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Fri, 25 Sep 2020 06:39:52 -0400 X-MC-Unique: U8kmAIcDON2MDJw36pfrZg-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 A2FE11091066; Fri, 25 Sep 2020 10:39:50 +0000 (UTC) Received: from [10.36.112.211] (ovpn-112-211.ams2.redhat.com [10.36.112.211]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0EA5C73667; Fri, 25 Sep 2020 10:39:47 +0000 (UTC) Subject: Re: [PATCH 7/9] mm, page_alloc: move draining pcplists to page isolation users To: Vlastimil Babka , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Michal Hocko , Pavel Tatashin , Oscar Salvador , Joonsoo Kim References: <20200922143712.12048-1-vbabka@suse.cz> <20200922143712.12048-8-vbabka@suse.cz> 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: <678262d6-cb82-d78c-9738-db70ab01f6de@redhat.com> Date: Fri, 25 Sep 2020 12:39:47 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200922143712.12048-8-vbabka@suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 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 22.09.20 16:37, Vlastimil Babka wrote: > Currently, pcplists are drained during set_migratetype_isolate() which means > once per pageblock processed start_isolate_page_range(). This is somewhat > wasteful. Moreover, the callers might need different guarantees, and the > draining is currently prone to races and does not guarantee that no page > from isolated pageblock will end up on the pcplist after the drain. > > Better guarantees are added by later patches and require explicit actions > by page isolation users that need them. Thus it makes sense to move the > current imperfect draining to the callers also as a preparation step. > > Suggested-by: Pavel Tatashin I would have guessed I suggested that one first as well :) https://lkml.kernel.org/r/6ec66eb9-eeba-5076-af97-cef59ed5cbaa@redhat.com (But honestly, I don't care :), just stumbled over it) > Signed-off-by: Vlastimil Babka > --- > mm/memory_hotplug.c | 11 ++++++----- > mm/page_alloc.c | 2 ++ > mm/page_isolation.c | 10 +++++----- > 3 files changed, 13 insertions(+), 10 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 9db80ee29caa..08f729922e18 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1524,6 +1524,8 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages) > goto failed_removal; > } > > + drain_all_pages(zone); > + > arg.start_pfn = start_pfn; > arg.nr_pages = nr_pages; > node_states_check_changes_offline(nr_pages, zone, &arg); > @@ -1574,11 +1576,10 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages) > } > > /* > - * per-cpu pages are drained in start_isolate_page_range, but if > - * there are still pages that are not free, make sure that we > - * drain again, because when we isolated range we might > - * have raced with another thread that was adding pages to pcp > - * list. > + * per-cpu pages are drained after start_isolate_page_range, but > + * if there are still pages that are not free, make sure that we > + * drain again, because when we isolated range we might have > + * raced with another thread that was adding pages to pcp list. > * > * Forward progress should be still guaranteed because > * pages on the pcp list can only belong to MOVABLE_ZONE > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 901907799bdc..4e37bc3f6077 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -8432,6 +8432,8 @@ int alloc_contig_range(unsigned long start, unsigned long end, > if (ret) > return ret; > > + drain_all_pages(cc.zone); > + > /* > * In case of -EBUSY, we'd like to know which page causes problem. > * So, just fall through. test_pages_isolated() has a tracepoint > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index abfe26ad59fd..57d8bc1e7760 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -49,7 +49,6 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_ > > __mod_zone_freepage_state(zone, -nr_pages, mt); > spin_unlock_irqrestore(&zone->lock, flags); > - drain_all_pages(zone); > return 0; > } > > @@ -167,11 +166,12 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages) > * > * Please note that there is no strong synchronization with the page allocator > * either. Pages might be freed while their page blocks are marked ISOLATED. > - * In some cases pages might still end up on pcp lists and that would allow > + * A call to drain_all_pages() after isolation can flush most of them. However > + * in some cases pages might still end up on pcp lists and that would allow > * for their allocation even when they are in fact isolated already. Depending > - * on how strong of a guarantee the caller needs drain_all_pages might be needed > - * (e.g. __offline_pages will need to call it after check for isolated range for > - * a next retry). > + * on how strong of a guarantee the caller needs, further drain_all_pages() > + * might be needed (e.g. __offline_pages will need to call it after check for > + * isolated range for a next retry). > * > * Return: 0 on success and -EBUSY if any part of range cannot be isolated. > */ > Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb