From nobody Thu Dec 18 15:31:49 2025 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 586A5CDB47E for ; Wed, 18 Oct 2023 13:04:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230516AbjJRNEo (ORCPT ); Wed, 18 Oct 2023 09:04:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36812 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230296AbjJRNEn (ORCPT ); Wed, 18 Oct 2023 09:04:43 -0400 Received: from out30-113.freemail.mail.aliyun.com (out30-113.freemail.mail.aliyun.com [115.124.30.113]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7777E106 for ; Wed, 18 Oct 2023 06:04:39 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046059;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0VuR0XGI_1697634275; Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VuR0XGI_1697634275) by smtp.aliyun-inc.com; Wed, 18 Oct 2023 21:04:36 +0800 From: Baolin Wang To: akpm@linux-foundation.org Cc: mgorman@techsingularity.net, hughd@google.com, vbabka@suse.cz, ying.huang@intel.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH] mm: migrate: record the mlocked page status to remove unnecessary lru drain Date: Wed, 18 Oct 2023 21:04:32 +0800 Message-Id: <64899ad0bb78cde88b52abed1a5a5abbc9919998.1697632761.git.baolin.wang@linux.alibaba.com> X-Mailer: git-send-email 2.39.3 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When doing compaction, I found the lru_add_drain() is an obvious hotspot when migrating pages. The distribution of this hotspot is as follows: - 18.75% compact_zone - 17.39% migrate_pages - 13.79% migrate_pages_batch - 11.66% migrate_folio_move - 7.02% lru_add_drain + 7.02% lru_add_drain_cpu + 3.00% move_to_new_folio 1.23% rmap_walk + 1.92% migrate_folio_unmap + 3.20% migrate_pages_sync + 0.90% isolate_migratepages The lru_add_drain() was added by commit c3096e6782b7 ("mm/migrate: __unmap_and_move() push good newpage to LRU") to drain the newpage to LRU immediately, to help to build up the correct newpage->mlock_count in remove_migration_ptes() for mlocked pages. However, if there are no mlocked pages are migrating, then we can avoid this lru drain operation, especailly for the heavy concurrent scenarios. So we can record the source pages' mlocked status in migrate_folio_unmap(), and only drain the lru list when the mlocked status is set in migrate_folio= _move(). In addition, the page was already isolated from lru when migrating, so we check the mlocked status is stable by folio_test_mlocked() in migrate_folio= _unmap(). After this patch, I can see the hotpot of the lru_add_drain() is gone: - 9.41% migrate_pages_batch - 6.15% migrate_folio_move - 3.64% move_to_new_folio + 1.80% migrate_folio_extra + 1.70% buffer_migrate_folio + 1.41% rmap_walk + 0.62% folio_add_lru + 3.07% migrate_folio_unmap Meanwhile, the compaction latency shows some improvements when running thpscale: base patched Amean fault-both-1 1131.22 ( 0.00%) 1112.55 * 1.65%* Amean fault-both-3 2489.75 ( 0.00%) 2324.15 * 6.65%* Amean fault-both-5 3257.37 ( 0.00%) 3183.18 * 2.28%* Amean fault-both-7 4257.99 ( 0.00%) 4079.04 * 4.20%* Amean fault-both-12 6614.02 ( 0.00%) 6075.60 * 8.14%* Amean fault-both-18 10607.78 ( 0.00%) 8978.86 * 15.36%* Amean fault-both-24 14911.65 ( 0.00%) 11619.55 * 22.08%* Amean fault-both-30 14954.67 ( 0.00%) 14925.66 * 0.19%* Amean fault-both-32 16654.87 ( 0.00%) 15580.31 * 6.45%* Signed-off-by: Baolin Wang --- mm/migrate.c | 50 ++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 38 insertions(+), 12 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index 4caf405b6504..32c96f89710f 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1027,22 +1027,32 @@ union migration_ptr { struct anon_vma *anon_vma; struct address_space *mapping; }; + +enum { + PAGE_WAS_MAPPED =3D 1 << 0, + PAGE_WAS_MLOCKED =3D 1 << 1, +}; + static void __migrate_folio_record(struct folio *dst, - unsigned long page_was_mapped, + unsigned long page_flags, struct anon_vma *anon_vma) { union migration_ptr ptr =3D { .anon_vma =3D anon_vma }; dst->mapping =3D ptr.mapping; - dst->private =3D (void *)page_was_mapped; + dst->private =3D (void *)page_flags; } =20 static void __migrate_folio_extract(struct folio *dst, int *page_was_mappedp, + int *page_was_mlocked, struct anon_vma **anon_vmap) { union migration_ptr ptr =3D { .mapping =3D dst->mapping }; + unsigned long page_flags =3D (unsigned long)dst->private; + *anon_vmap =3D ptr.anon_vma; - *page_was_mappedp =3D (unsigned long)dst->private; + *page_was_mappedp =3D page_flags & PAGE_WAS_MAPPED ? 1 : 0; + *page_was_mlocked =3D page_flags & PAGE_WAS_MLOCKED ? 1 : 0; dst->mapping =3D NULL; dst->private =3D NULL; } @@ -1103,7 +1113,7 @@ static int migrate_folio_unmap(new_folio_t get_new_fo= lio, { struct folio *dst; int rc =3D -EAGAIN; - int page_was_mapped =3D 0; + int page_was_mapped =3D 0, page_was_mlocked =3D 0; struct anon_vma *anon_vma =3D NULL; bool is_lru =3D !__folio_test_movable(src); bool locked =3D false; @@ -1157,6 +1167,7 @@ static int migrate_folio_unmap(new_folio_t get_new_fo= lio, folio_lock(src); } locked =3D true; + page_was_mlocked =3D folio_test_mlocked(src); =20 if (folio_test_writeback(src)) { /* @@ -1206,7 +1217,7 @@ static int migrate_folio_unmap(new_folio_t get_new_fo= lio, dst_locked =3D true; =20 if (unlikely(!is_lru)) { - __migrate_folio_record(dst, page_was_mapped, anon_vma); + __migrate_folio_record(dst, 0, anon_vma); return MIGRATEPAGE_UNMAP; } =20 @@ -1236,7 +1247,13 @@ static int migrate_folio_unmap(new_folio_t get_new_f= olio, } =20 if (!folio_mapped(src)) { - __migrate_folio_record(dst, page_was_mapped, anon_vma); + unsigned int page_flags =3D 0; + + if (page_was_mapped) + page_flags |=3D PAGE_WAS_MAPPED; + if (page_was_mlocked) + page_flags |=3D PAGE_WAS_MLOCKED; + __migrate_folio_record(dst, page_flags, anon_vma); return MIGRATEPAGE_UNMAP; } =20 @@ -1261,12 +1278,13 @@ static int migrate_folio_move(free_folio_t put_new_= folio, unsigned long private, struct list_head *ret) { int rc; - int page_was_mapped =3D 0; + int page_was_mapped =3D 0, page_was_mlocked =3D 0; struct anon_vma *anon_vma =3D NULL; bool is_lru =3D !__folio_test_movable(src); struct list_head *prev; =20 - __migrate_folio_extract(dst, &page_was_mapped, &anon_vma); + __migrate_folio_extract(dst, &page_was_mapped, + &page_was_mlocked, &anon_vma); prev =3D dst->lru.prev; list_del(&dst->lru); =20 @@ -1287,7 +1305,7 @@ static int migrate_folio_move(free_folio_t put_new_fo= lio, unsigned long private, * isolated from the unevictable LRU: but this case is the easiest. */ folio_add_lru(dst); - if (page_was_mapped) + if (page_was_mlocked) lru_add_drain(); =20 if (page_was_mapped) @@ -1321,8 +1339,15 @@ static int migrate_folio_move(free_folio_t put_new_f= olio, unsigned long private, * right list unless we want to retry. */ if (rc =3D=3D -EAGAIN) { + unsigned int page_flags =3D 0; + + if (page_was_mapped) + page_flags |=3D PAGE_WAS_MAPPED; + if (page_was_mlocked) + page_flags |=3D PAGE_WAS_MLOCKED; + list_add(&dst->lru, prev); - __migrate_folio_record(dst, page_was_mapped, anon_vma); + __migrate_folio_record(dst, page_flags, anon_vma); return rc; } =20 @@ -1799,10 +1824,11 @@ static int migrate_pages_batch(struct list_head *fr= om, dst =3D list_first_entry(&dst_folios, struct folio, lru); dst2 =3D list_next_entry(dst, lru); list_for_each_entry_safe(folio, folio2, &unmap_folios, lru) { - int page_was_mapped =3D 0; + int page_was_mapped =3D 0, page_was_mlocked =3D 0; struct anon_vma *anon_vma =3D NULL; =20 - __migrate_folio_extract(dst, &page_was_mapped, &anon_vma); + __migrate_folio_extract(dst, &page_was_mapped, + &page_was_mlocked, &anon_vma); migrate_folio_undo_src(folio, page_was_mapped, anon_vma, true, ret_folios); list_del(&dst->lru); --=20 2.39.3