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 1C740E8B38B for ; Wed, 4 Feb 2026 02:25:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5D1146B0005; Tue, 3 Feb 2026 21:25:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 57E916B0088; Tue, 3 Feb 2026 21:25:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 47D8B6B0089; Tue, 3 Feb 2026 21:25:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 32C7D6B0005 for ; Tue, 3 Feb 2026 21:25:50 -0500 (EST) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id C9E7C140645 for ; 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imf07.hostedemail.com; dkim=none; spf=pass (imf07.hostedemail.com: domain of yunjeong.mun@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=yunjeong.mun@sk.com; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1770171948; a=rsa-sha256; cv=none; b=lmqwyyl8k749X+ejUAPDJVHoBei56iGk5AnluTxZM3Cc9Cz/08fDnW3zJx7ibuTYm0zJC+ WedMwfPgj+RdRGcTNtRBw5xavZnvu76rKpXHiPBnWxRzS+FMZtfsw4x4g3wnLrXdzMO+HD TFRephs3gmaR4NCUOSnVdAI0xp42Eho= X-AuditID: a67dfc5b-c45ff70000001609-89-6982ae246dfa From: Yunjeong Mun To: sj@kernel.org Cc: honggyu.kim@sk.com, kernel_team@skhynix.com, Ravi Jonnalagadda , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, akpm@linux-foundation.org, corbet@lwn.net, bijan311@gmail.com, ajayjoshi@micron.com Subject: Re: [RFC PATCH 0/5] mm/damon: Add node_sys_bp quota goal metric for Date: Wed, 4 Feb 2026 11:25:35 +0900 Message-ID: <20260204022537.814-1-yunjeong.mun@sk.com> X-Mailer: git-send-email 2.48.1.windows.1 In-Reply-To: <20260124015045.78075-1-sj@kernel.org> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrLLMWRmVeSWpSXmKPExsXC9ZZnoa7KuqZMgz+7RCxW7G1lt5izfg2b RcOPz2wWTw60M1o8+f+b1WJh2xIWi8u75rBZ3Fvzn9Xi5FsHi8Nf3zA5cHnsnHWX3WPTqk42 j02fJrF7nJjxm8XjxeaZjB6L+yazenxf38Hm8XmTXABHFJdNSmpOZllqkb5dAlfGqyOnGQuO CFVMODCdpYHxPV8XIweHhICJxJpTfl2MnGDmxDXP2UBsNgENiYOHTjKD2CICghL9j2ewdjFy cTALrGSSuLj4CRNIQljAR+L6udVgNouAqsTrjTfYQWxeATOJ+ZOPMkMM1ZRouHQPrIZTwFhi 2t9NrCC2kACPxKsN+xkh6gUlTs58wgJiMwvISzRvnc0MskxC4DKbxMvzr1ghBklKHFxxg2UC I/8sJD2zkPQsYGRaxSiUmVeWm5iZY6KXUZmXWaGXnJ+7iREY6Mtq/0TvYPx0IfgQowAHoxIP b8DHxkwh1sSy4srcQ4wSHMxKIrzp0+szhXhTEiurUovy44tKc1KLDzFKc7AoifMafStPERJI TyxJzU5NLUgtgskycXBKNTDaSbhoL+LZedW48e7tpSK/NZdECp/hM7y1NkPEX1VVKJ+N9dkm tXO8nuJV4d+vzvhrkyP2Ts/+lZrLBKlXJordIReXr53i5uH3xTm+LWgvo84xz+kfpAr3zONz NVOY9ONumYj2kr8+lhaPi1oW68/ZLpvJp+bqq9d3dMXLzUXqtlEprw34lJVYijMSDbWYi4oT AVNY2FBwAgAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrHLMWRmVeSWpSXmKPExsXCNUNWR1dlXVOmweE/rBYr9rayW8xZv4bN ouHHZzaLJwfaGS2e/P/NavH52Wtmi8NzT7JaLGxbwmJxedccNot7a/6zWpx862Bx+OsbJgce j52z7rJ7bFrVyeax6dMkdo8TM36zeLzYPJPRY3HfZFaP7+s72Dy+3fbwWPziA5PH501yAVxR XDYpqTmZZalF+nYJXBmvjpxmLDgiVDHhwHSWBsb3fF2MnBwSAiYSE9c8ZwOx2QQ0JA4eOskM YosICEr0P57B2sXIxcEssJJJ4uLiJ0wgCWEBH4nr51aD2SwCqhKvN95gB7F5Bcwk5k8+ygwx VFOi4dI9sBpOAWOJaX83sYLYQgI8Eq827GeEqBeUODnzCQuIzSwgL9G8dTbzBEaeWUhSs5Ck FjAyrWIUycwry03MzDHVK87OqMzLrNBLzs/dxAgM5WW1fybuYPxy2f0QowAHoxIPb8DHxkwh 1sSy4srcQ4wSHMxKIrzp0+szhXhTEiurUovy44tKc1KLDzFKc7AoifN6hacmCAmkJ5akZqem FqQWwWSZODilGhhvufOnTTnH8ndiosISu2RJz/YLzHeuKtyV0Ix8npbhcUrvr57a3X7+5uUG QQV91sdqmVZOXSKrH9S3/G+216PHhVMjw65Ed0o9YjJuYTgkkHX25bJPNo36FTy7vnVe+WiT aOis1iS80ab6nFccq9jPqdcXete0uMblP9e5kbTwXWzyLcnXN5RYijMSDbWYi4oTAfwAvkph AgAA X-CFilter-Loop: Reflected X-Stat-Signature: fjwanzmpq78sg86s7kd94ehwbz8mq6ax X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 37B334000A X-HE-Tag: 1770171945-486787 X-HE-Meta: U2FsdGVkX1+/skKYXvqmtViIaHs0i3LOiQnylShEFXc+U05UaN/o+/gNsFfcRu2PoFb9GxqG33YfWeZRZt1LrnZB+j/t2iIyultY37MQ8o0K+KuzxqtYFnInO+DpOVryI8NNxCrnHhiDK+ZJ28AVActMaeKQDlwebNcdV0hnuNkFVh/py1GQ4TTT7beFBLjmHuFsqU3cezP8nAW7IGuf4dumfJYuuSDQFuxzsaAlJAN/2f+VUHXHegV3vkminIEnVI83ihttGSfMDHVxAYM5fbxnGL/TLwl3JqLEhwKZZ1Kdkk5wrt/n0rWxvmpXI6OkHDbXxS4Q1MYh6OHgRPim1EtYSJ0rgHi16l3V4sCDGsdIb4s8e0/badySOH7FwsF4O+x0nMOJ8uP67sdraGdtlWpGoq6vZSyxJNsZceHJB5bEprRWybjnpjpZB394p+8HGJxLbU3t3Ok34RKj9EAnD33PlCx6mGNsJQ56wyp8VaeCV0DFTZyr3TSOhGCW5hYGIXXWVJy1bQdrhq4FgRJaKTvvj3OD7M9sr6YOXcGrK8tIcswxycpYlUP0aCGTQJWdbOxPQ4vwKNvLDaDb6xJ4Sowxoucny7wal2p5ssUKyDMUU1REIqTdMYhwDehXsAFdvQTrEg6mxMo05H4l3iE0RcFc36V3rMqSPUCXv+6h6Ri86xeHadMjrwoBculGq67s1Soj2VLwsFOTRufOIpMv5janpwRJQa7jdYInllmutv+meT9bB0REPmBe7jYdtWJ5NB59DSVXMtuePdsgG/e12z2wkLb4/QdXSsCWXhlfF3apPEc3hW+0APd160WG7I5FG4TScw2k+3E4Tpn6eKcd1pKRTP1QEhMr47Q5hMXaFTapoW6ZkXLBrDzSgyf0q2lZ8FtmdI3qpVkfoQTd4ln1WWRrzKOUaufMoxlxKCj6XHy36BNXNZNv3A9CTJ9AZ5rLBi/1kpTmUT5sn5+QYjA dw2uRitJ EKvPCRR1vRG3QDiD/czCXdV//AgOCRSvEv+MJwYiGywa6sFRY170qKMXWeprQA0pK8lJm 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: On Fri, Jan 23, 2026 at 05:50:43PM -0800, SeongJae Park wrote: > Cc-ing SK hynix folks (Honggyu and Yunjeong) for quota auto-tuning behavior > confusion (not stop immediately after satisfying the goal) I discuss below. > Hi Seonjae, thanks for Cc-ing us :) > > Please note that the goal-based quota auto-tuning works in proportional way, > preferring small steps and "eventual" goal convergence. As a result, migration > will occur a few more times until it is completely stopped after the goal is > satisfied. Unless there is another scheme that migrates pages into node 0, you > may end up having node 0 having a bit less than the 40% memory. > > > > > No oscillation - migration stops when target state is reached. > > So, little bit of oscillation could still happen. Hopefully that shouldn't be > significant, though. > > IIRC, SK hynix people also confused with the behavior when they experimented > migrate_{hot,cold} action with NODE_MEM_USED_BP goal based quota auto-tuning, > but using only a single scheme that does migration in a single direction. > Because this is at least second time it made confusion, if you need, maybe I > can try to add a feature for making DAMOS immediately stops after the goal is > satisfied. Let me know if such new feature can be useful for you. Cc-ing SK > hynix people (Honggyu and Yunjeong) so that they can correct me if my memory is > broken, or answer if the new feature I described here can be useful for them. > Yes, you're absolutely right. Currently, esz(effective size) starts from 0 and esz gradually increases as `current` approaches `target`. Once `current` reaches `target`, `esz` then begins to decrease. However, we observed that even after `current` hits `target`, migration still continues relatively aggressively - because `esz` remains high, and it takes time for it to decrease. To address this, we previously suggested that initializing `esz` at `target` (or something suitably large value, rather than 0) and letting it gradually decrease as `current` gets closer to `target`. This would allow for stronger migration when `current` is far form `target`, and gradually weaken migration as `current` approaches `target`. Such a feature would be useful for us to experiment with tiered memory system :) Best Regards, Yunjeong