS) return section_nr_to_pfn(next_online_nr); return 0; } >> + >> + next_online_nr = next_online_section_nr(start_nr); >> + if (next_online_nr != -1UL) >> + return section_nr_to_pfn(next_online_nr); >> + >> + return -1UL; >> +} >> + >> /* >> * Compound pages of >= pageblock_order should consistently be skipped until >> * released. It is always pointless to compact pages of such order (if they are >> @@ -1991,8 +2006,14 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc) >> >> page = pageblock_pfn_to_page(block_start_pfn, >> block_end_pfn, cc->zone); >> - if (!page) >> + if (!page) { >> + unsigned long next_pfn; >> + >> + next_pfn = skip_hole_pageblock(block_start_pfn); >> + if (next_pfn != -1UL) >> + block_end_pfn = next_pfn; >> continue; >> + } >> >> /* >> * If isolation recently failed, do not retry. Only check the > > Do we need to do similar change in isolate_freepages()? Yes, it's in my todo list with some measurement data. Thanks for your comments.