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 9C298E7FDCF for ; Wed, 4 Feb 2026 06:06:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id ABADD6B0005; Wed, 4 Feb 2026 01:06:52 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A67D96B0089; Wed, 4 Feb 2026 01:06:52 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9917E6B008A; Wed, 4 Feb 2026 01:06:52 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 87F066B0005 for ; Wed, 4 Feb 2026 01:06:52 -0500 (EST) Received: from smtpin15.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 2B17F1A06DC for ; Wed, 4 Feb 2026 06:06:52 +0000 (UTC) X-FDA: 84405740664.15.E38E516 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf04.hostedemail.com (Postfix) with ESMTP id 71D8240013 for ; Wed, 4 Feb 2026 06:06:50 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=k6pDqTIf; spf=pass (imf04.hostedemail.com: domain of sj@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=sj@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1770185210; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=NFDVggU2Y4zYIw5mPBf6KrhqPL/xBMVfQOvvo1nS1VY=; b=nb02fdLvW+4sXlCKCluILF0Ddeaf1zxGOS4A+P7TK7vSY3Gy13Ltj0Ini4h2CHxT2rjgci y6RlDxsC7SJ9uKVMhWEQtGgrWuQoz94MYtAAR96G5hXSwEUl/yUrNKF7EAGXve80qunfWM /yExgXr4KnfYco1QXiX35Hauy4l2dME= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=k6pDqTIf; spf=pass (imf04.hostedemail.com: domain of sj@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=sj@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1770185210; a=rsa-sha256; cv=none; b=qMguHNmzas11bY/cxvXiBLSCBof5eVf5hBbQUiNdtOEx1IR3ZULTJFYxRhZOGhIu4p7fzq Kx/avh7ZDWT6gNe1m3qCTB4KM6M5XxH0tBmY8FpqljYPdcqH18g4qxLUzoHdkFWfWzQBO/ nF+yjKhLNJJWthfQIizmGjRVg8soENU= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 398C14088C; Wed, 4 Feb 2026 06:06:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C9261C4CEF7; Wed, 4 Feb 2026 06:06:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770185209; bh=YDx6StxtpDi58Lvtwkex+sore9y1zO7/lL+DfNC6Sq8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=k6pDqTIfKYSOHU297/fPjNP2NvQ2xMkHZOQq1eSZ1tF7slzQRnBqZSAx9mYGWMNTI aDngLHWLLoiXoqHGUhdRuHyDbRuNrJgxWYqT8TAU4x5KHzX9lYalnmB66IJxPn4QWH K14oTzSPh9cCeq9Yl4j9WgXaUD4G3zC5q0gwicfMNIjWmuW8v9rpHGL0XKeqD+9c9W 0HJv99ge8aOev5BnLoYfuzMuj4Z7G5idL05MuBDsByOXgguTSzazN8od7p6lg6+fcQ QVxH6vkHAu+0zW+TsFySilcaTUZMRmRqtf0JyXDeJg/jLhPFAEheKsbVC7RNbdjv+0 vJp1A34Yv4nxg== From: SeongJae Park To: Yunjeong Mun Cc: SeongJae Park , 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: Tue, 3 Feb 2026 22:06:40 -0800 Message-ID: <20260204060641.97191-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260204022537.814-1-yunjeong.mun@sk.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: putsbudtrs1efn6mpdgqkpzd1drqnk4w X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 71D8240013 X-HE-Tag: 1770185210-156881 X-HE-Meta: U2FsdGVkX18Llnm8vyacZbNnWRg7aJxFKRFG67pn7Zl/k6v/3Xcg+23vFNwHd2ccUy22GPsNn3Kk2pbIJ3iEZYMfkMaB8A4cAB5A07VWmoTDsVxb9ZfzBqSN8MtFVM7GiZcs0vVWJF5aeNeHYhHJp4fBTggHjGpuVdOLE3vRUmj8ppTbwx0Ew3rWtPhdWt0YEI7OjxnH9MNNQg0IWtd1J49+ZNkjK+NjHENGC0mBlIIWXALkII98yk65JgluBIBcBdDiiqC/mS0JyOTErfYFbyNgCjDYZ4xCv8IGWFT/uP0U7X/hjsbaD1zSxFivTF6Vp1AGXv6ItNV/YgobHfCiuq01y6YPn4DB0Fo7nkQ6V5C/UFUVtUVqI0OvD90NBDm7Z7OfBsg197ol7FixKzme3I+NnaQGYCEn9//FWnZbaanV4vvyFc6MkNps9HORw6UvhbfZ3EVAv0PdUehHUtAC/8CxV0R0ZxXJkkQW6qpmQHUfahn1qumQ94DnL2w2xRqivn97NGc90/yfg/gMu9Egcy/fWqGhldXwO3J2J7gEZ5u8u+4DhADrKjsctEjBn0IkzisOOn/WBxvbIbOrVLCTBUKjJuvGiOp+XMhJtAFua53qdaqqyVaX3y0Sm/8xLkwQIvp//o7vM1TiYg0Ap61ff1oldchGCilxuOh2h1jOEcF+TcuVWO44Z0D1detdGe8p47o0/gSpkQe9po0C04CVrryX8GUJybgTjItrvNdfWRmif8Jpu/qVh0LKkUh3VofaD8vpNq0RHKhXs93mD57PSYA/Cw5AN+zVZGSZgQbzQ3SLibC06flPPqDg4ZtjsV5yuoqEKS9o7rFGwozGEdm/04s8s17VPF8xFu23N6EjgsUtg5WNovW2npyFZgU8qHK8fIFx+2uYsBrogqrt4lo9sYFYGaqfUCV0RnyFj6WvAwUufukyEdHK9DxHiRrbA5mgqJrD+Z+PFkhWTLSr+ux CxM+ADoh +9aUylT3hwkJrFPURbwbSYz13G6x67ycnPrjz4VbCzyZ+AFz0rSfprvKmK4caRb5g1mk5EkAX+glZr21ODfcs6Y68gb44BkHqkBvJBK1NFwsMz0m10oZy37ocNrDsMws1R8ljdzSY5DY0ZrZDvTUebxlkSdhgZf8XOoi4Vbz7KuA6DfHcIC09mJ0vZ63SKO2O0uAn2mmhEmKgKAXKQ1SYiNCEFBvaPlHuKmygg3jhNqdfAcrQJxu9+xyNia5qI4XvkRfrlTqo5hnvJVRFGB9JjKZwJVNA1hbeSv6fBRkbSJ3tqg8t38PYdU/JcjcVgeMnMXF4Pmc1V2N8vh5lGykapogwMbDZnSXi8mcdgdE3qeISFrwU3JmWW7OTPbxYBtqPH2bp X-Bogosity: Ham, tests=bogofilter, spamicity=0.000016, 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 Wed, 4 Feb 2026 11:25:35 +0900 Yunjeong Mun wrote: > 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 :) Thank you for confirming, Yunjeong. I now agree this is what really need to be implemented. And I agree your suggestion makes sense for the use case. I want to take sufficient time for good design of it, though. I will share update as soon as I get some idea. Thanks, SJ [...]