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Wed, 25 Nov 2020 06:42:00 -0500 X-MC-Unique: UaTaFx1OOpiQPcHNG11D1g-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9AB0A1E7CE; Wed, 25 Nov 2020 11:41:58 +0000 (UTC) Received: from [10.36.112.131] (ovpn-112-131.ams2.redhat.com [10.36.112.131]) by smtp.corp.redhat.com (Postfix) with ESMTP id B9F415D9C2; Wed, 25 Nov 2020 11:41:56 +0000 (UTC) Subject: Re: [PATCH 1/1] mm: compaction: avoid fast_isolate_around() to set pageblock_skip on reserved pages From: David Hildenbrand To: Mel Gorman Cc: Andrea Arcangeli , Vlastimil Babka , Andrew Morton , linux-mm@kvack.org, Qian Cai , Michal Hocko , linux-kernel@vger.kernel.org, Mike Rapoport , Baoquan He References: <35F8AADA-6CAA-4BD6-A4CF-6F29B3F402A4@redhat.com> <20201125103933.GM3306@suse.de> <5f01bde6-fe31-9b0e-f288-06b82598a8b3@redhat.com> Organization: Red Hat GmbH Message-ID: <33612969-92a1-6c49-a2e0-3a95715b1e7f@redhat.com> Date: Wed, 25 Nov 2020 12:41:55 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <5f01bde6-fe31-9b0e-f288-06b82598a8b3@redhat.com> Content-Type: text/plain; charset=iso-8859-15 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 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 25.11.20 12:04, David Hildenbrand wrote: > On 25.11.20 11:39, Mel Gorman wrote: >> On Wed, Nov 25, 2020 at 07:45:30AM +0100, David Hildenbrand wrote: >>>> Something must have changed more recently than v5.1 that caused the >>>> zoneid of reserved pages to be wrong, a possible candidate for the >>>> real would be this change below: >>>> >>>> + __init_single_page(pfn_to_page(pfn), pfn, 0, 0); >>>> >>> >>> Before that change, the memmap of memory holes were only zeroed out. So the zones/nid was 0, however, pages were not reserved and had a refcount of zero - resulting in other issues. >>> >>> Most pfn walkers shouldn???t mess with reserved pages and simply skip them. That would be the right fix here. >>> >> >> Ordinarily yes, pfn walkers should not care about reserved pages but it's >> still surprising that the node/zone linkages would be wrong for memory >> holes. If they are in the middle of a zone, it means that a hole with >> valid struct pages could be mistaken for overlapping nodes (if the hole >> was in node 1 for example) or overlapping zones which is just broken. > > I agree within zones - but AFAIU, the issue is reserved memory between > zones, right? Double checking, I was confused. This applies also to memory holes within zones in x86. -- Thanks, David / dhildenb