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[2003:cb:c73c:f800:7df6:a2c9:652e:c799]) by smtp.gmail.com with ESMTPSA id k21-20020a05600c1c9500b00401e32b25adsm8558453wms.4.2023.10.30.01.00.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Oct 2023 01:00:57 -0700 (PDT) Message-ID: Date: Mon, 30 Oct 2023 09:00:56 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [v3 2/3] mm: Defer TLB flush by keeping both src and dst folios at migration To: Byungchul Park , linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: kernel_team@skhynix.com, akpm@linux-foundation.org, ying.huang@intel.com, namit@vmware.com, xhao@linux.alibaba.com, mgorman@techsingularity.net, hughd@google.com, willy@infradead.org, peterz@infradead.org, luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com References: <20231030072540.38631-1-byungchul@sk.com> <20231030072540.38631-3-byungchul@sk.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: <20231030072540.38631-3-byungchul@sk.com> 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-Rspam-User: X-Stat-Signature: 4bkrticym8p5e15yfqdpnoip5nks7d6m X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 56AA0C0020 X-HE-Tag: 1698652872-331165 X-HE-Meta: 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 VqYlo1QF EiyZyQmEX+AWxzaEcRiPhmZINzKwfjg4pW8FDxn/KjZe1nRQd5Q7D6VwMwiKZgNzqdHVnwH7nsmEjK2jyefSgtWOZtoqsvJlUQw7E4s3neMAffe8NCbwTLQOGVSilHV2muL7APOt2VyBfnQQcLzb6V/QJNOCpvafcQVvzb5tje2dDuHcy80QSTY47Dq0KgMZcjfpftQOcWSOVxJfi7pomhpQXxoa/HBnAEoPMBhMPeFgAlQLZIxayPCBssBlFx+O5vhE4MRo+SpMU9Phf6scGFXN7pZ3KuCQ81Dmt/zlKRbUMLPuCRzZCEunGUJqEpPfE2lsdXX4yntopTXBMFPRzVPvMUTclYRtiZXAX9TrNude0v/mapeHOEn0QbbSwtb5lLvIxGqOTt2dKJ1vQo3AQjxxx6db2M8PE5SDKFMPbih2bGM4= 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 30.10.23 08:25, Byungchul Park wrote: > Implementation of CONFIG_MIGRC that stands for 'Migration Read Copy'. > We always face the migration overhead at either promotion or demotion, > while working with tiered memory e.g. CXL memory and found out TLB > shootdown is a quite big one that is needed to get rid of if possible. > > Fortunately, TLB flush can be defered or even skipped if both source and > destination of folios during migration are kept until all TLB flushes > required will have been done, of course, only if the target PTE entries > have read only permission, more precisely speaking, don't have write > permission. Otherwise, no doubt the folio might get messed up. > > To achieve that: > > 1. For the folios that map only to non-writable TLB entries, prevent > TLB flush at migration by keeping both source and destination > folios, which will be handled later at a better time. > > 2. When any non-writable TLB entry changes to writable e.g. through > fault handler, give up CONFIG_MIGRC mechanism so as to perform > TLB flush required right away. > > 3. Temporarily stop migrc from working when the system is in very > high memory pressure e.g. direct reclaim needed. > > The measurement result: > > Architecture - x86_64 > QEMU - kvm enabled, host cpu > Numa - 2 nodes (16 CPUs 1GB, no CPUs 8GB) > Linux Kernel - v6.6-rc5, numa balancing tiering on, demotion enabled > Benchmark - XSBench -p 50000000 (-p option makes the runtime longer) > > run 'perf stat' using events: > 1) itlb.itlb_flush > 2) tlb_flush.dtlb_thread > 3) tlb_flush.stlb_any > 4) dTLB-load-misses > 5) dTLB-store-misses > 6) iTLB-load-misses > > run 'cat /proc/vmstat' and pick: > 1) numa_pages_migrated > 2) pgmigrate_success > 3) nr_tlb_remote_flush > 4) nr_tlb_remote_flush_received > 5) nr_tlb_local_flush_all > 6) nr_tlb_local_flush_one > > BEFORE - mainline v6.6-rc5 > ------------------------------------------ > $ perf stat -a \ > -e itlb.itlb_flush \ > -e tlb_flush.dtlb_thread \ > -e tlb_flush.stlb_any \ > -e dTLB-load-misses \ > -e dTLB-store-misses \ > -e iTLB-load-misses \ > ./XSBench -p 50000000 > > Performance counter stats for 'system wide': > > 20953405 itlb.itlb_flush > 114886593 tlb_flush.dtlb_thread > 88267015 tlb_flush.stlb_any > 115304095543 dTLB-load-misses > 163904743 dTLB-store-misses > 608486259 iTLB-load-misses > > 556.787113849 seconds time elapsed > > $ cat /proc/vmstat > > ... > numa_pages_migrated 3378748 > pgmigrate_success 7720310 > nr_tlb_remote_flush 751464 > nr_tlb_remote_flush_received 10742115 > nr_tlb_local_flush_all 21899 > nr_tlb_local_flush_one 740157 > ... > > AFTER - mainline v6.6-rc5 + CONFIG_MIGRC > ------------------------------------------ > $ perf stat -a \ > -e itlb.itlb_flush \ > -e tlb_flush.dtlb_thread \ > -e tlb_flush.stlb_any \ > -e dTLB-load-misses \ > -e dTLB-store-misses \ > -e iTLB-load-misses \ > ./XSBench -p 50000000 > > Performance counter stats for 'system wide': > > 4353555 itlb.itlb_flush > 72482780 tlb_flush.dtlb_thread > 68226458 tlb_flush.stlb_any > 114331610808 dTLB-load-misses > 116084771 dTLB-store-misses > 377180518 iTLB-load-misses > > 552.667718220 seconds time elapsed > > $ cat /proc/vmstat > So, an improvement of 0.74% ? How stable are the results? Serious question: worth the churn? Or did I get the numbers wrong? > #define node_present_pages(nid) (NODE_DATA(nid)->node_present_pages) > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 5c02720c53a5..1ca2ac91aa14 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -135,6 +135,9 @@ enum pageflags { > #ifdef CONFIG_ARCH_USES_PG_ARCH_X > PG_arch_2, > PG_arch_3, > +#endif > +#ifdef CONFIG_MIGRC > + PG_migrc, /* Page has its copy under migrc's control */ > #endif > __NR_PAGEFLAGS, > > @@ -589,6 +592,10 @@ TESTCLEARFLAG(Young, young, PF_ANY) > PAGEFLAG(Idle, idle, PF_ANY) > #endif > > +#ifdef CONFIG_MIGRC > +PAGEFLAG(Migrc, migrc, PF_ANY) > +#endif I assume you know this: new pageflags are frowned upon. -- Cheers, David / dhildenb