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[2003:cb:c721:a000:7426:f6b4:82a3:c6ab]) by smtp.gmail.com with ESMTPSA id jg28-20020a05600ca01c00b004063cd8105csm6128004wmb.22.2023.11.24.07.37.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 24 Nov 2023 07:37:02 -0800 (PST) Message-ID: Date: Fri, 24 Nov 2023 16:37:01 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/4] mm/ksm: add ksm advisor To: Stefan Roesch Cc: kernel-team@fb.com, akpm@linux-foundation.org, hannes@cmpxchg.org, riel@surriel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20231028000945.2428830-1-shr@devkernel.io> <20231028000945.2428830-2-shr@devkernel.io> <8734wxsn4u.fsf@devkernel.io> 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: <8734wxsn4u.fsf@devkernel.io> 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: rspam09 X-Rspamd-Queue-Id: D301FC0011 X-Stat-Signature: fp4xt8c9dgdod87bznwm9t49g3niawme X-Rspam-User: X-HE-Tag: 1700840226-313417 X-HE-Meta: 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 NIEoZ2n5 eYqp5LLrlSqhMujUQKgvC2CmSalxmlPmqJbTecIhFzzfzPaHTHET7dG5CcNZmiyexmdQbHvzFVJeXTpKplqWRAoFsTBPvgVLX3VQf+H2G5gp6Cpd1GCBShWy8PljR2NSylPwZseC785NexQoJPlkvc3qa7awWTT35u7j6sJ1oLiOOOpYzs7zgKu6kHE2qsV6X2VlHD/KmFbslXZ5qx+9GG61d7lXXcst3ojfPhkf1WREZKakN2e3TlF3UH40K2jaRftAgAiJ/zoJJa8yELLbEdEMs9V/YwKXaWrySgV52nb3Ha4MFvcaXBLI3G0qmCFynvVePcEo0hWGKfLC7XpwXEBh3L2HY/b40HoUDwis5r9FaBmwAFwr7H6qFrZRqnkrHeBkB2ICbmfzG/yopM7ubdkltmCa5xjbxerlE 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: >> > > The min cpu case is to make sure that we scan fast enough to be able to > react fast enough to the changes in the number of pages. This helps in > determining in how quick we want to react to changes. This helps > especially with the startup phase of applications. > > We can certainly only set a default value, that is not exposed in sysfs. Less toggles is better. So if we can just use some sane starting default, that would be great. > >>> +/** >>> + * struct advisor_ctx - metadata for KSM advisor >>> + * @start_scan: start time of the current scan >>> + * @scan_time: scan time of previous scan >>> + * @change: change in percent to pages_to_scan parameter >>> + * @cpu_percent: average cpu percent usage of the ksmd thread for the last scan >>> + */ >>> +struct advisor_ctx { >>> + ktime_t start_scan; >>> + unsigned long scan_time; >>> + unsigned long change; >>> + unsigned long long cpu_time; >>> +}; >>> +static struct advisor_ctx advisor_ctx; >>> + >>> +/* Define different advisor's */ >>> +enum ksm_advisor_type { >>> + KSM_ADVISOR_NONE, >>> + KSM_ADVISOR_FIRST = KSM_ADVISOR_NONE, >> >> Unused, better drop it. 0 is the implicit first one. >> > Will change it accordingly. > >>> + KSM_ADVISOR_SCAN_TIME, >>> + KSM_ADVISOR_LAST = KSM_ADVISOR_SCAN_TIME >> >> Instead of "_LAST", maybe use "_COUNT" and use that when checking for valid >> values. >> >> But: we likely want to store "strings" instead of magic numbers from user space >> instead. >> > > Any recommendation for the naming of the parameters when I switch to > strings? Probably just "none" and "scan-time" ? >>> +} >>> + >>> +static void run_advisor(void) >>> +{ >>> + if (ksm_advisor == KSM_ADVISOR_SCAN_TIME) { >>> + s64 scan_time; >>> + >>> + /* Convert scan time to seconds */ >>> + scan_time = ktime_ms_delta(ktime_get(), advisor_ctx.start_scan); >>> + scan_time = div_s64(scan_time, MSEC_PER_SEC); >>> + scan_time = scan_time ? scan_time : 1; >>> + >>> + scan_time_advisor((unsigned long)scan_time); >>> + } >> >> We could have rescheduled in the meantime, right? Doesn't that mean that our CPU >> load consumption might be wrong in some cases? >> > Does it matter? I'm interested how long it takes to complete the scan, > including any scheduling. But isn't this also required to compute CPU load, so you can stay between min-load and max-load? - ksm_advisor_min_cpu (minimum value for cpu percent usage) - ksm_advisor_max_cpu (maximum value for cpu percent usage) Likely, you want to exclude any rescheduling from there? I'll have to recheck the logic. -- Cheers, David / dhildenb