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Sat, 18 Jul 2026 15:19:59 -0700 (PDT) Received: from [2a00:79e0:2eb4:9:5365:2f3e:9da8:d323] ([2a00:79e0:2eb4:9:5365:2f3e:9da8:d323]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2cf346da07csm32012185ad.52.2026.07.18.15.19.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 18 Jul 2026 15:19:59 -0700 (PDT) Date: Sat, 18 Jul 2026 15:19:58 -0700 (PDT) From: David Rientjes To: Davidlohr Bueso , Fan Ni , Frank van der Linden , Gregory Price , Jonathan Cameron , Joshua Hahn , Raghavendra K T , "Rao, Bharata Bhasker" , SeongJae Park , Wei Xu , Xuezheng Chu , Yiannis Nikolakopoulos , Zi Yan cc: linux-mm@kvack.org Subject: [Linux Memory Hotness and Promotion] Notes from July 16, 2026 Message-ID: <6e07d152-d746-ad9d-9426-bf51647338d0@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: AE0F840005 X-Stat-Signature: hypid4ixjbwocp87qr78aaw81fgw8ooa X-HE-Tag: 1784413201-54482 X-HE-Meta: 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 E1BhXYnN 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi everybody, Here are the notes from the last Linux Memory Hotness and Promotion call that happened on Thursday, July 16. Thanks to everybody who was involved! These notes are intended to bring people up to speed who could not attend the call as well as keep the conversation going in between meetings. ----->o----- Yiannis updated offline that he'll work on getting his non-temporal stores patch series on the upstream mailing list in the next couple of weeks. Huan also noted that would attend the next meeting to discuss the progress on memory error handling for NT stores. Wei noted that ARM memcpy should not need this support, but Jonathan suggested that there actually were specific instructions for this on ARM although all implementations may not actually use it[1]. ----->o----- We discussed LPC in Prague for October 5-7. The list of microconferences was available on the website[2], there are both "device memory" conferences as well as general MM. Shivank noted that he and Zi were collaborating on page migration offloads as well as rmap walk batching. He is also proposing simplification of migrate_pages() and the ABIs around that, including context information. I was concerned that we'd be delayed until LPC to make forward progress on this, Shivank was actively working on this. Joshua noted that he had discussed tier-aware memcg limits at LSF/MM/BPF so probably won't have a ton of new content for LPC. Jonathan suggested we may want to have a BOF simply for memory hotness and promotion work, similar to what we talk about in this call. ----->o----- Bharata updated on the status of his patch series. He now is working on finalizing v8 of the series that includes bug fixes. There are some behavioral changes that support NUMAB better and more closely support that implementation. He is collecting numbers on the patch series and, if there are no issues, then he will send the series upstream next week. He is also working on supporting for the second instance of IBS that is specific to memory access information. This will also be included in the v8 series to be sent upstream. ----->o----- Shviank updated on his series of changes for migrate_pages(), now at v6 upstream. He is continuing to post as an RFC for now and has addressed Sashiko review and feedback from David Hildenbrand. Teja Vojjala had been testing on Zen3 hardware for PTDMA and has been able to reproduce Shivank's numbers. He had observed many context switches, however, and suggested we should be able to optimize this. He asked Shivank if there has been testing done on SDXI. Shivank confirmed this and said that he can provide a patch to Teja for testing. I asked how the feedback should be provided, Shivank suggested feedback on the upstream mailing list would show more interest in it and we should likely pivot toward the SDXI use case. I suggested to Teja that we should be able to product a list of blockers that are preventing us from productizing this support so we can iterate through them and get on a path to using these in production. Teja asked if PTDMA is a legitimate use case and it is, but Shivank suggested focusing on future platforms with SDXI. ----->o----- Joshua sent out his latest series of tier-aware memcg limits to me and he wanted to do more testing before sending it out to the upstream list again. I noted that we will try to find two engineers to look over the patch series and provide feedback on the API and overall support, as well as any potential gaps that we see based on prodution use cases. I'm especially interested in any blockers that would prevent us from productionizing this. ----->o----- Gregory noted he was investing time in looking at how to optimize demotions and possible LRU inversions. Once a lower tier becomes full and there's memory pressure on the system, we start demoting to an even lower tier directly. He's been looking into better LRU ordering. He is continuing to work on this and will send it out to this group when ready. ----->o----- Next meeting will be on Thursday, July 30 at 8:30am PDT (UTC-7), everybody is welcome: https://meet.google.com/jak-ytdx-hnm Topics for the next meeting: - update on Yiannis's RFC for non-temporal stores enlightenment in migrate_pages() + update on Huan's support for memory error handling for NT stores - v8 of Bharata's patch series, including new IBS memory profiler support and benchmark numbers that were collected - v6 of Shivank's series for enlightening migrate_pages() for hardware assists and how this work will be charged to userspace, including for memory compaction, and separating the first patches out into a non-RFC series - v2 of tier-aware memcg limits, including ABI changes to support more than two tiers - Gregory's investigation into demotions for multi-tiered systems and LRU inversions - first class support for virtualization based memory tier support, how to leverge memory tiers in the guest - discuss generalized subsystem for providing bandwidth information independent of the underlying platform, ideally through resctrl, otherwise utilizing bandwidth information will be challenging + preferably this bandwidth monitoring is not per NUMA node but rather slow and fast Please let me know if you'd like to propose additional topics for discussion, thank you! [1] https://developer.arm.com/documentation/ddi0602/2021-09/Base-Instructions/CPYPWN--CPYMWN--CPYEWN--Memory-Copy--writes-non-temporal- [2] https://lpc.events/event/20/contributions/?config=c513701b-9743-4b41-914c-c1f29ee2307f