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 X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,UNPARSEABLE_RELAY autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 930C7C04AB1 for ; Fri, 10 May 2019 02:25:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 609EB217F5 for ; Fri, 10 May 2019 02:25:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726899AbfEJCZ2 (ORCPT ); Thu, 9 May 2019 22:25:28 -0400 Received: from out30-56.freemail.mail.aliyun.com ([115.124.30.56]:55585 "EHLO out30-56.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726810AbfEJCZ1 (ORCPT ); Thu, 9 May 2019 22:25:27 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R151e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0TRIa4cz_1557455120; Received: from US-143344MP.local(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0TRIa4cz_1557455120) by smtp.aliyun-inc.com(127.0.0.1); Fri, 10 May 2019 10:25:23 +0800 Subject: Re: [PATCH] mm: vmscan: correct nr_reclaimed for THP To: "Huang, Ying" Cc: hannes@cmpxchg.org, mhocko@suse.com, mgorman@techsingularity.net, kirill.shutemov@linux.intel.com, hughd@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1557447392-61607-1-git-send-email-yang.shi@linux.alibaba.com> <87y33fjbvr.fsf@yhuang-dev.intel.com> From: Yang Shi Message-ID: <1fb73973-f409-1411-423b-c48895d3dde8@linux.alibaba.com> Date: Thu, 9 May 2019 19:25:20 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <87y33fjbvr.fsf@yhuang-dev.intel.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/9/19 7:12 PM, Huang, Ying wrote: > Yang Shi writes: > >> Since commit bd4c82c22c36 ("mm, THP, swap: delay splitting THP after >> swapped out"), THP can be swapped out in a whole. But, nr_reclaimed >> still gets inc'ed by one even though a whole THP (512 pages) gets >> swapped out. >> >> This doesn't make too much sense to memory reclaim. For example, direct >> reclaim may just need reclaim SWAP_CLUSTER_MAX pages, reclaiming one THP >> could fulfill it. But, if nr_reclaimed is not increased correctly, >> direct reclaim may just waste time to reclaim more pages, >> SWAP_CLUSTER_MAX * 512 pages in worst case. >> >> This change may result in more reclaimed pages than scanned pages showed >> by /proc/vmstat since scanning one head page would reclaim 512 base pages. >> >> Cc: "Huang, Ying" >> Cc: Johannes Weiner >> Cc: Michal Hocko >> Cc: Mel Gorman >> Cc: "Kirill A . Shutemov" >> Cc: Hugh Dickins >> Signed-off-by: Yang Shi >> --- >> I'm not quite sure if it was the intended behavior or just omission. I tried >> to dig into the review history, but didn't find any clue. I may miss some >> discussion. >> >> mm/vmscan.c | 6 +++++- >> 1 file changed, 5 insertions(+), 1 deletion(-) >> >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index fd9de50..7e026ec 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -1446,7 +1446,11 @@ static unsigned long shrink_page_list(struct list_head *page_list, >> >> unlock_page(page); >> free_it: >> - nr_reclaimed++; >> + /* >> + * THP may get swapped out in a whole, need account >> + * all base pages. >> + */ >> + nr_reclaimed += (1 << compound_order(page)); >> >> /* >> * Is there need to periodically free_page_list? It would > Good catch! Thanks! > > How about to change this to > > > nr_reclaimed += hpage_nr_pages(page); Either is fine to me. Is this faster than "1 << compound_order(page)"? > > Best Regards, > Huang, Ying