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=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 12CB7C18E5B for ; Mon, 16 Mar 2020 22:38:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DEFCD20663 for ; Mon, 16 Mar 2020 22:38:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="VIU/bY9A" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732850AbgCPWiS (ORCPT ); Mon, 16 Mar 2020 18:38:18 -0400 Received: from mail-wm1-f68.google.com ([209.85.128.68]:55158 "EHLO mail-wm1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732739AbgCPWiS (ORCPT ); Mon, 16 Mar 2020 18:38:18 -0400 Received: by mail-wm1-f68.google.com with SMTP id n8so19452628wmc.4 for ; Mon, 16 Mar 2020 15:38:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:reply-to:references:mime-version :content-disposition:in-reply-to:user-agent; bh=1fBBOx02VcEYppdCNi5Xl2Em7WTei4uipjmvF9jzRYs=; b=VIU/bY9At5xVG9wGhnfLBhqN5QhHGKCCXmnN0KqYvjF5a52JUlieZIV/k3W7Zj8g1F MFNBVubiu0gUfDZ9X2oPNmd5daPqxz2V2TAmpJkUMKOmsWxB11u4e9+XB4aMZZpiWATd aLmESwpnTHPZNYPpBtRmFdVWiS/8d3rxkCcyUENSLnbb/NZq2Su3zNs3hOJJ4Iwsv6kY 6OAmsB+ki3dgNsnGBnnPErL28p9mGumyb/c6ufE/eE0zt4wX7PLbjPI09wsx+mjohR2y XeRLugX//utJqPKRSD2TAVvv1avqSVifEO0XR1NrCG75QuxCio5D4R8Qb/FXNN/Sp+lD Ml2A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:reply-to :references:mime-version:content-disposition:in-reply-to:user-agent; bh=1fBBOx02VcEYppdCNi5Xl2Em7WTei4uipjmvF9jzRYs=; b=o56cAxHzXi+eIwUuB7gBXD0vJPN4K9b0nUZfO6GMZrO53ftQckWFuRcle3uWOsq9sQ nfqDRo+jRPIAzNK5F9kLVVubIqrIcr4E5g1qoA+iDwQBXhh+1+rir3U5t3lk8gnGWo7N /BpuHGtwnNIzhOVJwFgWZU95YQSZLjumCin2SxtVkiW/GF7kbyvA6ulhIFlYp0Uu4hI/ PAnfrU/Dbj65aBqhCyIRVecZ2stYJmYK4Jpq+3CGZeGFhfRl5Dm2IX/phez24jLn/ILR H6762d9dXHKnVMdWEyzFVaQbTv5vzsIrB5EeBg5TUWsAhoAjeQeKPEmTnycfQJoG8DIj 2YDA== X-Gm-Message-State: ANhLgQ35ODq7xy/b/80D2UJ4AAhNgZ5g2fA5JhciLjChTwsGF9LIfQHo c3hytMM58ok8pWI7nRB39k8= X-Google-Smtp-Source: ADFU+vtChtP3lSKZ8/B9vEVi/mPCHm0+iHAc+RkasjUxXmYPvAx9TcuNhExKUL1CJUWuiaYhpG/LpA== X-Received: by 2002:a1c:3dd7:: with SMTP id k206mr1292164wma.147.1584398296193; Mon, 16 Mar 2020 15:38:16 -0700 (PDT) Received: from localhost ([185.92.221.13]) by smtp.gmail.com with ESMTPSA id w204sm1427927wma.1.2020.03.16.15.38.15 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 16 Mar 2020 15:38:15 -0700 (PDT) Date: Mon, 16 Mar 2020 22:38:14 +0000 From: Wei Yang To: "Huang, Ying" Cc: Wei Yang , Mika Penttil?? , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Dave Hansen , David Hildenbrand , Mel Gorman , Vlastimil Babka , Zi Yan , Michal Hocko , Peter Zijlstra , Minchan Kim , Johannes Weiner , Hugh Dickins Subject: Re: [RFC 2/3] mm: Add a new page flag PageLayzyFree() for MADV_FREE Message-ID: <20200316223814.dpzlmfpb6a2cus25@master> Reply-To: Wei Yang References: <20200228033819.3857058-1-ying.huang@intel.com> <20200228033819.3857058-3-ying.huang@intel.com> <20200315081854.rcqlmfckeqrh7fbt@master> <92d4b0fe-f592-8da6-0282-2ea8a015b247@nextfour.com> <20200315122217.45mioaxzuulwvx2f@master> <87pnddrt5t.fsf@yhuang-dev.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87pnddrt5t.fsf@yhuang-dev.intel.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 16, 2020 at 09:21:34AM +0800, Huang, Ying wrote: >Wei Yang writes: > >> On Sun, Mar 15, 2020 at 10:54:03AM +0200, Mika Penttil?? wrote: >>> >>> >>>On 15.3.2020 10.18, Wei Yang wrote: >>>> On Fri, Feb 28, 2020 at 11:38:18AM +0800, Huang, Ying wrote: >>>> > From: Huang Ying >>>> > >>>> > Now !PageSwapBacked() is used as the flag for the pages freed lazily >>>> > via MADV_FREE. This isn't obvious enough. So Dave suggested to add a >>>> > new page flag for that to improve the code readability. >>>> I am confused with the usage of PageSwapBacked(). >>>> >>>> Previously I thought this flag means the page is swapin, set in >>>> swapin_readahead(). While I found page_add_new_anon_rmap() would set it too. >>>> This means every anon page would carry this flag. Then what is this flag >>>> means? >>>> >>>> >>> >>>But not all PageSwapBacked() pages are anon, like shmem. >>> >> >> Yes, while it looks shmem is the only exception. > >Another exception is the pages freed lazily via MADV_FREE. > >> I am still struggling to understand the meaning of this flag. > >You can use `git blame` to find out the commit which introduces this >flag. Which describes why this flag is introduced. Thanks, I see the purpose is to distinguish a page: a) file backed b) or otheres This sound more clear. And now this flag is also used for MADV_FREE, which sounds a little abuse. This is the purpose of this patch to make a dedicate flag for MADV_FREE. BTW, the name, swapbacked, is a little misleading. Maybe just to me. But I can't come up with better naming. :-) > >Best Regards, >Huang, Ying > >>> >>>--Mika -- Wei Yang Help you, Help me