From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH v3] lockdep: Make MAX_STACK_TRACE_ENTRIES configurable. Date: Wed, 21 Apr 2010 14:03:00 +0200 Message-ID: <1271851380.1776.96.camel@laptop> References: <20100420140941.d085007d.akpm@linux-foundation.org> <1271849823.1776.87.camel@laptop> <4BCEAD7B0200005A0006513E@soto.provo.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: John Kacur , Ingo Molnar , Thomas Gleixner , Andrew Morton , "Luis Claudio R. Goncalves" , Clark Williams , linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org To: Gregory Haskins Return-path: Received: from bombadil.infradead.org ([18.85.46.34]:39388 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752940Ab0DUMDF (ORCPT ); Wed, 21 Apr 2010 08:03:05 -0400 Received: from f199130.upc-f.chello.nl ([80.56.199.130] helo=dyad.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.69 #1 (Red Hat Linux)) id 1O4Ydz-0004Uh-76 for linux-rt-users@vger.kernel.org; Wed, 21 Apr 2010 12:03:03 +0000 In-Reply-To: <4BCEAD7B0200005A0006513E@soto.provo.novell.com> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Wed, 2010-04-21 at 05:47 -0600, Gregory Haskins wrote: > > I am not sure if Johns solution is the right/best one per se, but I can attest > that I used to hit this problem _all_ the time and it was somewhat annoying > to need to patch the kernel on all of my machines to fix it. I realize that I > perhaps do not represent the average user, but it was a pain-point for me. > FWIW, John's patch would indeed make my life easier since I tend to share the > .config between builds. Right, so all I'm wanting to know if its a symptom of some funny or an actual depletion, in the latter case I think the best solution is to simply increase the number. In the former case we should of course fix the real issue instead of making it disappear. So one case I remember is where some code managed to create 1k classes where 1 would have sufficed, this resulted in at least 1k extra stack traces to be stored, consuming vast amounts of stack_entries. So please, if you can reproduce, look at where these entries are going, lots of classes with the same name are a good hint that something is fishy. Classes with more than 13 (4*nr_states + 1) stacks should also never happen, etc.. Is this specific to -RT, or do we see it without as well? If so, what in -RT grows this? Are we creating a class per rt_mutex spinlock or something silly like that?