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infrastructure To: Bharata B Rao , Matthew Wilcox Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Jonathan.Cameron@huawei.com, dave.hansen@intel.com, gourry@gourry.net, mgorman@techsingularity.net, mingo@redhat.com, peterz@infradead.org, raghavendra.kt@amd.com, riel@surriel.com, rientjes@google.com, sj@kernel.org, weixugc@google.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, dave@stgolabs.net, nifan.cxl@gmail.com, xuezhengchu@huawei.com, yiannis@zptcorp.com, akpm@linux-foundation.org, david@kernel.org, byungchul@sk.com, kinseyho@google.com, joshua.hahnjy@gmail.com, yuanchu@google.com, alok.rathore@samsung.com, shivankg@amd.com, donettom@linux.ibm.com References: <20260504060924.344313-1-bharata@amd.com> <211a37f8-92a4-4e5a-9d55-b61b25f504a7@amd.com> Content-Language: en-US From: Balbir Singh In-Reply-To: <211a37f8-92a4-4e5a-9d55-b61b25f504a7@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: 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U2FsdGVkX18OJ618yCbUR8wouZCNxxO8CzOlGlTHz8rRROfB6y54amu/8KPGJV0S2Wr5xvHlE1J69pcv3+PIhFoHyjdotbVYv2Tn0tDnwLBFTPq6V5CboBp2m0UwYltY6sTGUE+Do336PSBCcSx7bnjNPhj8Bo9wOBHHZTfdSopV5UezABZ/slvIeQufIt5lK24hA/IMgc/2WOLcoEKsXLv6jwsKR1hvuJY5PsZHqQaOKrGhVHvhNe7iVHXrIjwol3lUhaPuPghYpOprXGS2IgXxKHG389TaUogF8+ILTaQou2raKB/tgG3wCxAt8OJpCrahNGFo1W409TzzBTSJD+BLEknC5tonlJ85ZVRPjBgyCgQkVMnYPfWlGgCSG2RgnioNzzD5ExjFkI7B+lt4LDn7PR0KEXtYNpfbqTBQFf5Lr1YpOhDWLOTX9RC+DjRoOJqZ/AHk6EbqRh/QCOWXP4g7xuVeD3AQYbJUq/7Klix4uKu8p0tf8OSOY+/JLEP9QyhykxXZLeigpw5QwcweduA+v8hzeYfq8ePrMvQZoWQnGzY4IU5HC5keziOUQ+1rWhp4X2YGGzU4aw1yJcKcWbn7xUCCnxeuoAbJY7og/PjNUi9OfxvMoeyruxh8Qw4p2zCg9DYBxtQdvm5lyRJCYKbJhVDwD2/DqYtR/3Wu4kjk+q3xCl3kCj82Asim2MJl9eulrhjDdjf6bXFLpv2YhkOd8o/lz19Kb4uzBj1Y44FMsGexMsFiuNoq3iPwkwLRvpBi7UXySqIYViUhZwCg9vCahVCFoVbUVh48dkKK9aMJ0VLYzPCiODi0B9fOvPcIpccr7bTokLomDJVv3VnsIC/h33SmFHwhKHCLplOujg8cAsl8wuMKf7TokDz56Hr2FwMUnQv+f/zue1YC2vjjLmpC6eUhcAlFsAPQ9LSlUPizvszlxFs6kT8oWjYWv8l1d62WVmLaClDt55qkeVf eFm6uvK0 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 5/6/26 13:43, Bharata B Rao wrote: > On 06-May-26 3:47 AM, Balbir Singh wrote: >> On 5/5/26 06:36, Matthew Wilcox wrote: >>> On Mon, May 04, 2026 at 11:39:17AM +0530, Bharata B Rao wrote: >>>> This is v7 of pghot, a hot-page tracking and promotion subsystem. The >>> >>> I continue to think we should not do this. >>> >> >> I am unclear about the benefits of the patchset, I have not tested >> it or reviewed the latest revision. My big concern was that top-tier >> might not always be suitable. > > So you are saying that we should have a capability to promote accessed pages > from lower tier to an other tier that is not classified as top tier? Is that > non-top tier node the one which generates accesses? > Yes, a top tier node could be CPU less for example. >> >> I see that there are some numbers posted, but I find this weird >> "After the graph creation, the processes are stopped and data is migrated >> to CXL node 2 before continuing so that BFS phase starts accessing lower >> tier memory." Why not allocate everything on CXL node 2? > > In the ideal scenario, the benefit is to see if any pages that land up on lower > tier get identified as hot and get promoted. That means we need to create an > over-committed scenario where the pages get demoted first. I have provided Why do the pages need to get demoted? Why not allocate them from the lower tier to show that promotion upwards is helpful > numbers from such cases in my previous versions. The problem with this case is > that the base hot page promotion (NUMAB2) hasn't shown any benefit at all with > my micro-benchmark - Ref: > https://lore.kernel.org/linux-mm/868004d8-bb8e-4800-9fdd-ade48e95fe3b@amd.com/ > > Same has been observed with redis-memtier benchmark - > https://lore.kernel.org/linux-mm/957f2242-56d4-4bf0-8aeb-9d60fbea8c8c@amd.com/ > > Instead what I am doing here is to take out demotion from the scenario but still > retain the access pattern of the benchmark by pushing out the data to lower tier > when the benchmark reaches steady allocation state. > Balbir