From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A1A99C61DD6 for ; Sat, 29 Aug 2026 21:48:37 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 370FC6B0088; Sat, 29 Aug 2026 17:48:36 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 321A56B008A; Sat, 29 Aug 2026 17:48:36 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 20F566B008C; Sat, 29 Aug 2026 17:48:36 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id DC9DA6B0088 for ; Sat, 29 Aug 2026 17:48:35 -0400 (EDT) Received: from smtpin28.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 4369E1201D8 for ; Sat, 29 Aug 2026 21:48:35 +0000 (UTC) X-FDA: 85155646590.28.AD65145 Received: from mail-pl1-f170.google.com (mail-pl1-f170.google.com [209.85.214.170]) by imf07.hostedemail.com (Postfix) with ESMTP id 9252140003 for ; Sat, 29 Aug 2026 21:48:33 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=google.com header.s=20251104 header.b=uCDCCpJU; spf=pass (imf07.hostedemail.com: domain of rientjes@google.com designates 209.85.214.170 as permitted sender) smtp.mailfrom=rientjes@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788040113; b=l5MBFbetXDcxfnRW/HmTizNrz+MrpYNnoNWTD6F+hzBvoR8By3Y3zLEU7uw9cZOuqfgR8C kkkBzTG8dnebRhgKAlj4/UxXbJ+QGpRX2J8lZxLANwZhv+M2VmYna8hqT7r/2oBEfaKuN+ kxDdu6A3X/X7/wvwmaCNhDoefWcI/cM= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=google.com header.s=20251104 header.b=uCDCCpJU; spf=pass (imf07.hostedemail.com: domain of rientjes@google.com designates 209.85.214.170 as permitted sender) smtp.mailfrom=rientjes@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788040113; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding:in-reply-to: references:dkim-signature; bh=NIfPECdOC7+2I+bBH3nhv6b9o46APH+A8u/7CKah76U=; b=VYlQiObsEobwiDKHBuySLxHFHD/VTu4LljsahyaldOWsXAlzImTkh1N6VGgrKS4Sl69amu XPDqr+FlRplt4Jf7cQgRMuJxB/2bwf7dK4cIbj//KB7GcfkjRGVMgMD4C6R07wDzoBruQV vSn9Jpb+eWMrY6hl5ybOdeT3s4WJNzE= Received: by mail-pl1-f170.google.com with SMTP id d9443c01a7336-2d8facae850so17735ad.0 for ; Sat, 29 Aug 2026 14:48:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1788040112; x=1788644912; darn=kvack.org; h=content-type:mime-version:message-id:subject:cc:to:from:date:from :to:cc:subject:date:message-id:reply-to:content-type; bh=NIfPECdOC7+2I+bBH3nhv6b9o46APH+A8u/7CKah76U=; b=uCDCCpJUUyLrQz7Qh3E9nYOS2Km6pJ/W4f9AiiRLvCNRkWW/HhYnjeSxTHG5TvIKAu r7oOub2ES2ODm14j1akAhzLRdVGjR0oX7f6ThMK5KtN9KQ5aHt3CPw+g/NxfHh8x/xch bGpO3foe9YXlxH9XXzf0z1bp4+W5aH7V/EzlekrPJsbFHDrw6rBkqu7ovgIZSnq6E2FD TSPASslKHjKZi8adgvDfHaS94ofPVH35SM0i8V6dG8f9moxDi0PXN+w+fsHfZjO5qO6o bdaM9DfR656DkMtsURRHkqyGD0y7I1Rax/fcvcSBI9ILxpd90v8VNZk/w2ewYkj3/k81 +B2A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1788040112; x=1788644912; h=content-type:mime-version:message-id:subject:cc:to:from:date :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to:content-type; bh=NIfPECdOC7+2I+bBH3nhv6b9o46APH+A8u/7CKah76U=; b=Qj36LE4wmF63FiegoYPOroTk0DC4TN2ppZ856cncw5kSuq9xsizUV08p0rsx8gn77/ dnnkqSLWfpkzHa8Lpd5gNNLkDNMXJIyOOde2FYjA9gu4Te+TGOjEE5KOoqJAFj5gO922 HQhO98ybV5wEJLJm6Dz1BSZk7kDfdl8enJ1JGBC9D2/Ljq/giv7JvHRqW8psA29ywG3+ AyUIxeWEgBqW/98U7f+UdWc3h/oTJoogmpHQcT7GMsDQYOas+96vAjhYJ8N9G1RcnUaT gHmndwAPM8mVOlMiRiDxIRf6mEY1eW8yA5ThVTNdixGi+xZhHp6+0LvypW41w+OMQKh1 PvIw== X-Gm-Message-State: AFuF++koxHgjkclnhcw4mWgiRog9dYvTdB+ephORdPXtrl9JLyg0/zzm MONDdhbr9NAVBRtzsT0MvhbgVyWMuyP3gqvM0Cjvj+QNMqt3UBBOxfIDQUy0NiXOXQ== X-Gm-Gg: AYBFou2PvUJRZ5BiL/6SOgl9uszQKg5MBCX+8xaDdHFAkNJonEkd8OckYTKeuAJG46G cDR9QlZCSFTfpfykDBZ0Rrb924zvKipsXYQu8blmWLMC0+oKfJjVcQQKHyRfPXfTAr2hRXvJwg+ 84Eva7jDZ8433L1rQkcVe0BiSzWIVUZZHxKq50RggusO6ezizfNTnPLgWEo1o8DxGC2vwVLrD/e UMhbvoUMJUp3w9s1uW1azxOY2oJLSleZsnrhnd6LJNANc4Nlm1fnecv4DsdGAVBazR0+QeKFgZK goIIq1EpDWVB0EAcCM9+BETsh+xpTSlr+gAJ2oeNlOirNZQMBtH0MCu4vl1M6b3avm6d1d4N7Cn d5+rZ6+nFT90nZXSGDBqH3JkBnxmTRX95St5tpASmz+rK1Vwe/u+6MTP5YPL6M+Fn28eEs9DGrV peHAPMrXbiWWw9dxlY3lA8PjAH9S0KUNtUUtqY0sxmPwDHZpdYuU1nbC5NUhZbsFCQypuol9e1g ViOeJz+ybtmmXhQj59Ba5Czfm0wjCHHcYtkhlN4UaHVG+BiRRb1fief/NFHa0TA+vBJTKqGYWxd W/A89YLhu7mBmwg= X-Received: by 2002:a17:902:f642:b0:2d5:db38:800f with SMTP id d9443c01a7336-2d8df554483mr5357385ad.14.1788040111466; Sat, 29 Aug 2026 14:48:31 -0700 (PDT) Received: from [2a00:79e0:2eb4:9:201d:c4fa:f5f8:451f] ([2a00:79e0:2eb4:9:201d:c4fa:f5f8:451f]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-398a661a0ddsm1530877a91.3.2026.08.29.14.48.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 29 Aug 2026 14:48:30 -0700 (PDT) Date: Sat, 29 Aug 2026 14:48:30 -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 August 27, 2026 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Stat-Signature: s4p54erxcynikk11g791tu94emmyq9qm X-Rspamd-Queue-Id: 9252140003 X-Rspamd-Server: rspam06 X-HE-Tag: 1788040113-719419 X-HE-Meta: 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 OM4MRCgz APbN6Eqlmww1660lSNe720SILlTH45rWRBmtapApC/nK9vUtfOXp9tt7uctx737YSiRzdwaUf3WtX07RZ3RxylTvai+CVC6NCYIpTC5FLUvRUkEuVNRepZUK7q9toeMnBJop4cf4Mz73EyubTBi2RmlPFYVB0lsichzTgsMZBHEhwSs62+6urAMbw4XxE1qs8HXK4SqmX/e4oHv/+F7gDP6Z+9IGAM7JUJOWYM9jovrMxFqdEx/QlWJUw3r4ggd+3VU7GOMWXUSnMrAzwsHcwqUOpmYXwAYhwkLr7nSpFtpV+E3Dj/yVGAWdZg/i8MjYqq8nweMjUzIAXfvEhcsUkeUYJifHhe5VPns1N7be9XXUYm+hT7xzrNEs1WplBbMHSL3SZPNF1wJRpVBTxR8gOjyqqK6484YfThIGCm1RpE8BRGGjN+7OA8MYkNg== 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, August 27. 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----- While Yiannis is on leave, I noted that Huan from Google would pursue sending the non-temporal stores patches upstream that include his extensions for handling of memory errors. They will sync together before the upstream posting. ----->o----- Bharata updated that he is getting ready for pghot v9. There were a lot of corner cases addressed in preparation for this. He also tried to compare DAMON with pghot and was able to get some realistic DAMON configuration working after some iterations. He posted some initial comparison numbers and more will follow in the pghot v9 posting. He's also planning on sepraating out the pghot-hwhints (IBS Memory Profiler source) into a separate patch series. Hrushikesh is working on reviving the PTE A bit based source (kscand) that Raghu worked on earlier; the plan is to integrate it into pghot, get benchmark results, and then post it. Bharata continued to request additional patch review from the group and any insight into relevant benchmarks would be very useful. ----->o----- Shivank noted that there were no new updates at this point for his migrate_pages() series because work was being done on the rmap series. He is waiting for additional feedback upstream and preparing for a discussion at LPC. He is also focused on migrate_pages() refactoring to make this cleaner, including for pending batching optimizations. Teja discussed hardware errors that were being encountered in his testing of SDXI, he was not yet able to get pages to be migrated. He is iterating on this with AMD and will continue conversations next week to try to make forward progress. ----->o----- Wei Xu suggested we add an additional topic for this meeting series: compression enlightenment for memory tiered architectures. He was advocating for a unified approach upstream for handling of second tier compression. Specifically, he was looking at software support for efficiency such as handling of free memory -- the goal is to represent this with no memory footprint in the second compressed tier. This would likely require hardware signals to indicate. Secondly, he noted that the physical capacity of memory on the second tier may be insufficient if the compression ratio is not good; we want to ensure that we do not run out of memory in these cases perhaps with watermark handling. He also noted that handling MCEs for compression support does not have first-class support in the upstream kernel that we may want to improve. Gregory noted that we may end up killing critical processes and that it may be unrecoverable. Gregory suggested that we cannot allow writes to go to the device uncontended although there would be performance implications of this. Gregory has an end-to-end configuration for this already in progress including separating the second tier into compressed and uncompressed memory to provide the necessary reliability while still having memory efficiency. The most obvious example was the lack of control over file writes. We will invite others from Google to attend the next instance of this meeting for more discussion. Gregory noted that he has a talk for LPC scheduled for compressed RAM that will cover his end-to-end design with performance numbers using qemu. We decided to dedicate the instance of this meeting in two weeks to this topic. ----->o----- Gregory updated on behalf of Joshua for the tier-aware memcg limits work. He noted that the LRU inversion issue was due to the system as a whole being pressured. They've concluded that there is no good solution -- when we are going to swap, wherever you can get the memory is probably the best we can do. Aggressive demotion typically just ends up resulting in much worse performance. For tier-aware memcg limits itself, there is a major versioning change happening for this. When testing previous iterations, there were issues when the amount of hot memory was larger than the top tier. They have a solid solution that provides fairness using memory.max, high, low, and min settings. The proportions that you get are based on the physical topology of memory tiers on the system itself (3:1 top tier to CXL provides 3:1 ratios for each memcg). The latest revision is going through production testing. Notably, there are no new tunables to configure. This is enabled through a kernel boot parameter, mostly for production testing. It also helps to avoid adding new userspace APIs while still iterating through solutions. Later, this could be enabled at runtime. Since we're in production testing right now, it's possible that this will move beyond RFC in the near term. ----->o----- Next meeting will be on Thursday, September 10 at 8:30am PDT (UTC-7), everybody is welcome: https://meet.google.com/jak-ytdx-hnm Topics for the next meeting: - Gregory's end-to-end compressed RAM design and performance numbers obtained with qemu experimentation - update on combined patch series for supporting non-temporal stores in migrate_pages() with memory error handling (series from Yiannis + Huan) - v9 of pghot and the PTE A bit based source (kscand) for inclusion in the upstream kernel - v6 of Shivank's series for enlightening migrate_pages() for hardware assists and his rmap batch series and LPC discussion - Teja's update on SDXI page migration based on AMD patches and hardware issues being encountered that do not result in page migration - update on tier-aware memcg limits status and production testing based on the latest major overhaul - 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!