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[2003:cb:c736:ca00:b4c3:24bd:c2f5:863c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-438bd4fa463sm137649125e9.8.2025.01.27.08.09.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Jan 2025 08:09:58 -0800 (PST) Message-ID: Date: Mon, 27 Jan 2025 17:09:57 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Direct I/O performance problems with 1GB pages To: Matthew Wilcox Cc: linux-mm@kvack.org, linux-block@vger.kernel.org, Muchun Song , Jane Chu , Andres Freund References: 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-MFC-PROC-ID: ypL0CbPiqjoCu2-7e4IIYR5n8knl3t1Wu6xVFL5i4oQ_1737994200 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 903364000F X-Stat-Signature: pyrw8ko149u6i1ipoo6ggid4k5jsys1j X-HE-Tag: 1737994204-771088 X-HE-Meta: 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 lSCXAnmP wZIfdgB+Z+yTtLP4kc5nDMLlc8HfQByBf/B5xsCHhINunciDLNdlAzKMA528qe0HNsE4hhACu1odR+7fPPY32Tx4IAvSeJOVyzX52boeN29OrOHND5H/Il7JnrwA+bhHxdfSdDHJc4MIcmQrEvrHALQdUkvkyMYVXp4fmX6K6ScEXvTOaiv2L/ZJ+tICVmjSbvbTzdpUkpSBmsJ8KgEOSTgEOf40Y8/5ZlU/WgogMUcJv52VpSozUbUgwvlPfRAGQe82KqvTPtxXg+LOXxoyvu4yIFnPV2MXfk9UBuVQJvx4Rt+zVdxWieZqzBysQW0058MnUAii8oJtflfX21E4ifv/ZGXYgXVWy/jdZu0ZFPpygZ4j0yi0tRa27ClI9V1HwDZ8W169+WXyoIxc= 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: > >> If the workload doing a lot of single-page try_grab_folio_fast(), could it >> do so on a larger area (multiple pages at once -> single refcount update)? > > Not really. This is memory that's being used as the buffer cache, so > every thread in your database is hammering on it and pulling in exactly > the data that it needs for the SQL query that it's processing. Ouch. > >> Maybe there is a link to the report you could share, thanks. > > Andres shared some gists, but I don't want to send those to a > mailing list without permission. Here's the kernel part of the > perf report: > > 14.04% postgres [kernel.kallsyms] [k] try_grab_folio_fast > | > --14.04%--try_grab_folio_fast > gup_fast_fallback > | > --13.85%--iov_iter_extract_pages > bio_iov_iter_get_pages > iomap_dio_bio_iter > __iomap_dio_rw > iomap_dio_rw > xfs_file_dio_read > xfs_file_read_iter > __io_read > io_read > io_issue_sqe > io_submit_sqes > __do_sys_io_uring_enter > do_syscall_64 > > Now, since postgres is using io_uring, perhaps there could be a path > which registers the memory with the iouring (doing the refcount/pincount > dance once), and then use that pinned memory for each I/O. Maybe that > already exists; I'm not keeping up with io_uring development and I can't > seem to find any documentation on what things like io_provide_buffers() > actually do. That's precisely what io-uring fixed buffers do :) -- Cheers, David / dhildenb