From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1165424AbdDXGW2 (ORCPT ); Mon, 24 Apr 2017 02:22:28 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:45447 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1165382AbdDXGWX (ORCPT ); Mon, 24 Apr 2017 02:22:23 -0400 Date: Sun, 23 Apr 2017 23:22:20 -0700 From: "Paul E. McKenney" To: Mike Galbraith Cc: LKML Subject: Re: TREE_SRCU slows hotplug by factor ~16 Reply-To: paulmck@linux.vnet.ibm.com References: <1493002089.4145.7.camel@gmx.de> <20170424033250.GX3956@linux.vnet.ibm.com> <1493011484.4166.13.camel@gmx.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1493011484.4166.13.camel@gmx.de> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17042406-0048-0000-0000-00000167599C X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006964; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000208; SDB=6.00851681; UDB=6.00420878; IPR=6.00630474; BA=6.00005309; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00015150; XFM=3.00000013; UTC=2017-04-24 06:22:18 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17042406-0049-0000-0000-000040BCE0B9 Message-Id: <20170424062220.GZ3956@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-04-24_05:,, 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=8.0.1-1703280000 definitions=main-1704240106 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 24, 2017 at 07:24:44AM +0200, Mike Galbraith wrote: > On Sun, 2017-04-23 at 20:32 -0700, Paul E. McKenney wrote: > > On Mon, Apr 24, 2017 at 04:48:09AM +0200, Mike Galbraith wrote: > > > Greetings, > > > > > > Running Steven's hotplug stress script in tip w. CLASSIC_SRCU takes 55s > > > in my i4790 box, whereas TREE_SRCU takes over 16m. (Master with the > > > same config does it in 39s.. but then lockdep isn't enabled in master) > > > > That doesn't sound good... > > > > But exactly which version are you using? There were some 8x slowdowns > > earlier this week that have since been fixed. Also, how many CPUs are > > on your system? > > 4 cores+SMT, tip.yesterday_afternoon (precise!) was initial test point, > tip.this_morning (v4.11-rc7-955-g76f8909e1cd8) is still slow. OK, that is after the earlier fix! And modest in size as well. Assuming 4ms per TREE_SRCU synchronize_srcu(), I end up with the CLASSIC_SRCU doing a synchronize_srcu() every 200us or so, which I am having a hard time believing. But it does matter, because it controls what approach I take to fixing this. Could you please collect an ftrace (or whatever) showing the timestamp sequence of calls to synchronize_srcu(), synchronize_srcu_expedited(), and call_srcu() during the execution of the stress script? If it is easy to do, also the timestamp sequence of returns from synchronize_srcu() and synchronize_srcu_expedited()? Thanx, Paul