Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755445AbaBTSPx (ORCPT ); Thu, 20 Feb 2014 13:15:53 -0500 Received: from merlin.infradead.org ([205.233.59.134]:42082 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753634AbaBTSPw (ORCPT ); Thu, 20 Feb 2014 13:15:52 -0500 Date: Thu, 20 Feb 2014 19:15:38 +0100 From: Peter Zijlstra To: Andi Kleen Cc: Vince Weaver , Dave Jones , Linux Kernel , Ingo Molnar , Paul Mackerras , Steven Rostedt , Jiri Olsa Subject: Re: x86_pmu_start WARN_ON. Message-ID: <20140220181538.GK9987@twins.programming.kicks-ass.net> References: <20140217152859.GF15586@twins.programming.kicks-ass.net> <20140219101949.GG15586@twins.programming.kicks-ass.net> <20140220100830.GN6835@laptop.programming.kicks-ass.net> <87r46xdbw4.fsf@tassilo.jf.intel.com> <20140220155416.GH9987@twins.programming.kicks-ass.net> <87mwhld72w.fsf@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87mwhld72w.fsf@tassilo.jf.intel.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 20, 2014 at 09:31:19AM -0800, Andi Kleen wrote: > Peter Zijlstra writes: > > > > It will; trace_printk() works without -pg, I think you didn't read the > > instructions very well. > > Ok, you enable and disable it again. I won't guess why you do that. To grow the trace buffers; it starts with just a few pages per cpu; once you switch to an actual tracer it allocates a sensible amount. You can grow it with another interface; but then I'd have to like remember what that was and how big the normal buffers are. Simply toggling between tracers is far easier. > > And there's a very good reason not to apply your patch; you can route > > the function tracer into perf, guess what happens when perf calls the > > function tracer again :-) > > How? I think by using the /debug/tracing/events/ftrace/function event, but I'm not actually sure, I've never used it nor did I write the code to do it. Jolsa did all that IIRC. All I know is that we had some 'fun' bugs around there sometime back. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/