From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752292Ab1LSRKP (ORCPT ); Mon, 19 Dec 2011 12:10:15 -0500 Received: from mx1.redhat.com ([209.132.183.28]:41193 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751223Ab1LSRKM (ORCPT ); Mon, 19 Dec 2011 12:10:12 -0500 Date: Mon, 19 Dec 2011 18:04:47 +0100 From: Oleg Nesterov To: Steven Rostedt , Ingo Molnar , Andrew Morton Cc: Frederic Weisbecker , Jiri Olsa , Masami Hiramatsu , Seiji Aguchi , linux-kernel@vger.kernel.org Subject: [PATCH RESEND 0/2] tracing: signal tracepoints Message-ID: <20111219170447.GA31981@redhat.com> References: <20111121191920.GA24883@redhat.com> <1321905799.20742.20.camel@frodo> <20111121202110.GA27966@redhat.com> <1321912356.20742.24.camel@frodo> <20111122205239.GA20971@redhat.com> <1322848385.30977.50.camel@frodo> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1322848385.30977.50.camel@frodo> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Steven, sorry for delay... On 12/02, Steven Rostedt wrote: > > On Tue, 2011-11-22 at 21:52 +0100, Oleg Nesterov wrote: > > > > > Is "result" used for anything but tracepoints? When tracing is disabled, > > > the tracepoints should be just nops (when jump_label is enabled). Thus > > > tracing is very light. But if we are constantly calculating "result", > > > this is unused by those that don't use the tracing infrastructure, which > > > is 99.99% of all users. This is what I meant. > > > > Ah I see. I thought you dislike OVERFLOW_FAIL/LOSE_INFO namely. > > > > Of course, you are right. OTOH, this patch shaves 1058 bytes from > > .text. And without CONFIG_TRACE* gcc doesn't generate the extra code. > > I was just noting that when tracing is disabled (CONFIG_TRACE* is set, > like it is on distros, but tracing is not happening), that we have extra > code. We usually strive to have tracing configured into the kernel, but > produces no (actually as little as possible) overhead when not actively > tracing. Yes, yes, I see. But I do not see any alternative. Of course, instead of adding "int result" we could add more trace_signal_generate's into the code, but imho this is too ugly. And in fact I am not sure this means less overhead with CONFIG_TRACE* even if this code is nop'ed. > That said, you know this code much more than I do. If this isn't a fast > path, and spinning a few more CPU cycles and perhaps dirtying a few > cache lines floats your boat. I'm OK with this change. I simply do not know. I _think_ that the overhead is negligible, the extra calculating just adds a couple of "mov CONSTANT, REGISTER" insns. > > Oh. I simply do not know what can I do. Obviously, I'd like to avoid > > the new tracepoints in __send_signal(), imho this would be ugly. But > > the users want more info. > > > > OK. let me send the patch at least for review. May be someone will > > nack it authoritatively, in this case I can relax and forward the > > nack back to bugzilla ;) > > Again, if you don't think adding very slight overhead to this path is an > issue. Go ahead and add it. OK, thanks. The next question is, how can I add it ;) May be Ingo or Andrew could take these patches? Original signal tracepoints were routed via tip-tree... Add them both to TO:, lets see who is kinder. > > However, at least 2/2 looks very reasonable to me. In fact it looks > > almost like the bug-fix. > > 2/2 looks to have the extra overhead to. Is the bug fix just with the > trace point. > > Again, if you don't mind the overhead, then here: > > Acked-by: Steven Rostedt Thanks, included. Oleg.