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[2003:cb:c721:b900:4f34:b2b7:739d:a650]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3718985a48asm4310368f8f.62.2024.08.16.13.12.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 16 Aug 2024 13:12:04 -0700 (PDT) Message-ID: <29d190d9-6b1a-409b-b3a1-90539ddbc091@redhat.com> Date: Fri, 16 Aug 2024 22:12:03 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: remove migration for HugePage in isolate_single_pageblock() To: Zi Yan , Kefeng Wang Cc: Andrew Morton , Oscar Salvador , linux-mm@kvack.org, Matthew Wilcox References: <20240816040625.650053-1-wangkefeng.wang@huawei.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW 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/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz 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+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/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 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 86A281C0020 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: e4nie3ekzpiho8srrguc5s7siu4bxsdu X-HE-Tag: 1723839129-988938 X-HE-Meta: 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 VNBvZ24v 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 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: List-Subscribe: List-Unsubscribe: On 16.08.24 17:06, Zi Yan wrote: > On 16 Aug 2024, at 7:30, Kefeng Wang wrote: > >> On 2024/8/16 18:11, David Hildenbrand wrote: >>> On 16.08.24 06:06, Kefeng Wang wrote: >>>> The gigantic page size may larger than memory block size, so memory >>>> offline always fails in this case after commit b2c9e2fbba32 ("mm: make >>>> alloc_contig_range work at pageblock granularity"), >>>> >>>> offline_pages >>>>    start_isolate_page_range >>>>      start_isolate_page_range(isolate_before=true) >>>>        isolate [isolate_start, isolate_start + pageblock_nr_pages) >>>>      start_isolate_page_range(isolate_before=false) >>>>        isolate [isolate_end - pageblock_nr_pages, isolate_end) pageblock >>>>             __alloc_contig_migrate_range >>>>            isolate_migratepages_range >>>>              isolate_migratepages_block >>>>                isolate_or_dissolve_huge_page >>>>                  if (hstate_is_gigantic(h)) >>>>                      return -ENOMEM; >>>> >>>> In fact, we don't need to migrate page in page range isolation, for >>>> memory offline path, there is do_migrate_range() to move the pages. >>>> For contig allocation, there is another __alloc_contig_migrate_range() >>>> after isolation to migrate the pages. So fix issue by skipping the >>>> __alloc_contig_migrate_range() in isolate_single_pageblock(). >>>> >>>> Fixes: b2c9e2fbba32 ("mm: make alloc_contig_range work at pageblock granularity") >>>> Signed-off-by: Kefeng Wang >>>> --- >>>>   mm/page_isolation.c | 28 +++------------------------- >>>>   1 file changed, 3 insertions(+), 25 deletions(-) >>>> >>>> diff --git a/mm/page_isolation.c b/mm/page_isolation.c >>>> index 39fb8c07aeb7..7e04047977cf 100644 >>>> --- a/mm/page_isolation.c >>>> +++ b/mm/page_isolation.c >>>> @@ -403,30 +403,8 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags, >>>>               unsigned long head_pfn = page_to_pfn(head); >>>>               unsigned long nr_pages = compound_nr(head); >>>> -            if (head_pfn + nr_pages <= boundary_pfn) { >>>> -                pfn = head_pfn + nr_pages; >>>> -                continue; >>>> -            } >>>> - >>>> -#if defined CONFIG_COMPACTION || defined CONFIG_CMA >>>> -            if (PageHuge(page)) { >>>> -                int page_mt = get_pageblock_migratetype(page); >>>> -                struct compact_control cc = { >>>> -                    .nr_migratepages = 0, >>>> -                    .order = -1, >>>> -                    .zone = page_zone(pfn_to_page(head_pfn)), >>>> -                    .mode = MIGRATE_SYNC, >>>> -                    .ignore_skip_hint = true, >>>> -                    .no_set_skip_hint = true, >>>> -                    .gfp_mask = gfp_flags, >>>> -                    .alloc_contig = true, >>>> -                }; >>>> -                INIT_LIST_HEAD(&cc.migratepages); >>>> - >>>> -                ret = __alloc_contig_migrate_range(&cc, head_pfn, >>>> -                            head_pfn + nr_pages, page_mt); >>>> -                if (ret) >>>> -                    goto failed; >>> >>> But won't this break alloc_contig_range() then? I would have expected that you have to special-case here on the migration reason (MEMORY_OFFLINE). >>> >> >> Yes, this is what I did in rfc, only skip migration for offline path. >> but Zi Yan suggested to remove migration totally[1] >> >> [1] https://lore.kernel.org/linux-mm/50FEEE33-49CA-48B5-B4C5-964F1BE25D43@nvidia.com/ >> >>> I remember some dirty details when we're trying to allcoate with a single pageblock for alloc_contig_range(). > > Most likely I was overthinking about the situation back then. I thought I'm more than happy if we can remove that code here :) > PageHuge, PageLRU, and __PageMovable all can be bigger than a pageblock, > but in reality only PageHuge can and the gigantic PageHuge is freed as > order-0. Does that still hold with Yu's patches to allocate/free gigantic pages from CMA using compound pages that are on the list (and likely already in mm-unstable)? I did not look at the freeing path of that patchset. As the buddy doesn't understand anything larger than MAX_ORDER, I would assume that we are fine. I assume the real issue is when we have a movable allocation (folio) that spans multiple pageblocks. For example, when MAX_ORDER is large than a single pageblock, like it is on x86. Besides gigantic pages, I wonder if that can happen. Likely currently really only with hugetlb. This means MIGRATE_ISOLATE pageblocks will get to the right > free list after __alloc_contig_migrate_range(), the one after > start_isolate_page_range(). > > David, I know we do not have cross-pageblock PageLRU yet (wait until > someone adds PMD-level mTHP). But I am not sure about __PageMovable, > even if you and Johannes told me that __PageMovable has no compound page. I think it's all order-0. Likely we should sanity check that somewhere (when setting a folio-page movable?). For example, the vmware balloon handles 2M pages differently than 4k pages. Only the latter is movable. > I wonder what are the use cases for __PageMovable. Is it possible for > a driver to mark its cross-pageblock page __PageMovable and provide > ->isolate_page and ->migratepage in its struct address_space_operations? > Or it is unsupported, so I should not need to worry about it. I never tried. We should document and enforce/sanity check that it only works with order-0 for now. > >>> >>> Note that memory offlining always covers pageblocks large than MAX_ORDER chunks (which implies full pageblocks) but alloc_contig_range() + CMA might only cover (parts of) single pageblocks. >>> >>> Hoping Zi Yan can review :) > > At the moment, I think this is the right clean up. I think we want to have some way to catch when it changes. For example, can we warn if we find a LRU folio here that is large than a single pageblock? Also, I think we have to document why it works with hugetlb gigantic folios / large CMA allocations somewhere (the order-0 stuff you note above). Maybe as part of this changelog. -- Cheers, David / dhildenb