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 C5330C43602 for ; Mon, 29 Jun 2026 13:00:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AC0D96B00B4; Mon, 29 Jun 2026 09:00:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A71B86B00B5; Mon, 29 Jun 2026 09:00:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9870F6B00B6; Mon, 29 Jun 2026 09:00:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 76A976B00B4 for ; Mon, 29 Jun 2026 09:00:54 -0400 (EDT) Received: from smtpin10.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 02DDE1A06C1 for ; Mon, 29 Jun 2026 13:00:53 +0000 (UTC) X-FDA: 84932960028.10.D668EA2 Received: from out-178.mta1.migadu.com (out-178.mta1.migadu.com [95.215.58.178]) by imf23.hostedemail.com (Postfix) with ESMTP id 0F80C14001A for ; Mon, 29 Jun 2026 13:00:51 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=PhYScBkp; spf=pass (imf23.hostedemail.com: domain of usama.arif@linux.dev designates 95.215.58.178 as permitted sender) smtp.mailfrom=usama.arif@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1782738052; b=j5HPW+NI7IzASHo89Ez9l51rM8qBfvA+uuIATcmFcYK4f8s2gK7XHLK7MRM7nkgDdB5LQV LMdQ4tHywcpXO5UPd0BLMad1QCdLR7KJ3DRT6rfPB52PX8BJ+6djUqG5Y/HNZKX7R+ilm9 1+mPSX2yWm9XOwRcwElJR/gooKUeWxs= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1782738052; 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:references:dkim-signature; bh=bymgERp/YFbwVBxVzPFXfDs+LSnZmVynKzWNDPQQDUs=; b=b0OmoFPtigi1XfHnokIVWUo/DJIpzqtoTkrLtaoKWVsCD/gZXZP7yhW30UKCkDaFXVKjA/ E44eyxOFXUtfggvWPp3FFOb8R5OxxoQOrbCPBMRERDyhrEo31BJA2d5A8+m2W1wwokg+bR VpmR16Z/ycD4q2GPFuw06+IDtDPhdyk= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=PhYScBkp; spf=pass (imf23.hostedemail.com: domain of usama.arif@linux.dev designates 95.215.58.178 as permitted sender) smtp.mailfrom=usama.arif@linux.dev; dmarc=pass (policy=none) header.from=linux.dev X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1782738049; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=bymgERp/YFbwVBxVzPFXfDs+LSnZmVynKzWNDPQQDUs=; b=PhYScBkpS+3gjZ3UnAmke9dWXpY17VSXA8SzjnJZh3XYFBt2diml52/3bsONtdCJX2Z3IO gGFZlyWXt6jw1gfKOoHN1F+lePE0FNBVsUL3yYK09EOb79m2QBYFJeK4/CszI3SK3zkBMt doM3b2Kc7q5rztN4Sa2S4Rz8mTfCz4c= From: Usama Arif To: Andrew Morton , david@kernel.org, linux-mm@kvack.org Cc: hannes@cmpxchg.org, tj@kernel.org, mkoutny@suse.com, shakeel.butt@linux.dev, roman.gushchin@linux.dev, liam@infradead.org, linux-kernel@vger.kernel.org, ljs@kernel.org, mhocko@suse.com, rppt@kernel.org, surenb@google.com, vbabka@kernel.org, kernel-team@meta.com, Usama Arif Subject: [PATCH v2 0/2] mm/vmpressure: reduce CPU, memory and code overhead on cgroup v2 Date: Mon, 29 Jun 2026 05:59:35 -0700 Message-ID: <20260629130042.2649505-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 6s9gooqz494gxuo3f5iz99syxzwhf136 X-Rspamd-Queue-Id: 0F80C14001A X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1782738051-821214 X-HE-Meta: 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 ir+8oxRr CvbZUDFIDKOOPA+CbDSTWg8XdyoiWemau1qRFj+c+mVvXR3MXW9PKcY/4AmfDI9Z7hwFJ/GUpgb7KeAtIqQGhABwCK6p2ZYiRXv+JrQY10Z72Ys0rqnFYN1pcb57wbxw7BHuBiTecHtvid8UU7pwx7IpB+LMTsd7w8VzCjcLaDk0XFQOUxefI3bYZGX2ngQi56YFmee9vUzS3yyYTJpt4ScXqmLr6se/6luhg Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The vmpressure subsystem has two distinct consumers, gated by the @tree argument: tree=false : in-kernel socket pressure, consumed by TCP/SCTP. This is cgroup v2 only; v1 sockets read memcg->tcpmem_pressure instead. tree=true : cgroup v1 userspace eventfd notifications via the memory.pressure_level / cgroup.event_control interface. v2 has no equivalent (userspace gets reclaim signals through memory.pressure / PSI, which doesn't touch vmpressure). So of the four (hierarchy, tree) combinations, only two carry data that anyone reads. The existing early return in vmpressure() covered v1 + tree=false; the symmetric v2 + tree=true case was falling through and doing the full lock / accumulate / schedule_work / parent-walk dance, even though the events list it eventually iterates is empty on cgroup v2 (vmpressure_register_event() is wired up only through the v1 cftype "memory.pressure_level" and can't be reached from a v2 memcg). Patch 1 extends the existing early return to also skip v2 + tree=true. On a v2-only host this eliminates a contended path where reclaimers can serialize on a single global sr_lock. bpftrace on a 176-core production host (cgroup v2, 285 memcgs, sustained reclaim) showed ~16,200 such calls per minute with tree = true. Patch 2 follows up with a cleanup: it splits the v1 userspace eventfd interface (struct vmpressure_event, the events list and its mutex, the work_struct and its handler, the parent walk, vmpressure_register_event / unregister_event, and vmpressure_prio) into a new mm/vmpressure-v1.c built only when CONFIG_MEMCG_V1=y, behind small no-op stubs in the header. mm/vmpressure.c keeps the shared bits and the tree=false socket-pressure path. The size of vmpressure.c goes down to half and the code is much more simpler. The only #ifdef CONFIG_MEMCG_V1 remaining in source is around the v1-only fields inside struct vmpressure itself. Memory savings on CONFIG_MEMCG_V1=n: struct vmpressure : 112B -> 24B struct mem_cgroup : 1664B -> 1536B This split is the first step toward eventually making vmpressure CONFIG_MEMCG_V1 only. The v2 in-kernel socket pressure path (tree=false) cannot be removed today immediately: PSI is not an exact replacement for vmpressure, and switching networking socket-buffer back-off to PSI may regress networking performance or increase memory pressure in workloads that today rely on vmpressure's hysteresis. The medium-term plan is to introduce a PSI-based socket-pressure path, keep vmpressure available for v2 behind a defconfig as an opt-out for several releases, and only then drop the tree=false path entirely, at which point everything that remains in mm/vmpressure-v1.c is the whole subsystem. --- v1 -> v2: https://lore.kernel.org/all/20260606114158.3126210-1-usama.arif@linux.dev/ - Add more in commit message about future plans of vmpressure for cgroup v2 (Shakeel) - Remove unnecessary return statement in vmpressure for v1 only tree path (Michal) - Rebased onto latest mm-new Usama Arif (2): mm/vmpressure: skip tree=true accounting on cgroup v2 mm/vmpressure: split v1 userspace eventfd code into vmpressure-v1.c include/linux/vmpressure.h | 46 +++++- mm/Makefile | 2 +- mm/vmpressure-v1.c | 305 +++++++++++++++++++++++++++++++++++++ mm/vmpressure.c | 302 ++---------------------------------- 4 files changed, 363 insertions(+), 292 deletions(-) create mode 100644 mm/vmpressure-v1.c -- 2.53.0-Meta