From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 3B7D53009E2 for ; Thu, 25 Jun 2026 05:28:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782365285; cv=none; b=qEhHxpKiVusZg4Y6fqEMy01lj2RiAJIsJ+M4xwXY990IFRD09GAJqvnutlerRh6LLO5HQSEgdcH8MjvGjgKM7DMwKkXVtjZ6Xx9jbimHErzK6diWuyMShJ09lv/6fiYc1O8AU8Ut75i63npqFvgITBOLV3mqCJh5n57INSKxrg8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782365285; c=relaxed/simple; bh=aTi/pXkw91hda8Kdn4Vpsi0Sl3Y5Vo7qzyAsuTxvfuI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=cwql9JxlDx/09u4We+bzsor/PG8KMdaWI2ejqdYY+cqcn2MGyHclMq7rLTIROMxMFaoc3/Rrdv2mj2kn8eYrpxM5/6ZHq/Vt6jx2ZHi3hNOf0DfwVfALe7c8NYHRTD0C1HW6aTA86qEc7eFMdLNhIFSp+b7n5qEXj1/b8lZ61R0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=XhtSAMZ0; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="XhtSAMZ0" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1782365283; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tkCv2oYuzPEka7BacCiWxFFuaGiHcvr95rXSLBOAyWM=; b=XhtSAMZ0cBOGE9qM5taYZ6Qfa3unMbY/S+EBi+m8Jl3C8RyX9z1dHd4WbID8iEZUXvHJG8 cBHcNdijU1PT1fxfAhq6ySKU6NGY1H8PD7e7z7XTVzkwUZ9gKgcIczWvA3taSwZt/MSrMS ttmPnhrry1Lp3w3m/7WZe5xniZ5uCSw= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-465-i-fo0p_PO5-DT5CegNM5ZQ-1; Thu, 25 Jun 2026 01:27:59 -0400 X-MC-Unique: i-fo0p_PO5-DT5CegNM5ZQ-1 X-Mimecast-MFC-AGG-ID: i-fo0p_PO5-DT5CegNM5ZQ_1782365278 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7DDAE1956043; Thu, 25 Jun 2026 05:27:57 +0000 (UTC) Received: from [10.2.16.163] (unknown [10.2.16.163]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 7B4121800677; Thu, 25 Jun 2026 05:27:55 +0000 (UTC) Message-ID: <4ad24488-9cc1-4f1c-8dc5-6830ae7420df@redhat.com> Date: Thu, 25 Jun 2026 01:27:54 -0400 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH-next 00/23] cgroup/cpuset: Enable runtime update of nohz_full and managed_irq CPUs To: Jing Wu Cc: Thomas Gleixner , linux-kernel@vger.kernel.org, rcu@vger.kernel.org, cgroups@vger.kernel.org, Qiliang Yuan References: <20260421030351.281436-1-longman@redhat.com> <20260624063404.2106807-1-realwujing@gmail.com> Content-Language: en-US From: Waiman Long In-Reply-To: <20260624063404.2106807-1-realwujing@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 On 6/24/26 2:34 AM, Jing Wu wrote: > Hi Waiman, > > Thomas Gleixner suggested we coordinate, so reaching out directly. > > We have been working on a similar feature called Dynamic Housekeeping > Management (DHM) [1][2][3][4]. The RFC was posted on 2026-02-06, v1 on > 2026-03-25, and v2 on 2026-04-13 — a week before your series appeared. > It seems we developed these independently in parallel. > > After Thomas's review of DHM v3, we are rebuilding v4 around the > CPU-by-CPU offline/online hotplug mechanism, which aligns with the > direction of your series. > > There is one key difference in scope worth discussing: > > Your series requires "nohz_full=" to be present at boot (even with > an empty CPU list) to opt into runtime updates. DHM targets systems > where nohz_full= was never configured at boot — enabling CPU noise > isolation purely at runtime without any boot-time setup. > > This requires making the nohz_full infrastructure activatable at > runtime for the first time, rather than just extending an already- > initialized boot configuration. > > Before we start coding v4, a few questions: > > 1. Are you planning a v2 of your series? If so, what is your > timeline? We want to avoid duplicating effort on the subsystem > patches (tick, RCU, genirq). Yes, I am planning to send out a v2 in a few weeks depending on whether I can finish the other works that I am doing right now. > > 2. Would you be open to extending your series to cover the > "no boot parameter" use case, or do you think it is better kept > as a separate series? The reason to make the v1 series depending on the nohz_full parameter is basically a short cut as some code will change its behavior slightly depending on if the nohz_full parameter is set. By making it optional, we just have to add more code to enable them. It is more work, but doable. I will make that optional in the next version, but I probably won't have all the needed code other than the essential ones and the rests will be handled in a followup patch series. > > 3. Are there specific patches in your series where you would welcome > our contribution directly? I have broken down the shutdown callback into separate portions as suggested by Thomas. The other major change that I am working on is to try to shutdown to only CPUHP_AP_OFFLINE state instead of all the way down to CPUHP_OFFLINE. That will require some adjustments to the nohz_full related hotplug functions. I have some ideas of what needs to be done. However, I haven't looked into RCU yet. I know RCU support changing the nocb mask for fully offline CPUs, I will need to find out if it possible to do that for partially offline CPUs. The work has been suspended for a while as I have other works to do. Hopefully I can restart it soon to further refresh my memory and we can discuss collaboration at that point. Cheers, Longman > > Happy to collaborate on a unified approach. > > [1] DHM RFC (2026-02-06): https://lore.kernel.org/r/20260206-feature-dynamic_isolcpus_dhei-v1-0-00a711eb0c74@gmail.com > [2] DHM v1 (2026-03-25): https://lore.kernel.org/r/20260325-dhei-v12-final-v1-0-919cca23cadf@gmail.com > [3] DHM v2 (2026-04-13): https://lore.kernel.org/r/20260413-wujing-dhm-v2-0-06df21caba5d@gmail.com > [4] DHM v3 (2026-06-18): https://lore.kernel.org/r/20260618-wujing-dhm-v3-0-28f1a4d83b68@gmail.com > [5] Your series v1 (2026-04-20): https://lore.kernel.org/r/20260421030351.281436-1-longman@redhat.com > > Jing Wu > Qiliang Yuan >