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X-IronPort-AV: E=McAfee;i="6600,9927,10866"; a="383136884" X-IronPort-AV: E=Sophos;i="6.03,233,1694761200"; d="scan'208";a="383136884" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Oct 2023 18:29:45 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10866"; a="1003568528" X-IronPort-AV: E=Sophos;i="6.03,233,1694761200"; d="scan'208";a="1003568528" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by fmsmga006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Oct 2023 18:29:42 -0700 From: "Huang, Ying" To: Zi Yan Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Zi Yan , Andrew Morton , "Matthew Wilcox (Oracle)" , David Hildenbrand , Baolin Wang Subject: Re: [PATCH v3 1/2] mm/migrate: correct nr_failed in migrate_pages_sync() In-Reply-To: <20231017163129.2025214-1-zi.yan@sent.com> (Zi Yan's message of "Tue, 17 Oct 2023 12:31:28 -0400") References: <20231017163129.2025214-1-zi.yan@sent.com> Date: Wed, 18 Oct 2023 09:27:41 +0800 Message-ID: <878r8090tu.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspam-User: X-Stat-Signature: x3mkr3c4se9cmhdjj4z5kkohqopian3z X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: D81EC1A0007 X-HE-Tag: 1697592586-722073 X-HE-Meta: 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 ErdSSrG7 uN/yyDphL6tz4wdfTw/CJhuLIswHLz/yfl9+6Zzdxj1ADPFYucaRF579adn296ptPoDDmUvsFycrOQQ4J818INeu6PVnHUDUB/9VzR1U312DpI4W3bORGImZmAqbtZkuGUX13+8bVloSF1rysAeP9avzWlBi7V9Lo8/X5cFrmYm5CWq1pVJvHuylHGkuHvvD7J1Bej8sbuB7LlO1Rwo/9L2RXOEYAUVCizXfKNG3e5iFKHlr0FJByyHYr349uFhAn9bTPv2aJeoaY9k+tQa1Ue/HU4ByNdm69dDyIdglBucYvQpbQpNHxu5Ni4VPa2nnuui4IavkT0DvrNQAHPXiAbtNFErJM1c2uqOJgmUwUuRRcPpUHq6xGZy7eybhTHe9VauMWbdoKubvIevc9Ubb0HvfLE/k7/6F/HCtZ7ZwlZj/vWyE= 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: Zi Yan writes: > From: Zi Yan > > nr_failed was missing the large folio splits from migrate_pages_batch() > and can cause a mismatch between migrate_pages() return value and the > number of not migrated pages, i.e., when the return value of > migrate_pages() is 0, there are still pages left in the from page list. > It will happen when a non-PMD THP large folio fails to migrate due to > -ENOMEM and is split successfully but not all the split pages are not > migrated, migrate_pages_batch() would return non-zero, but > astats.nr_thp_split = 0. nr_failed would be 0 and returned to the caller > of migrate_pages(), but the not migrated pages are left in the from page > list without being added back to LRU lists. > > Fix it by adding a new nr_split counter for large folio splits and adding > it to nr_failed in migrate_page_sync() after migrate_pages_batch() is > done. > > Fixes: 2ef7dbb26990 ("migrate_pages: try migrate in batch asynchronously firstly") > Signed-off-by: Zi Yan > Cc: Baolin Wang > Cc: David Hildenbrand > Cc: Huang Ying > Cc: Matthew Wilcox LGTM except a trivial issue below, not a big deal. Thanks! Reviewed-by: "Huang, Ying" > --- > mm/migrate.c | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index c602bf6dec97..fc2e70b17704 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1495,6 +1495,7 @@ struct migrate_pages_stats { > int nr_thp_succeeded; /* THP migrated successfully */ > int nr_thp_failed; /* THP failed to be migrated */ > int nr_thp_split; /* THP split before migrating */ > + int nr_split; /* Large folio (include THP) split before migrating */ > }; > > /* > @@ -1614,6 +1615,7 @@ static int migrate_pages_batch(struct list_head *from, > int nr_retry_pages = 0; > int pass = 0; > bool is_thp = false; > + bool is_large = false; > struct folio *folio, *folio2, *dst = NULL, *dst2; > int rc, rc_saved = 0, nr_pages; > LIST_HEAD(unmap_folios); > @@ -1629,7 +1631,8 @@ static int migrate_pages_batch(struct list_head *from, > nr_retry_pages = 0; > > list_for_each_entry_safe(folio, folio2, from, lru) { > - is_thp = folio_test_large(folio) && folio_test_pmd_mappable(folio); > + is_large = folio_test_large(folio); > + is_thp = is_large && folio_test_pmd_mappable(folio); > nr_pages = folio_nr_pages(folio); > > cond_resched(); > @@ -1649,6 +1652,7 @@ static int migrate_pages_batch(struct list_head *from, > stats->nr_thp_failed++; > if (!try_split_folio(folio, split_folios)) { > stats->nr_thp_split++; > + stats->nr_split++; > continue; > } > stats->nr_failed_pages += nr_pages; > @@ -1677,11 +1681,12 @@ static int migrate_pages_batch(struct list_head *from, > nr_failed++; > stats->nr_thp_failed += is_thp; > /* Large folio NUMA faulting doesn't split to retry. */ > - if (folio_test_large(folio) && !nosplit) { > + if (is_large && !nosplit) { > int ret = try_split_folio(folio, split_folios); > > if (!ret) { > stats->nr_thp_split += is_thp; > + stats->nr_split += is_large; We have tested is_large above, so, "++" is enough here. Not a big deal, only change it if you think it's necessary. > break; > } else if (reason == MR_LONGTERM_PIN && > ret == -EAGAIN) { > @@ -1827,6 +1832,7 @@ static int migrate_pages_sync(struct list_head *from, new_folio_t get_new_folio, > stats->nr_succeeded += astats.nr_succeeded; > stats->nr_thp_succeeded += astats.nr_thp_succeeded; > stats->nr_thp_split += astats.nr_thp_split; > + stats->nr_split += astats.nr_split; > if (rc < 0) { > stats->nr_failed_pages += astats.nr_failed_pages; > stats->nr_thp_failed += astats.nr_thp_failed; > @@ -1834,7 +1840,11 @@ static int migrate_pages_sync(struct list_head *from, new_folio_t get_new_folio, > return rc; > } > stats->nr_thp_failed += astats.nr_thp_split; > - nr_failed += astats.nr_thp_split; > + /* > + * Do not count rc, as pages will be retried below. > + * Count nr_split only, since it includes nr_thp_split. > + */ > + nr_failed += astats.nr_split; > /* > * Fall back to migrate all failed folios one by one synchronously. All > * failed folios except split THPs will be retried, so their failure -- Best Regards, Huang, Ying