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[195.135.220.15]) by mx.google.com with ESMTPS id 43si1230107edu.318.2019.02.28.01.21.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 Feb 2019 01:21:55 -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 2EA8BAC5A; Thu, 28 Feb 2019 09:21:55 +0000 (UTC) Date: Thu, 28 Feb 2019 10:21:54 +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: <20190228092154.GV10588@dhcp22.suse.cz> References: <20190221094212.16906-1-osalvador@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190221094212.16906-1-osalvador@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 21-02-19 10:42:12, Oscar Salvador wrote: [...] > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index d5f7afda67db..04f6695b648c 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1337,8 +1337,7 @@ static unsigned long scan_movable_pages(unsigned long start, unsigned long end) > if (!PageHuge(page)) > continue; > head = compound_head(page); > - if (hugepage_migration_supported(page_hstate(head)) && > - page_huge_active(head)) > + if (page_huge_active(head)) > return pfn; > skip = (1 << compound_order(head)) - (page - head); > pfn += skip - 1; Is this part correct? Say we have a gigantic page which is migrateable. Now scan_movable_pages would skip it and we will not migrate it, no? > @@ -1378,10 +1377,6 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > > if (PageHuge(page)) { > struct page *head = compound_head(page); > - if (compound_order(head) > PFN_SECTION_SHIFT) { > - ret = -EBUSY; > - break; > - } > pfn = page_to_pfn(head) + (1< isolate_huge_page(head, &source); > continue; I think it would be much easier to have only this check removed in this patch. Because it is obviously bogus and wrong as well. The other check might be considered in a separate patch. -- Michal Hocko SUSE Labs