From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751728AbdJNIL3 (ORCPT ); Sat, 14 Oct 2017 04:11:29 -0400 Received: from mail-lf0-f47.google.com ([209.85.215.47]:46301 "EHLO mail-lf0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750970AbdJNILY (ORCPT ); Sat, 14 Oct 2017 04:11:24 -0400 X-Google-Smtp-Source: ABhQp+Sywkj/hOU/A1tOEWclHTyUqjh/zSzdEoFc7ZYLgMYh5Iu1OX4nX+5DZCXHbSDJu49drQjyaQ== Date: Sat, 14 Oct 2017 10:11:24 +0200 From: Johan Hovold To: Ingo Molnar Cc: Johan Hovold , Byungchul Park , Peter Zijlstra , linux-kernel@vger.kernel.org, tglx@linutronix.de, linux-mm@kvack.org, kernel-team@lge.com, Tony Lindgren , Arnd Bergmann , linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: Dramatic lockdep slowdown in 4.14 Message-ID: <20171014081124.GB16632@localhost> References: <20171013090333.GA17356@localhost> <20171014072659.f2yr6mhm5ha3eou7@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171014072659.f2yr6mhm5ha3eou7@gmail.com> User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Oct 14, 2017 at 09:26:59AM +0200, Ingo Molnar wrote: > > * Johan Hovold wrote: > > > Hi, > > > > I had noticed that the BeagleBone Black boot time appeared to have > > increased significantly with 4.14 and yesterday I finally had time to > > investigate it. > > > > Boot time (from "Linux version" to login prompt) had in fact doubled > > since 4.13 where it took 17 seconds (with my current config) compared to > > the 35 seconds I now see with 4.14-rc4. > > > > I quick bisect pointed to lockdep and specifically the following commit: > > > > 28a903f63ec0 ("locking/lockdep: Handle non(or multi)-acquisition > > of a crosslock") > > > > which I've verified is the commit which doubled the boot time (compared > > to 28a903f63ec0^) (added by lockdep crossrelease series [1]). > > > > I also verified that simply disabling CONFIG_PROVE_LOCKING on 4.14-rc4 > > brought boot time down to about 14 seconds. > > > > Now since it's lockdep I guess this can't really be considered a > > regression if these changes did improve lockdep correctness, but still, > > this dramatic slow down essentially forces me to disable PROVE_LOCKING > > by default on this system. > > > > Is this lockdep slowdown expected and desirable? > > It's not desirable at all. > > Does the patch below fix the regression for you - or does the introduction and > handling of ->nr_acquire hurt as well? > - select LOCKDEP_CROSSRELEASE > - select LOCKDEP_COMPLETIONS > +# select LOCKDEP_CROSSRELEASE > +# select LOCKDEP_COMPLETIONS Disabling these options this way gives me a about boot time of 17 seconds again, so yes, that fixes the problem. Thanks, Johan From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johan Hovold Subject: Re: Dramatic lockdep slowdown in 4.14 Date: Sat, 14 Oct 2017 10:11:24 +0200 Message-ID: <20171014081124.GB16632@localhost> References: <20171013090333.GA17356@localhost> <20171014072659.f2yr6mhm5ha3eou7@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20171014072659.f2yr6mhm5ha3eou7@gmail.com> Sender: owner-linux-mm@kvack.org To: Ingo Molnar Cc: Johan Hovold , Byungchul Park , Peter Zijlstra , linux-kernel@vger.kernel.org, tglx@linutronix.de, linux-mm@kvack.org, kernel-team@lge.com, Tony Lindgren , Arnd Bergmann , linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: linux-omap@vger.kernel.org On Sat, Oct 14, 2017 at 09:26:59AM +0200, Ingo Molnar wrote: > > * Johan Hovold wrote: > > > Hi, > > > > I had noticed that the BeagleBone Black boot time appeared to have > > increased significantly with 4.14 and yesterday I finally had time to > > investigate it. > > > > Boot time (from "Linux version" to login prompt) had in fact doubled > > since 4.13 where it took 17 seconds (with my current config) compared to > > the 35 seconds I now see with 4.14-rc4. > > > > I quick bisect pointed to lockdep and specifically the following commit: > > > > 28a903f63ec0 ("locking/lockdep: Handle non(or multi)-acquisition > > of a crosslock") > > > > which I've verified is the commit which doubled the boot time (compared > > to 28a903f63ec0^) (added by lockdep crossrelease series [1]). > > > > I also verified that simply disabling CONFIG_PROVE_LOCKING on 4.14-rc4 > > brought boot time down to about 14 seconds. > > > > Now since it's lockdep I guess this can't really be considered a > > regression if these changes did improve lockdep correctness, but still, > > this dramatic slow down essentially forces me to disable PROVE_LOCKING > > by default on this system. > > > > Is this lockdep slowdown expected and desirable? > > It's not desirable at all. > > Does the patch below fix the regression for you - or does the introduction and > handling of ->nr_acquire hurt as well? > - select LOCKDEP_CROSSRELEASE > - select LOCKDEP_COMPLETIONS > +# select LOCKDEP_CROSSRELEASE > +# select LOCKDEP_COMPLETIONS Disabling these options this way gives me a about boot time of 17 seconds again, so yes, that fixes the problem. Thanks, Johan -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 From: johan@kernel.org (Johan Hovold) Date: Sat, 14 Oct 2017 10:11:24 +0200 Subject: Dramatic lockdep slowdown in 4.14 In-Reply-To: <20171014072659.f2yr6mhm5ha3eou7@gmail.com> References: <20171013090333.GA17356@localhost> <20171014072659.f2yr6mhm5ha3eou7@gmail.com> Message-ID: <20171014081124.GB16632@localhost> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Sat, Oct 14, 2017 at 09:26:59AM +0200, Ingo Molnar wrote: > > * Johan Hovold wrote: > > > Hi, > > > > I had noticed that the BeagleBone Black boot time appeared to have > > increased significantly with 4.14 and yesterday I finally had time to > > investigate it. > > > > Boot time (from "Linux version" to login prompt) had in fact doubled > > since 4.13 where it took 17 seconds (with my current config) compared to > > the 35 seconds I now see with 4.14-rc4. > > > > I quick bisect pointed to lockdep and specifically the following commit: > > > > 28a903f63ec0 ("locking/lockdep: Handle non(or multi)-acquisition > > of a crosslock") > > > > which I've verified is the commit which doubled the boot time (compared > > to 28a903f63ec0^) (added by lockdep crossrelease series [1]). > > > > I also verified that simply disabling CONFIG_PROVE_LOCKING on 4.14-rc4 > > brought boot time down to about 14 seconds. > > > > Now since it's lockdep I guess this can't really be considered a > > regression if these changes did improve lockdep correctness, but still, > > this dramatic slow down essentially forces me to disable PROVE_LOCKING > > by default on this system. > > > > Is this lockdep slowdown expected and desirable? > > It's not desirable at all. > > Does the patch below fix the regression for you - or does the introduction and > handling of ->nr_acquire hurt as well? > - select LOCKDEP_CROSSRELEASE > - select LOCKDEP_COMPLETIONS > +# select LOCKDEP_CROSSRELEASE > +# select LOCKDEP_COMPLETIONS Disabling these options this way gives me a about boot time of 17 seconds again, so yes, that fixes the problem. Thanks, Johan