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[195.135.220.15]) by mx.google.com with ESMTPS id l1si1151083ejs.32.2019.02.13.04.33.42 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 13 Feb 2019 04:33:42 -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 E819DAFB8; Wed, 13 Feb 2019 12:33:41 +0000 (UTC) Date: Wed, 13 Feb 2019 13:33:39 +0100 From: Michal Hocko To: Oscar Salvador Cc: Mike Kravetz , akpm@linux-foundation.org, david@redhat.com, anthony.yznaga@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm,memory_hotplug: Explicitly pass the head to isolate_huge_page Message-ID: <20190213123339.GG4525@dhcp22.suse.cz> References: <20190208090604.975-1-osalvador@suse.de> <20190212083329.GN15609@dhcp22.suse.cz> <20190212134546.gubfir6zzwrvmunr@d104.suse.de> <20190212144026.GY15609@dhcp22.suse.cz> <52f7a47c-4a8b-c06d-04c0-48d9bb43823b@oracle.com> <20190213081310.zfxwb3svoqsxnuyc@d104.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190213081310.zfxwb3svoqsxnuyc@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 Wed 13-02-19 09:13:14, Oscar Salvador wrote: > On Tue, Feb 12, 2019 at 04:13:05PM -0800, Mike Kravetz wrote: > > Well, commit 94310cbcaa3c ("mm/madvise: enable (soft|hard) offline of > > HugeTLB pages at PGD level") should have allowed migration of gigantic > > pages. I believe it was added for 16GB pages on powerpc. However, due > > to subsequent changes I suspsect this no longer works. > > I will take a look, I am definitely interested in that. > Thanks for pointing it out Mike. > > > > > > This check doesn't make much sense in principle. Why should we bail out > > > based on a section size? We are offlining a pfn range. All that we care > > > about is whether the hugetlb is migrateable. > > > > Yes. Do note that the do_migrate_range is only called from __offline_pages > > with a start_pfn that was returned by scan_movable_pages. scan_movable_pages > > has the hugepage_migration_supported check for PageHuge pages. So, it would > > seem to be redundant to do another check in do_migrate_range. > > Well, the thing is that if the gigantic page does not start at the very beginning > of the memblock, and we do find migrateable pages before it in scan_movable_pages(), > the range that we will pass to do_migrate_ranges() will contain the gigantic page. > So we need the check there to cover that case too, although I agree that the current > check is misleading. Why isn't our check in has_unmovable_pages sufficient? -- Michal Hocko SUSE Labs