From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754142AbYKRPNs (ORCPT ); Tue, 18 Nov 2008 10:13:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752700AbYKRPNj (ORCPT ); Tue, 18 Nov 2008 10:13:39 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:41174 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752799AbYKRPNi (ORCPT ); Tue, 18 Nov 2008 10:13:38 -0500 Date: Tue, 18 Nov 2008 16:13:26 +0100 From: Ingo Molnar To: Steven Rostedt Cc: Frederic Weisbecker , Linux Kernel Subject: Re: [PATCH 3/3] tracing/function-return-tracer: add the overrun field Message-ID: <20081118151326.GH30358@elte.hu> References: <4920D571.4050007@gmail.com> <20081117084923.GD28786@elte.hu> <4921BA25.3090704@gmail.com> <20081118084755.GK17838@elte.hu> <20081118145154.GC30358@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00,DNS_FROM_SECURITYSAGE autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] 0.0 DNS_FROM_SECURITYSAGE RBL: Envelope sender in blackholes.securitysage.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Steven Rostedt wrote: > > On Tue, 18 Nov 2008, Ingo Molnar wrote: > > > > > * Steven Rostedt wrote: > > > > > > > > On Tue, 18 Nov 2008, Ingo Molnar wrote: > > > > > > > > > > Ok I will try with 50. If there are still a lot and often missing > > > > > traces with this depth, perhaps should we consider a hybrid solution > > > > > between ret stack and trampolines? We could use the normal ret stack > > > > > on struct info for most common cases and the trampoline when we are > > > > > exceeding the depth.... > > > > > > > > dunno, trampolines make me feel uneasy. > > > > > > > > Could you set it to some really large value (200) and add a "max > > > > depth seen" variable perhaps, and see the maximum depth? > > > > > > Don't run that on a box you care about ;-) But hopefully the stacks > > > will not collide. This should also depend on IRQSTACKS. > > > > that reminds me: ti->ret_stack[] should be moved to task->ret_stack[]. > > That way we decouple its size from any kernel stack size limits. > > (thread-info resides at one end of the kernel stack, on x86) > > Yeah, I recommended that to Frederic to save space. But that can be > dangerous. Using task instead would be safer with the downside of > making the task struct even bigger. We almost never put new stuff into thread_info - we have the lockdep lock stack in the task structure too, for similar reasons. Ingo