From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3CDDBC433E4 for ; Mon, 27 Jul 2020 12:24:06 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id CA7022075A for ; Mon, 27 Jul 2020 12:24:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="WDzocfkZ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CA7022075A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 2143A6B0002; Mon, 27 Jul 2020 08:24:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1C4706B0003; Mon, 27 Jul 2020 08:24:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 08D186B0005; Mon, 27 Jul 2020 08:24:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0078.hostedemail.com [216.40.44.78]) by kanga.kvack.org (Postfix) with ESMTP id E43116B0002 for ; Mon, 27 Jul 2020 08:24:04 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 694613625 for ; Mon, 27 Jul 2020 12:24:04 +0000 (UTC) X-FDA: 77083772808.13.hook17_36014a426f61 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin13.hostedemail.com (Postfix) with ESMTP id 3F34318140B69 for ; Mon, 27 Jul 2020 12:24:04 +0000 (UTC) X-HE-Tag: hook17_36014a426f61 X-Filterd-Recvd-Size: 9071 Received: from us-smtp-delivery-1.mimecast.com (us-smtp-2.mimecast.com [207.211.31.81]) by imf31.hostedemail.com (Postfix) with ESMTP for ; Mon, 27 Jul 2020 12:24:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1595852642; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=ld82Mx2jdY88y70RF5lgMLftQqJLR4BjtuJgddo1PVw=; b=WDzocfkZGmxhZXbiL/PhA9i5k3mlJSa1saxBzvL8YFoioCXE1yoPGbrOXQIuZEyDuFN4CS EkNkFVXIvUUMiStKsukV+KkqIMbF+55YcZjO+NNGKeOftmNBKWELsKrWhiS4887Ag+n+q0 ANSNCNq7+npt45ebKfaE/mZpXflWdIc= 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-153-hY0ts04GOnyiXrCDnJU5Pg-1; Mon, 27 Jul 2020 08:24:00 -0400 X-MC-Unique: hY0ts04GOnyiXrCDnJU5Pg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 91F7684CD40; Mon, 27 Jul 2020 12:23:59 +0000 (UTC) Received: from [10.36.114.48] (ovpn-114-48.ams2.redhat.com [10.36.114.48]) by smtp.corp.redhat.com (Postfix) with ESMTP id F051379D02; Mon, 27 Jul 2020 12:23:52 +0000 (UTC) Subject: Re: [PATCH v1 5/6] mm/page_alloc: restrict ZONE_MOVABLE optimization in has_unmovable_pages() to memory offlining To: linux-kernel@vger.kernel.org Cc: virtualization@lists.linux-foundation.org, linux-mm@kvack.org, Andrew Morton , Michal Hocko , "Michael S . Tsirkin" References: <20200630142639.22770-1-david@redhat.com> <20200630142639.22770-6-david@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63W5Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAjwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat GmbH Message-ID: <8f0dfc91-bf91-4d9c-a4f5-ebaeb568b39b@redhat.com> Date: Mon, 27 Jul 2020 14:23:50 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200630142639.22770-6-david@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Rspamd-Queue-Id: 3F34318140B69 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 Content-Transfer-Encoding: quoted-printable 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 30.06.20 16:26, David Hildenbrand wrote: > We can already have pages that can be offlined but not allocated in > ZONE_MOVABLE - PageHWPoison pages. While these pages can be skipped whe= n > offlining ("moving them to /dev/null"), we cannot move them when > allocating. >=20 > virtio-mem managed memory is similar. The logical memory holes > corresponding to unplug memory ranges can be skipped when offlining, > however, the pages cannot be moved. Currently, virtio-mem special-cases > ZONE_MOVABLE, such that: > - partially plugged memory blocks it added to Linux cannot be onlined t= o > ZONE_MOVABLE > - when unplugging memory, it will never consider memory blocks that wer= e > onlined to ZONE_MOVABLE >=20 > We also want to support ZONE_MOVABLE in virtio-mem for both cases. Note > that virtio-mem does not blindly try to unplug random pages within its > managed memory region. It always plugs memory left-to-right and tries t= o > unplug memory right-to-left - in roughly MAX_ORDER - 1 granularity. In > theory, the movable ZONE part would only shrink when unplugging memory > from ZONE_MOVABLE. >=20 > Let's perform the ZONE_MOVABLE optimization only for memory offlining, > such that we reduce the number of false positives from > has_unmovable_pages() in case of alloc_contig_range() on ZONE_MOVABLE. >=20 > Note: We currently don't seem to have any user of alloc_contig_range() > that actually uses ZONE_MOVABLE. This change is mostly valuable for the > documentation. >=20 > Cc: Andrew Morton > Cc: Michal Hocko > Cc: Michael S. Tsirkin > Signed-off-by: David Hildenbrand > --- > mm/page_alloc.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) >=20 > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index bd3ebf08f09b9..45077d74d975d 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -8237,9 +8237,12 @@ struct page *has_unmovable_pages(struct zone *zo= ne, struct page *page, > /* > * If the zone is movable and we have ruled out all reserved > * pages then it should be reasonably safe to assume the rest > - * is movable. > + * is movable. As we can have some pages in the movable zone > + * that are only considered movable for memory offlining (esp., > + * PageHWPoison and PageOffline that will be skipped), we > + * perform this optimization only for memory offlining. > */ > - if (zone_idx(zone) =3D=3D ZONE_MOVABLE) > + if ((flags & MEMORY_OFFLINE) && zone_idx(zone) =3D=3D ZONE_MOVABLE) > continue; > =20 > /* >=20 So, as we don't have any alloc_contig_range() users that use ZONE_MOVABLE for now, and virtio-mem will be the only one for now (which accounts for 50% of the special cases - PG_offline), I think we might drop this patch. Worst think is that if we ever have other alloc_contig_range() users, that we return "false" from has_unmovable_pages() and fail later when trying to migrate/isolate all pages. This should, however, only happen in rare cases (and there are already other cases where we have basically unmovable data - long-term pinnings). On the plus side, keeping the ZONE_MOVABLE optimizations here also allows virtio-mem to better tolerate unstable page flags when trying to alloc_contig_range(). Thoughts? --=20 Thanks, David / dhildenb