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[2003:cb:c709:3400:5126:3051:d630:92ee]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4256b09abbfsm228112145e9.35.2024.07.03.01.40.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 Jul 2024 01:40:26 -0700 (PDT) Message-ID: Date: Wed, 3 Jul 2024 10:40:25 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/page_alloc: remove prefetchw() on freeing page to buddy system To: Wei Yang Cc: akpm@linux-foundation.org, linux-mm@kvack.org, willy@infradead.org References: <20240702020931.7061-1-richard.weiyang@gmail.com> <20240703001202.k4ebfpgcad3jwaev@master> 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: <20240703001202.k4ebfpgcad3jwaev@master> 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-Server: rspam11 X-Rspamd-Queue-Id: 6AD95160002 X-Stat-Signature: 774odpea9iwak8trpfyamhpieeyzwz5f X-Rspam-User: X-HE-Tag: 1719996031-265646 X-HE-Meta: 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 knk9huPC 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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 03.07.24 02:12, Wei Yang wrote: > On Tue, Jul 02, 2024 at 08:57:57AM +0200, David Hildenbrand wrote: >> On 02.07.24 04:09, Wei Yang wrote: >>> The prefetchw() is introduced from an ancient patch[1]. >>> >>> The change log says: >>> >>> The basic idea is to free higher order pages instead of going >>> through every single one. Also, some unnecessary atomic operations >>> are done away with and replaced with non-atomic equivalents, and >>> prefetching is done where it helps the most. For a more in-depth >>> discusion of this patch, please see the linux-ia64 archives (topic >>> is "free bootmem feedback patch"). >>> >>> So there are several changes improve the bootmem freeing, in which the >>> most basic idea is freeing higher order pages. And as Matthew says, >>> "Itanium CPUs of this era had no prefetchers." >>> >>> I did 10 round bootup tests before and after this change, the data >>> doesn't prove prefetchw() help speeding up bootmem freeing. The sum of >>> the 10 round bootmem freeing time after prefetchw() removal even 5.2% >>> faster than before. >> >> I suspect this is noise, though. >> >>> >>> [1]: https://lore.kernel.org/linux-ia64/40F46962.4090604@sgi.com/ >>> >>> Signed-off-by: Wei Yang >>> Suggested-by: Matthew Wilcox >>> CC: David Hildenbrand >>> >>> --- >>> The patch is based on mm-stable with David's change. >>> --- >>> mm/page_alloc.c | 13 ++----------- >>> 1 file changed, 2 insertions(+), 11 deletions(-) >>> >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index 116ee33fd1ce..c46aedfc9a12 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -1236,16 +1236,11 @@ void __meminit __free_pages_core(struct page *page, unsigned int order, >>> */ >>> if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG) && >>> unlikely(context == MEMINIT_HOTPLUG)) { >>> - prefetchw(p); >>> - for (loop = 0; loop < (nr_pages - 1); loop++, p++) { >>> - prefetchw(p + 1); >>> + for (loop = 0; loop < nr_pages; loop++, p++) { >>> VM_WARN_ON_ONCE(PageReserved(p)); >>> __ClearPageOffline(p); >>> set_page_count(p, 0); >>> } >> >> Something like: >> >> for (;;) { >> ... >> if (++loop >= nr_pages) >> break; >> p++; >> } >> > > So you prefer to have another version with this format? Sth like this? Whatever you prefer, just pointing it out that we can do slightly better :) -- Cheers, David / dhildenb