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[2003:cb:c717:a000:d4df:4b8f:37d4:59e4]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-35dd064998bsm1977446f8f.91.2024.05.31.07.32.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 31 May 2024 07:32:05 -0700 (PDT) Message-ID: <345161ac-3b42-48aa-ab3d-3b183316479a@redhat.com> Date: Fri, 31 May 2024 16:32:04 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/6] mm/zsmalloc: use a proper page type To: Matthew Wilcox , Sergey Senozhatsky Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Mike Rapoport , Minchan Kim , Hyeonggon Yoo <42.hyeyoo@gmail.com> References: <20240529111904.2069608-1-david@redhat.com> <20240529111904.2069608-4-david@redhat.com> <20240530050123.GA8400@google.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: 7bit X-Rspamd-Queue-Id: D5A5B1A0021 X-Stat-Signature: mfx47yo9n7mz4y5ysu3hi3g1h5o18fgd X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1717165930-239496 X-HE-Meta: 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 oC6Y1bUB 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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 31.05.24 16:27, Matthew Wilcox wrote: > On Thu, May 30, 2024 at 02:01:23PM +0900, Sergey Senozhatsky wrote: >> On (24/05/29 13:19), David Hildenbrand wrote: >>> We won't be able to support 256 KiB base pages, which is acceptable. >> [..] >>> +config HAVE_ZSMALLOC >>> + def_bool y >>> + depends on MMU >>> + depends on PAGE_SIZE_LESS_THAN_256KB # we want <= 64 KiB >> >> Can't really say that I'm happy with this, but if mm-folks are >> fine then okay. > > I have an idea ... > > We use 6 of the bits in the top byte of the page_type to enumerate > a type (ie value 0x80-0xbf) and then the remaining 24 bits are > available. It's actually more efficient: > > $ ./scripts/bloat-o-meter prev.o .build-debian/mm/filemap.o > add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-40 (-40) > Function old new delta > __filemap_add_folio 1102 1098 -4 > filemap_unaccount_folio 455 446 -9 > replace_page_cache_folio 474 447 -27 > Total: Before=41258, After=41218, chg -0.10% > > (that's all from PG_hugetlb) > > before: > 1406: 8b 46 30 mov 0x30(%rsi),%eax > mapcount = atomic_read(&folio->_mapcount) + 1; > 1409: 83 c0 01 add $0x1,%eax > if (mapcount < PAGE_MAPCOUNT_RESERVE + 1) > 140c: 83 f8 81 cmp $0xffffff81,%eax > 140f: 7d 6c jge 147d > 1411: 8b 43 30 mov 0x30(%rbx),%eax > 1414: 25 00 08 00 f0 and $0xf0000800,%eax > 1419: 3d 00 00 00 f0 cmp $0xf0000000,%eax > 141e: 74 4e je 146e > > after: > 1406: 8b 46 30 mov 0x30(%rsi),%eax > mapcount = atomic_read(&folio->_mapcount) + 1; > 1409: 83 c0 01 add $0x1,%eax > if (mapcount < PAGE_MAPCOUNT_RESERVE + 1) > 140c: 83 f8 81 cmp $0xffffff81,%eax > 140f: 7d 63 jge 1474 4> > if (folio_test_hugetlb(folio)) > 1411: 80 7b 33 84 cmpb $0x84,0x33(%rbx) > 1415: 74 4e je 1465 > > so we go from "mov, and, cmp, je" to just "cmpb, je", which must surely > be faster to execute as well as being more compact in the I$ (6 bytes vs 15). > > Anyway, not tested but this is the patch I used to generate the above. > More for comment than application. Right, it's likely very similar to my previous proposal to use 8 bit (uint8_t) for the type. https://lore.kernel.org/all/00ba1dff-7c05-46e8-b0d9-a78ac1cfc198@redhat.com/ I would prefer if we would do that separately; unless someone is able to raise why we care about zram + 256KiB that much right now. (claim: we don't) > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 5265b3434b9e..4129d04ac812 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -942,24 +942,24 @@ PAGEFLAG_FALSE(HasHWPoisoned, has_hwpoisoned) > * mistaken for a page type value. > */ > > -#define PAGE_TYPE_BASE 0xf0000000 > -/* Reserve 0x0000007f to catch underflows of _mapcount */ > -#define PAGE_MAPCOUNT_RESERVE -128 > -#define PG_buddy 0x00000080 > -#define PG_offline 0x00000100 > -#define PG_table 0x00000200 > -#define PG_guard 0x00000400 > -#define PG_hugetlb 0x00000800 > -#define PG_slab 0x00001000 > - > -#define PageType(page, flag) \ > - ((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE) > -#define folio_test_type(folio, flag) \ > - ((folio->page.page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE) > +/* Reserve 0x0000007f to catch underflows of _mapcount */ > +#define PAGE_MAPCOUNT_RESERVE -128 > + > +#define PG_buddy 0x80 > +#define PG_offline 0x81 > +#define PG_table 0x82 > +#define PG_guard 0x83 > +#define PG_hugetlb 0x84 > +#define PG_slab 0x85 Hoping we can stop calling that PG_ ... -- Cheers, David / dhildenb