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bh=pe+hNlBlJokGLROd+OkEWWry9BPX/DPDTBCU01H/1hU=; b=QSik9qiqRGJNw9K/LkoLf/VVtOTau7Iih7oy/EqP05P1kEwg/b57hWRo/ya/oABjWOLs0B KcfvxDX0KBOlBuIkPbj+laoJCAnavK9O7zEG1rfbAdM7p4SDHUOBYntilPQqQRGn3885AT XaxyG57CY1jXVcfC2xXv4l8x2762Fws= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-330-o-0RnCYpO9iZCunD2zEs-Q-1; Tue, 04 Aug 2020 06:04:24 -0400 X-MC-Unique: o-0RnCYpO9iZCunD2zEs-Q-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 A4059100CCC8; Tue, 4 Aug 2020 10:04:22 +0000 (UTC) Received: from [10.36.113.95] (ovpn-113-95.ams2.redhat.com [10.36.113.95]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7FC1C5D9F7; Tue, 4 Aug 2020 10:04:15 +0000 (UTC) Subject: Re: [PATCH v3 6/6] mm: document semantics of ZONE_MOVABLE To: Mike Rapoport References: <20200804072408.5481-1-david@redhat.com> <20200804072408.5481-7-david@redhat.com> <20200804093323.GB8243@kernel.org> <65deeb21-63fe-d1c1-bb87-74a08035f79a@redhat.com> <20200804100333.GC8243@kernel.org> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200804100333.GC8243@kernel.org> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Cc: Pankaj Gupta , Michal Hocko , Baoquan He , "Michael S . Tsirkin" , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-mm@kvack.org, Andrew Morton , Mike Kravetz X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On 04.08.20 12:03, Mike Rapoport wrote: > On Tue, Aug 04, 2020 at 11:55:10AM +0200, David Hildenbrand wrote: >> On 04.08.20 11:33, Mike Rapoport wrote: >>> On Tue, Aug 04, 2020 at 09:24:08AM +0200, David Hildenbrand wrote: >>>> Let's document what ZONE_MOVABLE means, how it's used, and which special >>>> cases we have regarding unmovable pages (memory offlining vs. migration / >>>> allocations). >>>> >>>> Cc: Andrew Morton >>>> Cc: Michal Hocko >>>> Cc: Michael S. Tsirkin >>>> Cc: Mike Kravetz >>>> Cc: Mike Rapoport >>>> Cc: Pankaj Gupta >>>> Cc: Baoquan He >>>> Signed-off-by: David Hildenbrand >>> >>> Several nits below, othersize >>> >>> Acked-by: Mike Rapoport >>> >>>> --- >>>> include/linux/mmzone.h | 34 ++++++++++++++++++++++++++++++++++ >>>> 1 file changed, 34 insertions(+) >>>> >>>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h >>>> index f6f884970511d..600d449e7d9e9 100644 >>>> --- a/include/linux/mmzone.h >>>> +++ b/include/linux/mmzone.h >>>> @@ -372,6 +372,40 @@ enum zone_type { >>>> */ >>>> ZONE_HIGHMEM, >>>> #endif >>>> + /* >>>> + * ZONE_MOVABLE is similar to ZONE_NORMAL, except that it *primarily* >>>> + * only contains movable pages. Main use cases are to make memory >>> >>> "Primarily only" sounds awkward. Maybe >>> >>> ... except that it only contains movable pages with few exceptional >>> cases described below. >>> >>> And then >>> >>> Main use cases for ZONE_MOVABLE are ... >> >> Ack! >> >>> >>>> + * offlining more likely to succeed, and to locally limit unmovable >>>> + * allocations - e.g., to increase the number of THP/huge pages. >>>> + * Notable special cases are: >>>> + * >>>> + * 1. Pinned pages: (Long-term) pinning of movable pages might >>> >>> ^long, capital L looked out of place for me >> >> Ack! >> >>> >>>> + * essentially turn such pages unmovable. Memory offlining might >>>> + * retry a long time. >>>> + * 2. memblock allocations: kernelcore/movablecore setups might create >>>> + * situations where ZONE_MOVABLE contains unmovable allocations >>>> + * after boot. Memory offlining and allocations fail early. >>>> + * 3. Memory holes: Such pages cannot be allocated. Applies only to >>>> + * boot memory, not hotplugged memory. Memory offlining and >>>> + * allocations fail early. >>> >>> I would clarify where page struct for abscent memory come from >> >> Something like: >> >> Memory holes: We might have a memmap for memory holes, for example, if > > ^w ;-) > >> we have sections that are only partially System RAM. Such pages cannot >> be ... > > How about > > ... sections that are only partially populated > > ? Yeah, shorter. Thanks! -- Thanks, David / dhildenb _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization