Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752483AbZDQT6N (ORCPT ); Fri, 17 Apr 2009 15:58:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751273AbZDQT56 (ORCPT ); Fri, 17 Apr 2009 15:57:58 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:58923 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751192AbZDQT55 (ORCPT ); Fri, 17 Apr 2009 15:57:57 -0400 Date: Fri, 17 Apr 2009 15:57:55 -0400 (EDT) From: Steven Rostedt X-X-Sender: rostedt@gandalf.stny.rr.com To: Ingo Molnar cc: Jeremy Fitzhardinge , Mathieu Desnoyers , Linux Kernel Mailing List , Jeremy Fitzhardinge Subject: Re: [PATCH 1/4] tracing: move __DO_TRACE out of line In-Reply-To: <20090417194613.GA30544@elte.hu> Message-ID: References: <1239950139-1119-1-git-send-email-jeremy@goop.org> <1239950139-1119-2-git-send-email-jeremy@goop.org> <20090417154640.GB8253@elte.hu> <20090417161005.GA16361@Krystal> <20090417162326.GG8253@elte.hu> <49E8D91F.1060005@goop.org> <20090417194613.GA30544@elte.hu> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1217 Lines: 35 On Fri, 17 Apr 2009, Ingo Molnar wrote: > > * Jeremy Fitzhardinge wrote: > > > Taking __do_trace_sched_switch out of lines inserts this into the > > hot path (6 instructions, 31 bytes): > > > > cmpl $0, __tracepoint_sched_switch+8(%rip) #, __tracepoint_sched_switch.state > > je .L1748 #, > > movq -136(%rbp), %rdx # next, > > movq -144(%rbp), %rsi # prev, > > movq %rbx, %rdi # rq, > > call __do_trace_sched_switch # > > .L1748: > > Hm, why isnt this off-line in the function? It's marked unlikely(), > isnt it? > > also, did you investigate the effect on the _instrumented_ function > itself? (i.e. the non-tracing related bits) A function call clobbers > various registers and creates pressure on gcc to shuffle registers > around. I doubt it will make much difference. The inline version stil has the function call to the trace point handler. -- Steve -- 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/