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=-7.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 0E6FEC47082 for ; Tue, 8 Jun 2021 19:36:21 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A84E861001 for ; Tue, 8 Jun 2021 19:36:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A84E861001 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 017046B006C; Tue, 8 Jun 2021 15:36:20 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EE28A6B006E; Tue, 8 Jun 2021 15:36:19 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D35F96B0070; Tue, 8 Jun 2021 15:36:19 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0181.hostedemail.com [216.40.44.181]) by kanga.kvack.org (Postfix) with ESMTP id 9D3866B006C for ; Tue, 8 Jun 2021 15:36:19 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 4B8769427 for ; Tue, 8 Jun 2021 19:36:19 +0000 (UTC) X-FDA: 78231562878.27.39077A7 Received: from mail-ej1-f47.google.com (mail-ej1-f47.google.com [209.85.218.47]) by imf21.hostedemail.com (Postfix) with ESMTP id 53696E00026E for ; Tue, 8 Jun 2021 19:36:14 +0000 (UTC) Received: by mail-ej1-f47.google.com with SMTP id c10so34463061eja.11 for ; Tue, 08 Jun 2021 12:36:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=JKTPUiA9elPvGMQvcCJuNHjTNIa7sShKwEDWPPy8EEM=; b=YJhPa5F64W5qsXB46vVhKbDqi5siZegf325mLIcJZloLiygLe2QcoCk01IJMSn1A5Y l0XKyEEy81MvYt8ozVZv1tof/OjybSmlr6M3a3l/SYcT3xdsP6d0mlhlWeXukMsqLPlx 7RiIOhXwx8BUpt7XyA7Mm+eS2zARv05N5C7Vw9oUeMkTLZnl8QXHJfgA+TdGgIQAis8d sOfu3HQ7pWUAhjYgbWI2xeWtboHtq1zSPo5E2wHJDlz7b4krRVlhyGSH+huv2jNBELRz yqjJP07h54OxYiyUGieD5U3L2GV6gPzAS4KzHrDR82CU3cC3y+W3CY8rfphTBQOGT+PI Hn6w== 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=JKTPUiA9elPvGMQvcCJuNHjTNIa7sShKwEDWPPy8EEM=; b=H/q4cGj7W3sxiZTYNK2M0DtvV3cTgBkhNXB3MqeiQ45ReD5pz6rNejmLrNtCYaZXUO czoVSAYdeYgdGK7JhiKuuwsyJFLDTPbW8WkwVZ634lpYrUqZ6pCkMi4YCMiRZLsWEXbz 80GRZlMtM7qA9SodLrKkYaIlutJLeZmxcVXIKey8ycrwa8IKllE7VFOJssMSC4awGbIr VfPsRXK3LLzfJ4IDteaCbEC0NJe1kcWpnY4z7nk5EfLL0HNni3NzWSsyZhvl6kfjFQs8 cQP0o3yn7xY6g2AJGWiUEk8qplPSJobPTbhnQsZJO3Moe3IApo9xFp10fUQG3+T2GNsI e/Yg== X-Gm-Message-State: AOAM5336i7UWBeGkjtUxAFVF5PUrIQupWb2tokBwykeHvPq6QNgXcxNp S7L7qzAou5W4j5hzUwl7X8wVNP14LE34XwTInyE= X-Google-Smtp-Source: ABdhPJzy5smI5eapf2uWMTdSduOVdqYwN94fU3XJCWeuFH21fThypuQKQ4eBn2/DZmf65LeRsf+9XZ74nOyvkjySw2c= X-Received: by 2002:a17:907:7b97:: with SMTP id ne23mr24957151ejc.499.1623180977706; Tue, 08 Jun 2021 12:36:17 -0700 (PDT) MIME-Version: 1.0 References: <20210604203513.240709-1-shy828301@gmail.com> In-Reply-To: From: Yang Shi Date: Tue, 8 Jun 2021 12:36:05 -0700 Message-ID: Subject: Re: [PATCH] mm: mempolicy: don't have to split pmd for huge zero page To: Michal Hocko Cc: Zi Yan , nao.horiguchi@gmail.com, "Kirill A. Shutemov" , Hugh Dickins , Andrew Morton , Linux MM , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=gmail.com header.s=20161025 header.b=YJhPa5F6; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf21.hostedemail.com: domain of shy828301@gmail.com designates 209.85.218.47 as permitted sender) smtp.mailfrom=shy828301@gmail.com X-Rspamd-Server: rspam02 X-Stat-Signature: z11ianw5sbh8g65j78nic81byuu59wef X-Rspamd-Queue-Id: 53696E00026E X-HE-Tag: 1623180974-554754 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jun 8, 2021 at 10:49 AM Michal Hocko wrote: > > On Tue 08-06-21 10:15:36, Yang Shi wrote: > [...] > > I did some archeology, the findings are: > > > > The zero page has PageReserved flag set, it was skipped by the > > explicit PageReserved check in mempolicy.c since commit f4598c8b3678 > > ("[PATCH] migration: make sure there is no attempt to migrate reserved > > pages."). The zero page was not used anymore by do_anonymous_page() > > since 2.6.24 by commit 557ed1fa2620 ("remove ZERO_PAGE"), then > > reinstated by commit a13ea5b759645 ("mm: reinstate ZERO_PAGE") and > > this commit added zero page check in vm_normal_page(), so mempolicy > > doesn't depend on PageReserved check to skip zero page anymore since > > then. > > > > So the zero page is skipped by mempolicy.c since 2.6.16. > > Thanks a lot! This is really useful. Can you just add it to the > changelog so others do not have to go through the painful archeology. > > With that, feel free to add > Acked-by: Michal Hocko Thanks. Will add that into v2. > > Thanls! > -- > Michal Hocko > SUSE Labs