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Wed, 04 Jan 2023 11:10:49 -0800 (PST) Received: from [10.67.48.245] ([192.19.223.252]) by smtp.googlemail.com with ESMTPSA id b66-20020a636745000000b0047702d44861sm20353041pgc.18.2023.01.04.11.10.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Jan 2023 11:10:47 -0800 (PST) Message-ID: Date: Wed, 4 Jan 2023 11:10:42 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: [PATCH v3 0/9] mm: introduce Designated Movable Blocks Content-Language: en-US To: Mel Gorman , Doug Berger Cc: Andrew Morton , Jonathan Corbet , Mike Rapoport , "Paul E. McKenney" , Neeraj Upadhyay , Randy Dunlap , Damien Le Moal , Muchun Song , Vlastimil Babka , Johannes Weiner , Michal Hocko , KOSAKI Motohiro , Mike Kravetz , David Hildenbrand , Oscar Salvador , Joonsoo Kim , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20221020215318.4193269-1-opendmb@gmail.com> <20221026105500.n6ddzqqf5ozjswsp@suse.de> <9842ee9c-5fcc-5458-2779-ad9b88468b48@gmail.com> <20221118170510.kexdiqsfaqwledpm@suse.de> <342da4ea-d04a-996c-85c4-3065dd4dc01f@gmail.com> <20230104153724.mormtuefwaiojvqt@suse.de> From: Florian Fainelli In-Reply-To: <20230104153724.mormtuefwaiojvqt@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 4834F4000A X-Rspamd-Server: rspam01 X-Stat-Signature: 4i91fpqs4s4n5qo85jgffpr5jyok37mm X-HE-Tag: 1672859451-440841 X-HE-Meta: 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 L8rOk1vZ /C/64am0BLTqEvKtqyJhpYE9snWMGMfjamB6BoU6tOXZcRSg3UkWoROSx6LvWN6FzyeOoMBPs17tgy8mwhZgYx0REw3GbxKTER66kCCEvm5fVq+FndppQ+ulaFA== 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: On 1/4/23 07:43, Mel Gorman wrote: [snip] >> What is of interest to Broadcom customers is to better distribute user space >> accesses across each memory controller to improve the bandwidth available to >> user space dominated work flows. With no ZONE_MOVABLE, the BCM7278 SoC with >> 1GB of memory on each memory controller will place the 1GB on the low >> address memory controller in ZONE_DMA and the 1GB on the high address memory >> controller in ZONE_NORMAL. With this layout movable allocation requests will >> only fallback to the ZONE_DMA (low memory controller) once the ZONE_NORMAL >> (high memory controller) is sufficiently depleted of free memory. >> >> Adding ZONE_MOVABLE memory above ZONE_NORMAL with the current movablecore >> behavior does not improve this situation other than forcing more kernel >> allocations off of the high memory controller. User space allocations are >> even more likely to be on the high memory controller. >> > > But it's a weak promise that interleaving will happen. If only a portion > of ZONE_MOVABLE is used, it might still be all on the same channel. This > might improve over time if enough memory was used and the system was up > for long enough. It is indeed a weak promise for user-space allocations out of ZONE_MOVABLE, however the other consumer of the DMB region is a kernel driver (typically a video decoder engine) which is directly tied to a specific memory controller/DMB region. For the kernel driver using the DMB region there is a hard guarantee from the kernel that it gets memory from a specific PFN range mapping directly to the desired memory controller and thus it is meeting the desired bandwidth allocation/deadlines/bursts etc. We care about both sides of the coin, though we acknowledge that "controlling" where user-space allocations are coming from such that they be steered towards a specific memory controller is a much harder task and so having some amount of non-determinism is acceptable here. -- Florian