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[209.132.180.67]) by mx.google.com with ESMTP id s4si5502123plp.59.2019.05.09.19.15.11; Thu, 09 May 2019 19:16:07 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726862AbfEJCMn (ORCPT + 99 others); Thu, 9 May 2019 22:12:43 -0400 Received: from mga18.intel.com ([134.134.136.126]:11575 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726799AbfEJCMn (ORCPT ); Thu, 9 May 2019 22:12:43 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 09 May 2019 19:12:42 -0700 X-ExtLoop1: 1 Received: from yhuang-dev.sh.intel.com (HELO yhuang-dev) ([10.239.159.29]) by fmsmga007.fm.intel.com with ESMTP; 09 May 2019 19:12:40 -0700 From: "Huang\, Ying" To: Yang Shi Cc: , , , , , , , Subject: Re: [PATCH] mm: vmscan: correct nr_reclaimed for THP References: <1557447392-61607-1-git-send-email-yang.shi@linux.alibaba.com> Date: Fri, 10 May 2019 10:12:40 +0800 In-Reply-To: <1557447392-61607-1-git-send-email-yang.shi@linux.alibaba.com> (Yang Shi's message of "Fri, 10 May 2019 08:16:32 +0800") Message-ID: <87y33fjbvr.fsf@yhuang-dev.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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); Best Regards, Huang, Ying