From patchwork Thu Sep 1 13:14:34 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Leizhen (ThunderTown)" X-Patchwork-Id: 12962548 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 D0565C0502C for ; Thu, 1 Sep 2022 13:19:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233642AbiIANTT (ORCPT ); Thu, 1 Sep 2022 09:19:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38516 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234341AbiIANSt (ORCPT ); Thu, 1 Sep 2022 09:18:49 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 391AE7C30A; Thu, 1 Sep 2022 06:16:03 -0700 (PDT) Received: from dggpemm500020.china.huawei.com (unknown [172.30.72.56]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4MJM2D32LbzHnYY; Thu, 1 Sep 2022 21:14:12 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500020.china.huawei.com (7.185.36.49) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 1 Sep 2022 21:16:00 +0800 Received: from thunder-town.china.huawei.com (10.174.178.55) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 1 Sep 2022 21:16:00 +0800 From: Zhen Lei To: "Paul E . McKenney" , Frederic Weisbecker , Neeraj Upadhyay , "Josh Triplett" , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , , CC: Zhen Lei Subject: [PATCH v6 0/2] rcu/nocb: Delete local variable 'need_rcu_nocb_mask' in rcu_init_nohz() Date: Thu, 1 Sep 2022 21:14:34 +0800 Message-ID: <20220901131436.986-1-thunder.leizhen@huawei.com> X-Mailer: git-send-email 2.26.0.windows.1 MIME-Version: 1.0 X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org v5 --> v6: 1. Frist, update patch 1/2, so that, CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y takes effect only when there are no 'rcu_nocbs=' and 'nohz_full='. Retain the same semantics as the original. 2. Then, add patch 2/2, so that, CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y takes effect as long as there is no "rcu_nocbs=" boot parameter. This is suggested by Frederic Weisbecker. Test cases and test results as below: ---------------------------------------------------------------------- | CONFIG_NO_HZ_FULL | CONFIG_RCU_NOCB_CPU_DEFAULT_ALL | cmdline | ---------------------------------------------------------------------- 1) N | N | none | 2) N | N | rcu_nocbs=1-2 | 3) Y | N | nohz_full=2-3 | 4) Y | N | rcu_nocbs=1 nohz_full=3 | 5) Y | Y | none | 6) Y | Y | rcu_nocbs=1-2 | 7) Y | Y | nohz_full=2-3 | 8) Y | Y | rcu_nocbs=1 nohz_full=3 | ---------------------------------------------------------------------- dmesg | grep "Offload RCU callbacks" 1) none 2) Offload RCU callbacks from CPUs: 1-2. 3) Offload RCU callbacks from CPUs: 2-3. 4) Offload RCU callbacks from CPUs: 1,3. 5) Offload RCU callbacks from CPUs: 0-3. 6) Offload RCU callbacks from CPUs: 1-2. 7) Offload RCU callbacks from CPUs: 0-3. 8) Offload RCU callbacks from CPUs: 1,3. v4 --> v5: 1. Cancel eliminate rcu_state.nocb_is_setup. It is useful for case 1) below. Test cases and test results as below: ---------------------------------------------------------------------- | CONFIG_NO_HZ_FULL | CONFIG_RCU_NOCB_CPU_DEFAULT_ALL | cmdline | ---------------------------------------------------------------------- 1) N | N | none | 2) N | N | rcu_nocbs=1-2 | 3) Y | N | nohz_full=1-2 | 4) Y | Y | none | ---------------------------------------------------------------------- 1) [ 1018.082417] rcu-torture:--- End of test: SUCCESS (default) root@genericarmv8:~# dmesg | grep "Offload RCU callbacks" root@genericarmv8:~# zcat /proc/config.gz | grep NOCB CONFIG_RCU_NOCB_CPU=y # CONFIG_RCU_NOCB_CPU_DEFAULT_ALL is not set root@genericarmv8:~# zcat /proc/config.gz | grep NO_HZ_FULL # CONFIG_NO_HZ_FULL is not set root@genericarmv8:~# cat /proc/cmdline console=ttyS0 earlyprintk=serial root=/dev/sda rw 2) 3) 4) The same to v4. v3 --> v4: Fix a build warning. - struct cpumask *cpumask = NULL; + const struct cpumask *cpumask = NULL; v2 --> v3: 1. Eliminate rcu_state.nocb_is_setup 2. Update the code based on the above patch and commit b37a667c6242 ("rcu/nocb: Add an option to offload all CPUs on boot"). Test cases and test results as below: ---------------------------------------------------------------------- | CONFIG_NO_HZ_FULL | CONFIG_RCU_NOCB_CPU_DEFAULT_ALL | cmdline | ---------------------------------------------------------------------- 1) N | N | none | 2) N | N | rcu_nocbs=1-2 | 3) Y | N | nohz_full=1-2 | 4) Y | Y | none | ---------------------------------------------------------------------- 1) [ 1085.691770] rcu-torture:--- End of test: SUCCESS: (default) root@genericarmv8:~# dmesg | grep "Offload RCU callbacks" [ 0.000000] rcu: Offload RCU callbacks from CPUs: (none). root@genericarmv8:~# zcat /proc/config.gz | grep NOCB CONFIG_RCU_NOCB_CPU=y # CONFIG_RCU_NOCB_CPU_DEFAULT_ALL is not set root@genericarmv8:~# zcat /proc/config.gz | grep NO_HZ_FULL # CONFIG_NO_HZ_FULL is not set root@genericarmv8:~# cat /proc/cmdline console=ttyAMA0 root=/dev/vda2 crashkernel=256M@ee000000 2) [ 1022.532198] rcu-torture:--- End of test: SUCCESS: (default) root@genericarmv8:~# dmesg | grep "Offload RCU callbacks" [ 0.000000] rcu: Offload RCU callbacks from CPUs: 1-2. root@genericarmv8:~# zcat /proc/config.gz | grep NOCB CONFIG_RCU_NOCB_CPU=y # CONFIG_RCU_NOCB_CPU_DEFAULT_ALL is not set root@genericarmv8:~# zcat /proc/config.gz | grep NO_HZ_FULL # CONFIG_NO_HZ_FULL is not set root@genericarmv8:~# cat /proc/cmdline console=ttyAMA0 root=/dev/vda2 crashkernel=256M@ee000000 rcu_nocbs=1-2 3) [ 1011.714712] rcu-torture:--- End of test: SUCCESS: (default) root@genericarmv8:~# dmesg | grep "Offload RCU callbacks" [ 0.000000] rcu: Offload RCU callbacks from CPUs: 1-2. root@genericarmv8:~# zcat /proc/config.gz | grep NOCB CONFIG_RCU_NOCB_CPU=y # CONFIG_RCU_NOCB_CPU_DEFAULT_ALL is not set root@genericarmv8:~# zcat /proc/config.gz | grep NO_HZ_FULL CONFIG_NO_HZ_FULL=y root@genericarmv8:~# cat /proc/cmdline console=ttyAMA0 root=/dev/vda2 crashkernel=256M@ee000000 nohz_full=1-2 4) [ 1031.047094] rcu-torture:--- End of test: SUCCESS: (default) root@genericarmv8:~# dmesg | grep "Offload RCU callbacks" [ 0.000000] rcu: Offload RCU callbacks from CPUs: 0-3. root@genericarmv8:~# zcat /proc/config.gz | grep NOCB CONFIG_RCU_NOCB_CPU=y CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y root@genericarmv8:~# zcat /proc/config.gz | grep NO_HZ_FULL CONFIG_NO_HZ_FULL=y root@genericarmv8:~# cat /proc/cmdline console=ttyAMA0 root=/dev/vda2 crashkernel=256M@ee000000 v1 --> v2: Update commit message. Zhen Lei (2): rcu: Simplify rcu_init_nohz() cpumask handling rcu: Offload callback processing from all CPUs in the absence of rcu_nocbs= kernel/rcu/Kconfig | 4 ++-- kernel/rcu/tree_nocb.h | 35 ++++++++++++----------------------- 2 files changed, 14 insertions(+), 25 deletions(-)