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[195.135.220.15]) by mx.google.com with ESMTPS id f7si7089014edm.167.2019.02.28.06.08.17 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 Feb 2019 06:08:17 -0800 (PST) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 7B614ADAA; Thu, 28 Feb 2019 14:08:17 +0000 (UTC) Date: Thu, 28 Feb 2019 15:08:17 +0100 From: Michal Hocko To: Oscar Salvador Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, david@redhat.com, mike.kravetz@oracle.com Subject: Re: [RFC PATCH] mm,memory_hotplug: Unlock 1GB-hugetlb on x86_64 Message-ID: <20190228140817.GD10588@dhcp22.suse.cz> References: <20190221094212.16906-1-osalvador@suse.de> <20190228092154.GV10588@dhcp22.suse.cz> <20190228094104.wbeaowsx25ckpcc7@d104.suse.de> <20190228095535.GX10588@dhcp22.suse.cz> <20190228101949.qnnzgdhyn6deevnm@d104.suse.de> <20190228121115.GA10588@dhcp22.suse.cz> <20190228133951.outlsq7swhp3nffr@d104.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190228133951.outlsq7swhp3nffr@d104.suse.de> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Thu 28-02-19 14:40:54, Oscar Salvador wrote: > On Thu, Feb 28, 2019 at 01:11:15PM +0100, Michal Hocko wrote: > > On Thu 28-02-19 11:19:52, Oscar Salvador wrote: > > > On Thu, Feb 28, 2019 at 10:55:35AM +0100, Michal Hocko wrote: > > > > You seemed to miss my point or I am wrong here. If scan_movable_pages > > > > skips over a hugetlb page then there is nothing to migrate it and it > > > > will stay in the pfn range and the range will not become idle. > > > > > > I might be misunterstanding you, but I am not sure I get you. > > > > > > scan_movable_pages() can either skip or not a hugetlb page. > > > In case it does, pfn will be incremented to skip the whole hugetlb > > > range. > > > If that happens, pfn will hold the next non-hugetlb page. > > > > And as a result the previous hugetlb page doesn't get migrated right? > > What does that mean? Well, the page is still in use and we cannot > > proceed with offlining because the full range is not isolated right? > > I might be clumsy today but I still fail to see the point of concern here. No, it's me who is daft. I have misread the patch and seen that also page_huge_active got removed. Now it makes perfect sense to me because active pages are still handled properly. I will leave the decision whether to split up the patch to you. Acked-by: Michal Hocko and sorry for being dense here. -- Michal Hocko SUSE Labs