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[2003:cb:c74b:ca00:4ca2:ff2c:9092:f070]) by smtp.gmail.com with ESMTPSA id e10-20020adffd0a000000b003334675634bsm10885476wrr.29.2023.12.12.05.44.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 12 Dec 2023 05:44:05 -0800 (PST) Message-ID: <9f81f89f-c3ad-4cef-a619-ad36348c8ef5@redhat.com> Date: Tue, 12 Dec 2023 14:44:04 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/4] mm/ksm: add ksm advisor To: Stefan Roesch , kernel-team@fb.com Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, riel@surriel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20231204234906.1237478-1-shr@devkernel.io> <20231204234906.1237478-2-shr@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: <20231204234906.1237478-2-shr@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-Queue-Id: A1935A0006 X-Rspam-User: X-Stat-Signature: r5idnm8btqho15cgcur9g5t833njtay8 X-Rspamd-Server: rspam03 X-HE-Tag: 1702388668-216140 X-HE-Meta: U2FsdGVkX19bZ29ao46kQqz8GtIoaksdsvYUHCKPetDZqTW4jvcQLdvGymmKGOIBjkt2JRzVnIuU69pbWJKs9fGb2WDap1igey1eY0Xnw+uZYnoGHXJZ/L4gYhpkwlua85i/As/ge39/VY/+wVtnn976lX/v7aOZiHQBO4qy4US7JdmsgmeSk4jKAmT0+w7aYzoWqhfg4sMTZP2ABtoBB4/fF2b4tg/LqvBvn+pPVrL0/PgQVE//wOeU6GO/N9A9mI7txyF5NCQ2wptCzURZnL4xgldz6KeE0I4g2kKvLoZWn3HDTCbUNxJDXO9oIPXr6veXqg9D6Hapd8CkQDsK7gP5y3ey3Kr9OI6y0t/TURFMxdySmwXdQtYEAlKd3EPvuFDFqDrkpWULcAXkYlkt52gr7RXjppFDxG5N2Q+JJSeygBpYm4RPuWxn09YPeB/p4pe280RRLE1tFMr+d3KOOsWj0fvjbaMvEUn7Y6LIOrtZnbN2VJIqvOe4LMZdLT638jSWIBfyhSfkbYclFWmzSKdf46H6FJ+Rp0h8CLEXSeE7fRokc/5CFp5J/Zfur+I9dApPG84vSm+/wGi6x8Dpl/ZjWS0q9r0RaqZxPoCD/Vnf1V2eEdeeBhWxFjuebfdFF/+svoLxi4HZp3nkbOUfxTZYP0FHA4AQfDu3Cjg3jehfPZFIPBq+7+PWlFbD0vXCQ5r9lR2f4zZm7gy8k15UYpp8lhTw7UX/WduKvg72it8b2zT4vG5vcQomOQt6TyNUWDQZXmGLS6IZ40qCMI3nZf9kXn3+2bFgAKP2f0YEdQmhAg/M13sILWGqert659TlYVDEmZRIU/5tddj+Pasqchi8XB8WVikQU9n8ZpL9yrNjhsBGXIG8ePArcd6asdqITF9ciXVzU8M7JKiy7FUeUwj8Vh8/LUuBJW8YG0DiUHvHy1GaC6iaVxETo+yGADM0LRgSsV22I73BudpZYa5 95Qtm07Y I/sE2wbgEqWVtEpjLdZFx56Ll/l4bldM9xtcEshoDB+THz80LG8dV2lzj+2E83cVbVHu5OTazH3AIIoeGFiL4bj2vS3rKi4pHB6zRYVqdniXa+jMtX4g929bxPyGVh2EDt77ariA2GeMefACO7+a9md8xQfvnuACpqka/L1ngOeGJnAouUlKWHHDfKO3zIdtoFfnh0DnsjgNNluNw2MNUWeF+JJIEnNulvwVIezo+N5txhE+3qXDMOR0ef0ipQ+W5EmJgD1lP+/mrkVtKiW6Jhws8RXK6Njuq/tIrN/dfYryvj2ExJjlQlvnb9iv7+/X5aV7KvUGax/U3Jhy7dKVu6zS/4WJZNRk9cjvS46ePtEPGqpNhBPSfnw0x69a0TVarOxItA1D6vzo/C7RUfaseq+jNJrrzmpzUMFGhUmi8DH9GcOL0RE8pWvU1jWjanwC+SA9e 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: [...] > + > +/** > + * 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_time: cpu time consumed by the ksmd thread in the previous 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_SCAN_TIME, > +}; > +static enum ksm_advisor_type ksm_advisor; > + > +static void init_advisor(void) > +{ > + advisor_ctx = (const struct advisor_ctx){ 0 }; > +} Again, you can drop this completely. The static values are already initialized to 0. Or is there any reason to initialize to 0 explicitly? > + > +static void set_advisor_defaults(void) > +{ > + if (ksm_advisor == KSM_ADVISOR_NONE) > + ksm_thread_pages_to_scan = DEFAULT_PAGES_TO_SCAN; > + else if (ksm_advisor == KSM_ADVISOR_SCAN_TIME) > + ksm_thread_pages_to_scan = ksm_advisor_min_pages; > +} That function is unused? > + > +static inline void advisor_start_scan(void) > +{ > + if (ksm_advisor == KSM_ADVISOR_SCAN_TIME) > + advisor_ctx.start_scan = ktime_get(); > +} > + > +static inline s64 advisor_stop_scan(void) > +{ > + return ktime_ms_delta(ktime_get(), advisor_ctx.start_scan); > +} Just inline that into the caller. Then rename run_advisor() into advisor_stop_scan(). So in scan_get_next_rmap_item)( you have paired start+stop hooks. > + > +/* > + * Use previous scan time if available, otherwise use current scan time as an > + * approximation for the previous scan time. > + */ > +static inline unsigned long prev_scan_time(struct advisor_ctx *ctx, > + unsigned long scan_time) > +{ > + return ctx->scan_time ? ctx->scan_time : scan_time; > +} > + > +/* Calculate exponential weighted moving average */ > +static unsigned long ewma(unsigned long prev, unsigned long curr) > +{ > + return ((100 - EWMA_WEIGHT) * prev + EWMA_WEIGHT * curr) / 100; > +} > + > +/* > + * The scan time advisor is based on the current scan rate and the target > + * scan rate. > + * > + * new_pages_to_scan = pages_to_scan * (scan_time / target_scan_time) > + * > + * To avoid pertubations it calculates a change factor of previous changes. s/pertubations/perturbations/ Do you also want to describe how min/max CPU comes into play? > + * A new change factor is calculated for each iteration and it uses an > + * exponentially weighted moving average. The new pages_to_scan value is > + * multiplied with that change factor: > + * > + * new_pages_to_scan *= change facor > + * > + * In addition the new pages_to_scan value is capped by the max and min > + * limits. > + */ With that, LGTM Acked-by: David Hildenbrand -- Cheers, David / dhildenb