From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966302AbcIWOeW (ORCPT ); Fri, 23 Sep 2016 10:34:22 -0400 Received: from merlin.infradead.org ([205.233.59.134]:49686 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965954AbcIWOeV (ORCPT ); Fri, 23 Sep 2016 10:34:21 -0400 Date: Fri, 23 Sep 2016 16:34:13 +0200 From: Peter Zijlstra To: Babu Moger 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 Subject: Re: [PATCH 0/2] Ajust lockdep static allocations Message-ID: <20160923143413.GM5008@twins.programming.kicks-ass.net> References: <1474569816-170269-1-git-send-email-babu.moger@oracle.com> <20160923071246.GJ2794@worktop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. In any case, maybe invert this, add make it depend on CONFIG_BASE_SMALL, since this really only matters for really dinky systems.