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 108E4C47082 for ; Tue, 8 Jun 2021 19:38:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E46A361182 for ; Tue, 8 Jun 2021 19:38:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236333AbhFHTkF (ORCPT ); Tue, 8 Jun 2021 15:40:05 -0400 Received: from mail-ej1-f54.google.com ([209.85.218.54]:40919 "EHLO mail-ej1-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237013AbhFHTjL (ORCPT ); Tue, 8 Jun 2021 15:39:11 -0400 Received: by mail-ej1-f54.google.com with SMTP id my49so17802466ejc.7 for ; Tue, 08 Jun 2021 12:37:18 -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=QjRnmhJy6MmKIjzJY5SHTAc0uY/wFjAOLooprD20PZOLNa+Jk71vmtpB0nVYk6pF02 27CV0G9CjEpsbN5gwbJ9QyBE80wfOII7CQWxWsaHNpfnZFSzwK+oImOQfK4O50ubRn5r /f2bh84A+eCnd4ILoiV2c57SNw38IGX7PrRFRJicMoa0J4IwXpj+t/F+CacR9WobyXHs Hb5wI7rwIPOXJJgVefXpw9bHyM9wnUW/Ci78tkoUULOQx00Wm6wFGTnbDaxA69bvdwO/ cUMajfxA/zW2+Gfodq9nGkHHRsyqBw6Zc6g7ocA7eUKydUFpZjGRvpcIlHODubMTpN0h UquA== X-Gm-Message-State: AOAM533lrIclazFSh+k2n5uuD1O6rogp/um/jUAI8g0w8s4Kk2tq4pTM QaXV4+4hAYn8rGM+bv0c0gU2H9zQrlJEQqJcF9g= 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" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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