From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755286AbdDLUCj (ORCPT ); Wed, 12 Apr 2017 16:02:39 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:59698 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754599AbdDLUCh (ORCPT ); Wed, 12 Apr 2017 16:02:37 -0400 Date: Wed, 12 Apr 2017 13:02:31 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: linux-kernel@vger.kernel.org Subject: Re: There is a Tasks RCU stall warning Reply-To: paulmck@linux.vnet.ibm.com References: <20170411181530.27dc21cc@gandalf.local.home> <20170411230154.GA3956@linux.vnet.ibm.com> <20170411230445.GA25951@linux.vnet.ibm.com> <20170411231138.GB25951@linux.vnet.ibm.com> <20170412144800.GA12365@linux.vnet.ibm.com> <20170412105937.43175471@gandalf.local.home> <20170412162754.GJ3956@linux.vnet.ibm.com> <20170412125722.5f9a974a@gandalf.local.home> <20170412170716.GK3956@linux.vnet.ibm.com> <20170412131325.7c18389d@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170412131325.7c18389d@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17041220-0008-0000-0000-000001F27FE2 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006924; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000208; SDB=6.00846651; UDB=6.00417636; IPR=6.00625088; BA=6.00005286; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00015025; XFM=3.00000013; UTC=2017-04-12 20:02:34 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17041220-0009-0000-0000-0000349814E2 Message-Id: <20170412200231.GL3956@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-04-12_15:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1702020001 definitions=main-1704120163 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 12, 2017 at 01:13:25PM -0400, Steven Rostedt wrote: > On Wed, 12 Apr 2017 10:07:16 -0700 > "Paul E. McKenney" wrote: > > > > > > OK, will optimize it a bit. When are you planning to get this in? > > > > > > > > > > Well, I added the use case for synchronize_rcu_tasks() in my current > > > for-next. I'll have to make sure I get the schedule_idle() in as well > > > as my update to the event benchmark thread as well. > > > > > > I don't think anything will truly break without it yet. But that's > > > assuming there's not another kernel thread somewhere that just spins > > > calling schedule. > > > > > > And this patch will still speed up those that do call > > > synchronize_rcu_tasks(). But that's an optimization and not really a > > > fix. > > > > The upcoming v4.12 merge window, then? > > Yep. Also, is the default 10-minute stall warning OK? For purposes of comparison, when running rcutorture, Tasks RCU grace periods take 2-3 seconds, but of course your mileage may vary. For whatever it is worth, I set the default ratio of the Tasks RCU stall-warning time to its average rcutorture grace period to be about the same as the ratio for other RCU flavors. And the kernel boot parameter rcupdate.rcu_task_stall_timeout allows you to set whatever time you want (in jiffies) at boot time. And also modify it at runtime via sysfs. Thanx, Paul