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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F2F78C433F5 for ; Mon, 14 Feb 2022 08:28:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241916AbiBNI2e (ORCPT ); Mon, 14 Feb 2022 03:28:34 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:52138 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233127AbiBNI2b (ORCPT ); Mon, 14 Feb 2022 03:28:31 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B3F8925C61 for ; Mon, 14 Feb 2022 00:28:23 -0800 (PST) Received: from dggpeml500020.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Jxy1G3SpdzZcCh; Mon, 14 Feb 2022 16:24:02 +0800 (CST) Received: from dggpeml500003.china.huawei.com (7.185.36.200) by dggpeml500020.china.huawei.com (7.185.36.88) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Mon, 14 Feb 2022 16:28:21 +0800 Received: from [10.174.177.173] (10.174.177.173) by dggpeml500003.china.huawei.com (7.185.36.200) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Mon, 14 Feb 2022 16:28:21 +0800 Message-ID: Date: Mon, 14 Feb 2022 16:28:20 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Content-Language: en-US To: , From: Yu Liao Subject: Question about nohz and sysidle CC: , Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.173] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpeml500003.china.huawei.com (7.185.36.200) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, I'm working on an issue about nohz. When NO_HZ_FULL is enabled, CPU 0 handles the timekeeping duty on behalf of all other CPUs, which means CPU 0 never stop tick even in sysidle state. This is a powersaving issue. I found Frederic's patchset (nohz: Support sysidle) in the below link. https://lore.kernel.org/all/1406569056-30217-1-git-send-email-fweisbec@gmail.com/ But these patches haven't been merged into mainline yet and sysidle state detection has been removed by commit fe5ac724d81a (rcu: Remove nohz_full full-system-idle state machine) as well. I tried Frederic's patches and it does work, why are we no longer working on stopping timekeeping duty when all full dynticks CPUs are idle? Thanks, Yu