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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C41E9C433EF for ; Sun, 7 Nov 2021 08:57:50 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6FE52613A6 for ; Sun, 7 Nov 2021 08:57:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 6FE52613A6 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 671D66B00D7; Sun, 7 Nov 2021 03:57:44 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4B88D6B00DB; Sun, 7 Nov 2021 03:57:44 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0F0106B00D7; Sun, 7 Nov 2021 03:57:44 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0021.hostedemail.com [216.40.44.21]) by kanga.kvack.org (Postfix) with ESMTP id D61156B00D5 for ; Sun, 7 Nov 2021 03:57:43 -0500 (EST) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 79ABE82499A8 for ; Sun, 7 Nov 2021 08:57:43 +0000 (UTC) X-FDA: 78781531206.24.A0A29FB Received: from out30-43.freemail.mail.aliyun.com (out30-43.freemail.mail.aliyun.com [115.124.30.43]) by imf16.hostedemail.com (Postfix) with ESMTP id 20251F0000AC for ; Sun, 7 Nov 2021 08:57:32 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R201e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0UvOEkA._1636275457; Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0UvOEkA._1636275457) by smtp.aliyun-inc.com(127.0.0.1); Sun, 07 Nov 2021 16:57:37 +0800 From: Baolin Wang To: akpm@linux-foundation.org Cc: ziy@nvidia.com, shy828301@gmail.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/3] mm: migrate: Fix the return value of migrate_pages() Date: Sun, 7 Nov 2021 16:57:25 +0800 Message-Id: <6486fabc3e8c66ff613e150af25e89b3147977a6.1636275127.git.baolin.wang@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: References: In-Reply-To: References: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 20251F0000AC X-Stat-Signature: yt4tzx4dw6gfo3dwohb689ucaxk7euzk Authentication-Results: imf16.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=alibaba.com; spf=pass (imf16.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.43 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com X-HE-Tag: 1636275452-83822 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: As Zi Yan pointed out, the syscall move_pages() can return a non-migrated number larger than the number of pages the users tried to migrate, when a THP page is failed to migrate. This is confusing for users. Since other migration scenarios do not care about the actual non-migrated number of pages except the memory compaction migration which will fix in following patch. Thus we can change the return value to return the number of {normal page, THP, hugetlb} instead to avoid this issue, and the number of THP splits will be considered as the number of non-migrated THP, no matter how many subpages of the THP are migrated successfully. Meanwhile we should still keep the migration counters using the number of normal pages. Co-developed-by: Zi Yan Signed-off-by: Zi Yan Signed-off-by: Baolin Wang --- mm/migrate.c | 63 +++++++++++++++++++++++++++++++++++++++++++++--------------- 1 file changed, 47 insertions(+), 16 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index a11e948..9aafdab 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1428,7 +1428,7 @@ static inline int try_split_thp(struct page *page, struct page **page2, * @mode: The migration mode that specifies the constraints for * page migration, if any. * @reason: The reason for page migration. - * @ret_succeeded: Set to the number of pages migrated successfully if + * @ret_succeeded: Set to the number of normal pages migrated successfully if * the caller passes a non-NULL pointer. * * The function returns after 10 attempts or if no pages are movable any more @@ -1436,7 +1436,9 @@ static inline int try_split_thp(struct page *page, struct page **page2, * It is caller's responsibility to call putback_movable_pages() to return pages * to the LRU or free list only if ret != 0. * - * Returns the number of pages that were not migrated, or an error code. + * Returns the number of {normal page, THP} that were not migrated, or an error code. + * The number of THP splits will be considered as the number of non-migrated THP, + * no matter how many subpages of the THP are migrated successfully. */ int migrate_pages(struct list_head *from, new_page_t get_new_page, free_page_t put_new_page, unsigned long private, @@ -1445,6 +1447,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, int retry = 1; int thp_retry = 1; int nr_failed = 0; + int nr_failed_pages = 0; int nr_succeeded = 0; int nr_thp_succeeded = 0; int nr_thp_failed = 0; @@ -1456,13 +1459,16 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, int swapwrite = current->flags & PF_SWAPWRITE; int rc, nr_subpages; LIST_HEAD(ret_pages); + LIST_HEAD(thp_split_pages); bool nosplit = (reason == MR_NUMA_MISPLACED); + bool no_subpage_counting = false; trace_mm_migrate_pages_start(mode, reason); if (!swapwrite) current->flags |= PF_SWAPWRITE; +thp_subpage_migration: for (pass = 0; pass < 10 && (retry || thp_retry); pass++) { retry = 0; thp_retry = 0; @@ -1511,18 +1517,20 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, case -ENOSYS: /* THP migration is unsupported */ if (is_thp) { - if (!try_split_thp(page, &page2, from)) { + nr_thp_failed++; + if (!try_split_thp(page, &page2, &thp_split_pages)) { nr_thp_split++; goto retry; } - nr_thp_failed++; - nr_failed += nr_subpages; + nr_failed_pages += nr_subpages; break; } /* Hugetlb migration is unsupported */ - nr_failed++; + if (!no_subpage_counting) + nr_failed++; + nr_failed_pages++; break; case -ENOMEM: /* @@ -1531,16 +1539,19 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, * THP NUMA faulting doesn't split THP to retry. */ if (is_thp && !nosplit) { - if (!try_split_thp(page, &page2, from)) { + nr_thp_failed++; + if (!try_split_thp(page, &page2, &thp_split_pages)) { nr_thp_split++; goto retry; } - nr_thp_failed++; - nr_failed += nr_subpages; + nr_failed_pages += nr_subpages; goto out; } - nr_failed++; + + if (!no_subpage_counting) + nr_failed++; + nr_failed_pages++; goto out; case -EAGAIN: if (is_thp) { @@ -1566,17 +1577,37 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, */ if (is_thp) { nr_thp_failed++; - nr_failed += nr_subpages; + nr_failed_pages += nr_subpages; break; } - nr_failed++; + + if (!no_subpage_counting) + nr_failed++; + nr_failed_pages++; break; } } } - nr_failed += retry + thp_retry; + nr_failed += retry; nr_thp_failed += thp_retry; - rc = nr_failed; + /* + * Try to migrate subpages of fail-to-migrate THPs, no nr_failed + * counting in this round, since all subpages of a THP is counted + * as 1 failure in the first round. + */ + if (!list_empty(&thp_split_pages)) { + /* + * Move non-migrated pages (after 10 retries) to ret_pages + * to avoid migrating them again. + */ + list_splice_init(from, &ret_pages); + list_splice_init(&thp_split_pages, from); + no_subpage_counting = true; + retry = 1; + goto thp_subpage_migration; + } + + rc = nr_failed + nr_thp_failed; out: /* * Put the permanent failure page back to migration list, they @@ -1585,11 +1616,11 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, list_splice(&ret_pages, from); count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded); - count_vm_events(PGMIGRATE_FAIL, nr_failed); + count_vm_events(PGMIGRATE_FAIL, nr_failed_pages); count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded); count_vm_events(THP_MIGRATION_FAIL, nr_thp_failed); count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split); - trace_mm_migrate_pages(nr_succeeded, nr_failed, nr_thp_succeeded, + trace_mm_migrate_pages(nr_succeeded, nr_failed_pages, nr_thp_succeeded, nr_thp_failed, nr_thp_split, mode, reason); if (!swapwrite) -- 1.8.3.1