From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760509AbcIWOvg (ORCPT ); Fri, 23 Sep 2016 10:51:36 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:23371 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752083AbcIWOvd (ORCPT ); Fri, 23 Sep 2016 10:51:33 -0400 Subject: Re: [PATCH 0/2] Ajust lockdep static allocations To: Peter Zijlstra References: <1474569816-170269-1-git-send-email-babu.moger@oracle.com> <20160923071246.GJ2794@worktop> <20160923143413.GM5008@twins.programming.kicks-ass.net> Cc: mingo@redhat.com, akpm@linux-foundation.org, keescook@chromium.org, dan.j.williams@intel.com, aryabinin@virtuozzo.com, tj@kernel.org, linux-kernel@vger.kernel.org From: Babu Moger Organization: Oracle Corporation Message-ID: <71daf047-059d-3478-9e08-989d44211a9c@oracle.com> Date: Fri, 23 Sep 2016 09:50:52 -0500 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <20160923143413.GM5008@twins.programming.kicks-ass.net> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: aserv0021.oracle.com [141.146.126.233] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/23/2016 9:34 AM, Peter Zijlstra wrote: > On Fri, Sep 23, 2016 at 09:04:42AM -0500, Babu Moger wrote: >> On 9/23/2016 2:12 AM, Peter Zijlstra wrote: >>> On Thu, Sep 22, 2016 at 11:43:34AM -0700, Babu Moger wrote: >>>> These patches adjust the static allocations for lockdep >>>> data structures used for debugging locking correctness. The current >>>> code reserves about 4MB extra space for these data structures. Most >>>> of the configurations do not need these many data structures. While >>>> testing, I have not seen it go beyond 20% of already reserved entries. >>>> >>>> $grep "lock-classes" /proc/lockdep_stats >>>> lock-classes: 1560 [max: 8191] >>>> >>>> Reserving even more space seems unreasonable. So, keeping the default >>>> entries small as before the Commit 1413c0389333 ("lockdep: Increase static >>>> allocations"). Added new CONFIG_PROVE_LOCKING_PLUS in case someone >>>> needs more entries to debug their large configuration. >>> Why make this more complicated? There's absolutely no upside to this >>> change as far as I can see. >> Peter, What do you mean? > I mean I see no point to the patches you send. > >> Revert the commit 1413c038933? > Nah, why would I? > >> Right now, I cannot boot my setup after enabling lockdep. How do you >> think we can handle this? > Why can't you boot? You have that little memories? 4MB doesn't seem like > a worthwhile amount of memory. > > Also, you didn't say. This seems a somewhat crucial point. Correct, We can't boot with lockdep. Sorry I did not make that clear. We have a limit on static size of the kernel. > > In any case, maybe invert this, add make it depend on CONFIG_BASE_SMALL, > since this really only matters for really dinky systems. Sure. Will use CONFIG_BASE_SMALL and re-post the patches. Thanks >