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 53DE2D37E3D for ; Wed, 14 Jan 2026 14:59:23 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BFEFB6B0089; Wed, 14 Jan 2026 09:59:22 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id BB5FC6B0092; Wed, 14 Jan 2026 09:59:22 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A98206B0093; Wed, 14 Jan 2026 09:59:22 -0500 (EST) 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 979C16B0089 for ; Wed, 14 Jan 2026 09:59:22 -0500 (EST) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 657511A02EE for ; Wed, 14 Jan 2026 14:59:22 +0000 (UTC) X-FDA: 84330877764.20.D144325 Received: from smtpout.efficios.com (smtpout.efficios.com [158.69.130.18]) by imf21.hostedemail.com (Postfix) with ESMTP id D96E21C0008 for ; Wed, 14 Jan 2026 14:59:20 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=efficios.com header.s=smtpout1 header.b=EgpdmmB0; dmarc=pass (policy=none) header.from=efficios.com; spf=pass (imf21.hostedemail.com: domain of mathieu.desnoyers@efficios.com designates 158.69.130.18 as permitted sender) smtp.mailfrom=mathieu.desnoyers@efficios.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1768402760; a=rsa-sha256; cv=none; b=Eh+Obgok8eYo4T+Y7Dmc0xUvnX91Yrjcw8Qo+JFxyFkmXmkX676Wrf400WbhYqHrtSdf55 O0OTy95Dw1LhBr1z3epE7Q7Vmcayj+IB0qQ4v39PPX/TP4m4wMqlFKwXyWkGeDTOE3k5u6 Nda2vBkVXjkSlAAeyyJ7UrkiJ9ae3zM= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=efficios.com header.s=smtpout1 header.b=EgpdmmB0; dmarc=pass (policy=none) header.from=efficios.com; spf=pass (imf21.hostedemail.com: domain of mathieu.desnoyers@efficios.com designates 158.69.130.18 as permitted sender) smtp.mailfrom=mathieu.desnoyers@efficios.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1768402760; 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=gmDWQxZXl+iq5JtzXMv1UfK4Kj8WDaLba3HxCXNbTAQ=; b=no9yeaEfHoxvUom8vGGw87Xc50J3OxnuvXUwNP639wqs359p/WOFBMtUsbU3/qcp2mVEZ6 MHRAzEOnMFonLczJB6UIRfyLYyuBJFOrwQ4j/11/PYiq1t4eVTpNyulCP1Mx/E7dANQqoh TufIM+2JyI5fKZfmqvfLzWHwzCxvJlI= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=smtpout1; t=1768402760; bh=gmDWQxZXl+iq5JtzXMv1UfK4Kj8WDaLba3HxCXNbTAQ=; h=From:To:Cc:Subject:Date:From; b=EgpdmmB0iMS3s52XNQ4OgK/nv1/dt8wN4bABj6J/VpYqJeI+Lwqj6hh/z22KzuxbP D6VTr8rQAP07R2bVV3x7I8EvA50BSRZK9xTbbr6fZJ0J7gjOgIGDXUO88eKKlcYz1+ MbBLEcMlJGKQ/pCMgU+fY/bsJBXBDmla5XwPscX4mBRUZphWBCU4yCnbzrvRyuCrVq JsEvgMAbJM5OQYBYpIhaidMLaCaOpo9DDEnyH/TNZ78Y/DX45AUhiAVF2gCVXiF/Fh KaD6/13uRKUplAwxGTUm6/bKtq7d1jnydfPPube5mmOxltUe7YTZ6/GpBiR6H3lY1e qmCxRnV3dyRnw== Received: from thinkos.internal.efficios.com (mtl.efficios.com [216.120.195.104]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4drq5N0jGHzkxF; Wed, 14 Jan 2026 09:59:20 -0500 (EST) From: Mathieu Desnoyers To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Mathieu Desnoyers , "Paul E. McKenney" , Steven Rostedt , Masami Hiramatsu , Dennis Zhou , Tejun Heo , Christoph Lameter , Martin Liu , David Rientjes , christian.koenig@amd.com, Shakeel Butt , SeongJae Park , Michal Hocko , Johannes Weiner , Sweet Tea Dorminy , Lorenzo Stoakes , "Liam R . Howlett" , Mike Rapoport , Suren Baghdasaryan , Vlastimil Babka , Christian Brauner , Wei Yang , David Hildenbrand , Miaohe Lin , Al Viro , linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, Yu Zhao , Roman Gushchin , Mateusz Guzik , Matthew Wilcox , Baolin Wang , Aboorva Devarajan Subject: [PATCH v16 0/3] Improve proc RSS accuracy and OOM killer latency Date: Wed, 14 Jan 2026 09:59:12 -0500 Message-Id: <20260114145915.49926-1-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.39.5 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: D96E21C0008 X-Rspamd-Server: rspam06 X-Stat-Signature: 9uhqip17pqptkpdm55f36x3ond3bacjy X-Rspam-User: X-HE-Tag: 1768402760-333901 X-HE-Meta: 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 C1OzmFQl 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 d3/U9hmp 91fQpC3gLNs1hspk4gFxRCUJP9kg2y18zUXl8yXfURHeKWREuLGaIH6KTX0xjVqvuENCxiYiX2m3LGvO6HTClA== 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: This series use the hierarchical tree counter approximation (hpcc) to: * Increase accuracy of approximated RSS counters exposed through proc interfaces: With a test program hopping across CPUs doing frequent mmap/munmap operations, the upstream implementation approximation reaches a 1GB delta from the precise value after a few minutes, compared to a 80MB delta with the hierarchical counter. The hierarchical counter provides a guaranteed maximum approximation inaccuracy of 192MB on that hardware topology. * Implement the OOM killer task selection with a 2-pass algorithm. This is a latency reduction improvement of the OOM killer task selection: Testing the execution time of select_bad_process() with a single tail -f /dev/zero: AMD EPYC 9654 96-Core (2 sockets) Within a KVM, configured with 256 logical cpus. | precise sum | hpcc | ----------------------------------|-------------|----------| nr_processes=40 | 0.5 ms | 0.3 ms | nr_processes=10000 | 80.0 ms | 7.9 ms | I'm sending this series to gather feedback. I plan to re-submit it for inclusion into mm-new _after_ the next merge window closes, so the bug fix "mm: Fix OOM killer inaccuracy on large many-core systems" can be tested in the current release cycle. Andrew, if you have a prior version of this specific series in mm-new, please drop it for now. This series is based on v6.19-rc4, on top of the following three preparation series: https://lore.kernel.org/linux-mm/20251224173358.647691-1-mathieu.desnoyers@efficios.com/T/#t https://lore.kernel.org/linux-mm/20251224173810.648699-1-mathieu.desnoyers@efficios.com/T/#t https://lore.kernel.org/linux-mm/20260114143642.47333-1-mathieu.desnoyers@efficios.com/ Thanks, Mathieu Cc: Andrew Morton Cc: "Paul E. McKenney" Cc: Steven Rostedt Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Dennis Zhou Cc: Tejun Heo Cc: Christoph Lameter Cc: Martin Liu Cc: David Rientjes Cc: christian.koenig@amd.com Cc: Shakeel Butt Cc: SeongJae Park Cc: Michal Hocko Cc: Johannes Weiner Cc: Sweet Tea Dorminy Cc: Lorenzo Stoakes Cc: "Liam R . Howlett" Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Christian Brauner Cc: Wei Yang Cc: David Hildenbrand Cc: Miaohe Lin Cc: Al Viro Cc: linux-mm@kvack.org Cc: linux-trace-kernel@vger.kernel.org Cc: Yu Zhao Cc: Roman Gushchin Cc: Mateusz Guzik Cc: Matthew Wilcox Cc: Baolin Wang Cc: Aboorva Devarajan Mathieu Desnoyers (3): lib: Introduce hierarchical per-cpu counters mm: Improve RSS counter approximation accuracy for proc interfaces mm: Reduce latency of OOM killer task selection with 2-pass algorithm .../core-api/percpu-counter-tree.rst | 75 ++ fs/proc/base.c | 2 +- include/linux/mm.h | 49 +- include/linux/mm_types.h | 54 +- include/linux/oom.h | 11 +- include/linux/percpu_counter_tree.h | 367 ++++++++++ include/trace/events/kmem.h | 2 +- init/main.c | 2 + kernel/fork.c | 22 +- lib/Makefile | 1 + lib/percpu_counter_tree.c | 679 ++++++++++++++++++ mm/oom_kill.c | 84 ++- 12 files changed, 1295 insertions(+), 53 deletions(-) create mode 100644 Documentation/core-api/percpu-counter-tree.rst create mode 100644 include/linux/percpu_counter_tree.h create mode 100644 lib/percpu_counter_tree.c -- 2.39.5