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[209.132.180.67]) by mx.google.com with ESMTP id a23si4988639plm.385.2019.05.09.17.41.33; Thu, 09 May 2019 17:42:08 -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; dkim=pass header.i=@google.com header.s=20161025 header.b=BnWMeilq; 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=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726776AbfEJAkK (ORCPT + 99 others); Thu, 9 May 2019 20:40:10 -0400 Received: from mail-yw1-f65.google.com ([209.85.161.65]:43201 "EHLO mail-yw1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726714AbfEJAkK (ORCPT ); Thu, 9 May 2019 20:40:10 -0400 Received: by mail-yw1-f65.google.com with SMTP id p19so3361057ywe.10 for ; Thu, 09 May 2019 17:40:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=kJIkcAZ6u5IJ9XmF7NOxVNNYB8HdaXRsalPuY1w3/z8=; b=BnWMeilq5CmV7xEOS7UTY0R8GZBvNiJUb5X8thIrkLC146CGJ28ux8O51ka94luUji ko51fW4KRyCWVOi/von/XCjTv5Bq+D0G0m8PuWDLMU8pmLoHkVAidAi/9MCw72ZNpUBN q7xTRHcayJCQmsiAPDShWGpwdLShGMWkoOMABic60GtN3IaFoPIX9eSVsFIkBfxpV7pe K1YZw/DNtI7wDyhVsKXKTR6evCj+wKBM/ZCKAVbXjVWRlyOHkScfk3FLQ4FnRkjbDi/x TcZbJlD57h5bUMnjLqNuuD1i4+gmaFje2JyxaP3cHRb97P+2aaN1Ctg2LNMnSUH9vTQS 7NZA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=kJIkcAZ6u5IJ9XmF7NOxVNNYB8HdaXRsalPuY1w3/z8=; b=XjOykYOugB4g4P25IVFy3WH4Z5a50QsfMmVjASHrW7ZhwAI9PI0dw2phM7cBW+ZRbQ ICGy7YdZqAseKKCC1ma6/0cS8iz6TccnJOp1nW/EfhzakF2mHudlHQa9BYB9UjdDgxq0 xRmgHlUr2mgoCzYlKkMgov/xGJAl/yZxyZLTDJfyVEq6IKxwIi7GWyGXCc8bUEnybq2Q YfoTWsVHaLhLiZtPriQ4RgLDXuEIrimlOkdwVSSTZMM3z9Sfcxpj33dY//PhIh7A8D/L RDgiz0/tmRHAHmXsO7rQfPE8fgw9F7aDQm9ASNzWz4cQGbglrAzzzSwWxJj23RmyDofr rtSQ== X-Gm-Message-State: APjAAAW/EQ68gXSJkrTUR8I6T2uyGuTMhp6Aq6Bc13GKPn1XmMxcjoxN qKaIyzPW596OKSOVh4XsCmmB3ESi0JO4S7BSI9plPA== X-Received: by 2002:a25:4147:: with SMTP id o68mr4131573yba.148.1557448809031; Thu, 09 May 2019 17:40:09 -0700 (PDT) MIME-Version: 1.0 References: <1557447392-61607-1-git-send-email-yang.shi@linux.alibaba.com> In-Reply-To: <1557447392-61607-1-git-send-email-yang.shi@linux.alibaba.com> From: Shakeel Butt Date: Thu, 9 May 2019 17:39:57 -0700 Message-ID: Subject: Re: [PATCH] mm: vmscan: correct nr_reclaimed for THP To: Yang Shi Cc: Huang Ying , Johannes Weiner , Michal Hocko , Mel Gorman , "Kirill A. Shutemov" , Hugh Dickins , Andrew Morton , Linux MM , LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yang Shi Date: Thu, May 9, 2019 at 5:16 PM To: , , , , , , Cc: , , > 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 Nice find. Reviewed-by: Shakeel Butt > --- > 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 > -- > 1.8.3.1 >