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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 3B880C4743D for ; Tue, 8 Jun 2021 17:49:46 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C9033610E5 for ; Tue, 8 Jun 2021 17:49:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C9033610E5 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 411EB6B006C; Tue, 8 Jun 2021 13:49:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3C2206B006E; Tue, 8 Jun 2021 13:49:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 263406B0070; Tue, 8 Jun 2021 13:49:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0007.hostedemail.com [216.40.44.7]) by kanga.kvack.org (Postfix) with ESMTP id EC1366B006C for ; Tue, 8 Jun 2021 13:49:44 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 8E0A2584F for ; Tue, 8 Jun 2021 17:49:44 +0000 (UTC) X-FDA: 78231294288.22.2B057BE Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by imf29.hostedemail.com (Postfix) with ESMTP id F2B4A37C for ; Tue, 8 Jun 2021 17:49:38 +0000 (UTC) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id EAEE6219BB; Tue, 8 Jun 2021 17:49:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1623174582; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=xQ0exyzvqmDVh1jljb/vutVtcq9WcTozqWGSBLWacEI=; b=kFFb+FbwC60F6qZnPlFdh9NRZGvnBm8ACc2LvCxznN4VzDquiF6R4x/WGbnBSxRMEY/xBB mWiw3Uh0daGhTdenBStjZlVLkxh7SeOWXq96qJstjjNDfPGNaJl98fePGbDuIJYU+SBy5Z EASgZMnknC0g6TiyOXLa3M0e4OONWto= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 94C83A3B97; Tue, 8 Jun 2021 17:49:42 +0000 (UTC) Date: Tue, 8 Jun 2021 19:49:42 +0200 From: Michal Hocko To: Yang Shi Cc: Zi Yan , nao.horiguchi@gmail.com, "Kirill A. Shutemov" , Hugh Dickins , Andrew Morton , Linux MM , Linux Kernel Mailing List Subject: Re: [PATCH] mm: mempolicy: don't have to split pmd for huge zero page Message-ID: References: <20210604203513.240709-1-shy828301@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: F2B4A37C Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=kFFb+Fbw; spf=pass (imf29.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.28 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com X-Stat-Signature: s4d3eja54trukrmqy86ajsjcfap7pz8o X-HE-Tag: 1623174578-235349 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 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 Thanls! -- Michal Hocko SUSE Labs