From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932853AbdGXVg7 (ORCPT ); Mon, 24 Jul 2017 17:36:59 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:35988 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751969AbdGXVgc (ORCPT ); Mon, 24 Jul 2017 17:36:32 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 1/6] documentation: Fix relation between nohz_full and rcu_nocbs Date: Mon, 24 Jul 2017 14:36:23 -0700 X-Mailer: git-send-email 2.5.2 In-Reply-To: <20170724213605.GA8766@linux.vnet.ibm.com> References: <20170724213605.GA8766@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 17072421-0044-0000-0000-00000372B917 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007419; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000214; SDB=6.00892369; UDB=6.00446020; IPR=6.00672534; BA=6.00005489; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00016356; XFM=3.00000015; UTC=2017-07-24 21:36:30 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17072421-0045-0000-0000-000007A0C361 Message-Id: <1500932188-9202-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-07-24_13:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=1 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1706020000 definitions=main-1707240328 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If a CPU is specified in the nohz_full= kernel boot parameter to a kernel built with CONFIG_NO_HZ_FULL=y, then that CPU's callbacks will be offloaded, just as if that CPU had also been specified in the rcu_nocbs= kernel boot parameter. But the current documentation states that the user must keep these two boot parameters manually synchronized. This commit therefore updates the documentation to reflect reality. Signed-off-by: Paul E. McKenney --- Documentation/admin-guide/kernel-parameters.txt | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index d9c171ce4190..3a99cc96b6b1 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2633,9 +2633,10 @@ In kernels built with CONFIG_NO_HZ_FULL=y, set the specified list of CPUs whose tick will be stopped whenever possible. The boot CPU will be forced outside - the range to maintain the timekeeping. - The CPUs in this range must also be included in the - rcu_nocbs= set. + the range to maintain the timekeeping. Any CPUs + in this list will have their RCU callbacks offloaded, + just as if they had also been called out in the + rcu_nocbs= boot parameter. noiotrap [SH] Disables trapped I/O port accesses. -- 2.5.2