From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8001A606A326 for ; Tue, 3 Nov 2026 01:30:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=R3cSXNEU Received: by kanga.kvack.org (Postfix) id 93C986B05B5; Mon, 2 Nov 2026 20:30:03 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8EC2D6B05B6; Mon, 2 Nov 2026 20:30:03 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 82A1B6B05B7; Mon, 2 Nov 2026 20:30:03 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 5E81A6B05B5 for ; Mon, 2 Nov 2026 20:30:03 -0500 (EST) Received: from smtpin02.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id EAEA1C02F0 for ; Tue, 3 Nov 2026 01:30:02 +0000 (UTC) X-FDA: 85392076644.02.22B2A13 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf13.hostedemail.com (Postfix) with ESMTP id 594F920002 for ; Tue, 3 Nov 2026 01:30:01 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=R3cSXNEU; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf13.hostedemail.com: domain of sj@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=sj@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793669401; 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=JL0qvT8ZjJjiuievn8oHTO+mTi5spxR1dpR3Ut9PSkc=; b=xiXUWt7YZWvxPY6j6GPPlgOvx8Ovk/2X4qTthH9O1j8SgG5cA22CUCWdmUZnkR8i5e0Fm8 7nh7dPhF9mPrOYUW15z3wkqQH9Wty7kUjohi5Wt5NxrZZztsQFy7Q7D5K9oHXxoZHT2Z8J 7oCz2JYrP7VRN0kPevv+kjCX3kBsiJE= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=R3cSXNEU; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf13.hostedemail.com: domain of sj@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=sj@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793669401; b=YlhQWy8G420Jgu3C9nv1kQHni5+ueLFoIdKkeKw6jRDLnhFt8zFz5GNMrrcZ69qBi0kK6H +CpcvivMg4+G2s4tHexTtAw1VVJH512f+bKcbni+VB+16wD0BJTFLWsQWw/D7wrP3BKBlJ xcZVgaxRCHviNp/UUEAO9kFGISomr40= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id CC16040806; Tue, 3 Nov 2026 01:29:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 33B781F000C1; Tue, 3 Nov 2026 01:29:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793669399; bh=JL0qvT8ZjJjiuievn8oHTO+mTi5spxR1dpR3Ut9PSkc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=R3cSXNEUgnb3K9YOWjnMQqFH+EiogBKNMMLkot4qCORp6kHRUaaVhX1jCsg7RTM0d F9nMpF9n9e76JMZcvCUeVOLI1GJJYz20/HE6P+rlUcTLBX9dz163Lz2Cr4WWcTBFJx SSc32ghlzCrYzhzdgN2qRpBfo0/MkVgKbE732CGSlcPVMc9HMy9RQqMNWD0PtwQ9tA +iz9py1Vw+1YdOefU9z+3YfR/JzCkfrw1PYU/yQLxxUSSO2E9lqbEkjVphHn3/lHcO Tn89iFq3+Isg31Pvh4tCnu2qmOz7o0YHdBHoINyTS9bCr4Z0PJak+1q/8AdYOZWwom Rs1wUnMZKdvEQ== From: SJ Park To: Joanne Koong Cc: SJ Park , akpm@linux-foundation.org, yosry@kernel.org, shakeel.butt@linux.dev, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, muchun.song@linux.dev, nphamcs@gmail.com, chengming.zhou@linux.dev, david@kernel.org, ljs@kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, damon@lists.linux.dev Subject: Re: [PATCH v1 3/3] mm/damon/core: use node counters instead of flushing the root memcg Date: Mon, 2 Nov 2026 17:29:51 -0800 Message-ID: <20261103012952.93674-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261102225030.2743129-4-joannelkoong@gmail.com> References: X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 594F920002 X-Stat-Signature: g81ubiqjhm8oqqzrzqguhjo7raj8qhah X-Rspam-User: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793669401-711392 X-HE-Meta: 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 Z7M4s0N9 ymhlJwEwlsObzL+uzJ+BFX6mR/6YUTi2X5Xqjs8pioO4kMYseytJ+fFYHl4OixD9egiMFZWqG8ybGAcAoxE7ocdYMa0LxYafgTB2L26QXG0dBbYqEecCVYFnRi/yoJunZjX27h0aSPHhCY52SV/wFQyWln9/XJZzQyHQjJPhNn+4uFWAUYGE3O96oufPAwnr+JA0tt0+MzQbJ/jXLw4hfJei1AzBjCQYJszcpxwFN/w5vSRwpn67Y6zF9PvZWjsHI/mnV2MQEZDqgNvuLWmPthUm3yA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Hi Joanne, On Mon, 2 Nov 2026 14:50:30 -0800 Joanne Koong wrote: > damos_get_node_memcg_used_bp() flushes the memcg stats before reading > the LRU sizes of the goal's memcg on the goal's node. For the root > memcg, that flushes every cgroup in the system. The flush is not > ratelimited, which means it happens every time the goal is evaluated. Just thinking loudly. damos_get_node_memcg_used_bp() is called only once per DAMOS quota reset interval. It is usually recommended to set the interval to 1 second. So a sort of rate limiting is applied in common use cases. That said, some users might using quite short interval. And it is obviously better to avoid unnecessary flushes. > > For the root memcg, the node counters hold the same LRU sizes as the > memcg rstat stats, and they are always up to date. Use > lruvec_lru_page_state(), which reads the node counters for the root > memcg, and skip the flush for the root memcg. Again, loud thought. For root memcg, users might use DAMOS_QUOTA_NODE_MEM_{USED,FREE}_BP instead, which calls damos_get_node_mem_bp(). That said, some users might use DAMOS_QUOTA_NODE_MEMCG_{USED,FREE}_BP for root memcg (maybe it makes user space tool writing easier?). So, looks all good to me, thank you for this patch. > > Signed-off-by: Joanne Koong Assuming the discussion on patch 2 concludes to have lruvec_lru_page_state(), Reviewed-by: SJ Park Thanks, SJ [...]