From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-97.freemail.mail.aliyun.com (out30-97.freemail.mail.aliyun.com [115.124.30.97]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 627C337F318 for ; Sat, 17 Oct 2026 13:13:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.97 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792242844; cv=none; b=nr6dkNOtFmsHn9329ov705ut4YEDrsd6ZABCr8JAQ8NkGIRJYfvjZRBs6imgYlHSv5BhgSuc8GjB8LQUFAl2jiC65w1AeXTv8j6eN49A4LIolDABnf6oet9aNLSkKDbu1q2P8XnUX42x9cT/sWtEs+0I/K8rboY/Hf4JR/eugcE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792242844; c=relaxed/simple; bh=QjlSGpgxfiEShBSdnAIJv21OGrR3UYoK5MYiD0WDIqE=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=WPrRxY1dQ20mjn5BJcO7/aHsRW9M1tS1JlFN2ne8PH8wZm4mUVh1k8R9es0jqbyp4dy0FpwyjeK4TvlgcVRESMGm792RS0OwAwxUSr9PA6bFqO454J70Azc45f4C0B/McInCwpJOFIGHyyrQBc3L8QQCGYixdZazfI3d2a5GZRM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=S+IeRic3; arc=none smtp.client-ip=115.124.30.97 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="S+IeRic3" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1792242831; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=p1OMSvKiOynWMS149XzymCG5yePx5W1zvYizF/4+cRA=; b=S+IeRic388kEwWitan9ctAdR0a0xp628fp6mQWadXIoA5GfdeCGzgZsWaFOocAKI+m3tZDRIfMvvEB+A2fDgi+oiuoYKGB7ppRKLpgsL4lkO/LnECtPkbkSnHMsZK5H0yYReE5Y8OkWRh3iltzleHy4fatAkjI/CqxYoMhEJnnQ= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R181e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033045098064;MF=peng_wang@linux.alibaba.com;NM=1;PH=DS;RN=20;SR=0;TI=SMTPD_---0XCxEdgs_1792242830; Received: from localhost(mailfrom:peng_wang@linux.alibaba.com fp:SMTPD_---0XCxEdgs_1792242830 cluster:ay36) by smtp.aliyun-inc.com; Sat, 17 Oct 2026 21:13:50 +0800 From: Peng Wang To: Anna-Maria Behnsen , Frederic Weisbecker , Ingo Molnar , Thomas Gleixner Cc: Peng Wang , Greg Kroah-Hartman , "Rafael J . Wysocki" , Danilo Krummrich , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Peter Zijlstra , Waiman Long , Tejun Heo , He Rongguang , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, driver-core@lists.linux.dev, linux-trace-kernel@vger.kernel.org, cgroups@vger.kernel.org Subject: [RFC PATCH v2 0/2] tick/nohz: Add per-CPU control of non-idle tick suppression Date: Sat, 17 Oct 2026 21:13:40 +0800 Message-ID: X-Mailer: git-send-email 2.47.0 Precedence: bulk X-Mailing-List: driver-core@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit This series adds per-CPU control of non-idle tick suppression within the boot-time nohz_full set. The policy can be changed without taking CPUs offline. Some cloud hosts pin vCPU threads one-to-one to host CPUs. At full allocation, housekeeping CPUs also provide vCPU capacity and always retain their non-idle tick. Operators want comparable performance for otherwise equivalent vCPUs, regardless of CPU placement. Retaining the non-idle tick on nohz_full CPUs as well avoids one placement-dependent difference in host tick interference. With spare capacity, selected nohz_full CPUs may stop the tick to reduce host scheduler-tick interference with vCPUs. Allocation changes as VMs are created or destroyed while other VMs remain running. A vCPU thread may be the only runnable task in either state, so existing tick dependencies do not express this policy. The per-CPU nohz_tick_allowed boolean defaults to 1 (allowed). Writing 0 prevents non-idle tick suppression; writing 1 allows it, subject to existing dependencies. Readback reports permission, not tick state. This leaves idle tick suppression, nohz_full membership, context tracking, RCU offloading and housekeeping configuration unchanged. This series depends on the separately submitted nohz kick fix [2]. Testing used that fix together with this series in x86_64 KVM guests, with NO_HZ_FULL enabled and disabled. Changes since v1: - Following Greg's sysfs feedback [1], replace the global CPU list with a per-CPU boolean, removing the list-size and custom parsing issues. - Rename nohz_full_allowed to nohz_tick_allowed, as suggested by Waiman. - Explain the vCPU allocation use case and clarify permission semantics. v1: https://lore.kernel.org/all/cover.1792067271.git.peng_wang@linux.alibaba.com/ [1] https://lore.kernel.org/all/2026101743-monotype-demeaning-f97b@gregkh/ [2] "tick/nohz: Requeue kicks flushed outside hardirq context" Message-ID: <43668cf88d976084e2865ec07dea82b64ad402ba.1792240863.git.peng_wang@linux.alibaba.com> Peng Wang (2): tick/nohz: Add a policy dependency for full dynticks cpu: Add per-CPU control of non-idle tick suppression .../ABI/testing/sysfs-devices-system-cpu | 27 ++++++++++ drivers/base/cpu.c | 53 +++++++++++++++++++ include/linux/tick.h | 8 ++- include/trace/events/timer.h | 3 +- kernel/time/tick-sched.c | 42 +++++++++++++++ 5 files changed, 130 insertions(+), 3 deletions(-) base-commit: 70dd4ee72eb2d5793c62e71c14e3aba78e5a4e56 prerequisite-patch-id: 6036ece815f0ab92a0413d433675d5b240b7a8c1 -- 2.47.0