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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 EA027C2D0EC for ; Sat, 28 Mar 2020 00:20:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BCED1206F2 for ; Sat, 28 Mar 2020 00:20:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=shutemov-name.20150623.gappssmtp.com header.i=@shutemov-name.20150623.gappssmtp.com header.b="krBxnjhL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726661AbgC1AT7 (ORCPT ); Fri, 27 Mar 2020 20:19:59 -0400 Received: from mail-lj1-f194.google.com ([209.85.208.194]:44949 "EHLO mail-lj1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726212AbgC1AT7 (ORCPT ); Fri, 27 Mar 2020 20:19:59 -0400 Received: by mail-lj1-f194.google.com with SMTP id p14so12021051lji.11 for ; Fri, 27 Mar 2020 17:19:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=/27FgRjA8d032GtY7HE3lQ/cMxK1Gx032Jbtg6BA4Lw=; b=krBxnjhLC4IxLHtvfiBB/MAx5jXsWZWo19W02YfJ99zFKEcpCWKMMvPlHGDu8tbQ0M RwYviRx72BPRZJofn53BR5kjbou5+VtC/RmobQhCAgmyWtbNaGU35yYrsi0pF/c3kVPQ WSTHmyIlmJ4YxIqy7WiosJXu0qyDGv+nD9oNGJ4hTDjvz1Dt4cP1cIPsXHxfPBcEF6IX lED74wmdxBYdqmpm+cEXA0wgdZfnfTWD5lsQV1chWo/t2CXn1iqWEXxzU75rovCsQVZE 0gbD/iFoNRs9GXuvkAu7i9ek2/EtH9rDXBmqjm7/YJJM3LrtMHGy7kxCKNwQW3j+KQo8 QURA== 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:references :mime-version:content-disposition:in-reply-to; bh=/27FgRjA8d032GtY7HE3lQ/cMxK1Gx032Jbtg6BA4Lw=; b=Jz3Cnqza2CK85vp8eduwSBceIe39BgL5Z1QBq/tSabicQ4ejgcYcdeeZ6HFS3HqquU /tOD0y2U6ghIfBsYGCCXdO1q3U8bnb8/I1mEqbeVtSXMdKpMKm7Jk2+aSW8fVqW8QNfj 6C3ObL6upipvrqYJqPRMazLL64VeMmUkhTXUvOsKsIrRrMZpG0FqV8eeOdJ0fld4JiDo 7YbJ0ckveXDf/JactdkHIRR3B6M9Nl1jxSovIG2k8xuoUd8fRXEmeaEW/Y4GKVfhyXv3 uRKfubjWq+IVqTfMKaKqZQEDztl8RhHviqIJ1hVMYoSfcLf9jSIiPMUHPmeajENRV0Gq iNjw== X-Gm-Message-State: AGi0PuaiYIAnZYxs2D6eUvaNiN8h+8qKgZgBTKzno8X611E1iDoxdyW4 bYwC5kPTAfzIU6iemAbWSiTSCNCRHqY= X-Google-Smtp-Source: APiQypKQgaTKxolHVLHUW/w20cfNSovlvtiHv+kLPb6uIoyPq8z2v8ya7yFzs5391TlI3xY22kgeXw== X-Received: by 2002:a05:651c:1061:: with SMTP id y1mr765888ljm.285.1585354796426; Fri, 27 Mar 2020 17:19:56 -0700 (PDT) Received: from box.localdomain ([86.57.175.117]) by smtp.gmail.com with ESMTPSA id e14sm3247401ljb.97.2020.03.27.17.19.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Mar 2020 17:19:55 -0700 (PDT) Received: by box.localdomain (Postfix, from userid 1000) id F2CFB100D24; Sat, 28 Mar 2020 03:19:59 +0300 (+03) Date: Sat, 28 Mar 2020 03:19:59 +0300 From: "Kirill A. Shutemov" To: Zi Yan Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" Subject: Re: [PATCH] thp: Simplify splitting PMD mapping huge zero page Message-ID: <20200328001959.ggi74gch42soulus@box> References: <20200327170353.17734-1-kirill.shutemov@linux.intel.com> <1437F525-1510-45CD-A67F-13DF525083B4@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1437F525-1510-45CD-A67F-13DF525083B4@nvidia.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 27, 2020 at 01:23:07PM -0400, Zi Yan wrote: > On 27 Mar 2020, at 13:03, Kirill A. Shutemov wrote: > > > Splitting PMD mapping huge zero page can be simplified a lot: we can > > just unmap it and fallback to PTE handling. > > So we will have an extra page fault for the first read to each subpage, > but nothing changes if the first access to a subpage is a write, right? > BTW, what is the motivation for this code simplification? Match what we do for file-THP. I found a problem with the patch. Ignore it for now. -- Kirill A. Shutemov