Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752718AbZKKNPE (ORCPT ); Wed, 11 Nov 2009 08:15:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752375AbZKKNPD (ORCPT ); Wed, 11 Nov 2009 08:15:03 -0500 Received: from eddie.linux-mips.org ([78.24.191.182]:33340 "EHLO eddie.linux-mips.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752255AbZKKNPC (ORCPT ); Wed, 11 Nov 2009 08:15:02 -0500 Date: Wed, 11 Nov 2009 13:15:02 +0000 (GMT) From: "Maciej W. Rozycki" To: Wu Zhangjin cc: David Daney , linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, zhangfx@lemote.com, zhouqg@gmail.com, Ralf Baechle , rostedt@goodmis.org, Frederic Weisbecker , Ingo Molnar , Nicholas Mc Guire , Richard Sandiford , Patrik Kluba , Thomas Gleixner , Michal Simek Subject: Re: [PATCH v7 04/17] tracing: add static function tracer support for MIPS In-Reply-To: <1257907351.2922.37.camel@falcon.domain.org> Message-ID: References: <9dc81a7a9e5a292cccdf465c533a2b08d19d6021.1257779502.git.wuzhangjin@gmail.com> <8f579e2cece16cd22358a4ec143ef6a8c462639b.1257779502.git.wuzhangjin@gmail.com> <4AF8B31C.5030802@caviumnetworks.com> <1257814817.2822.3.camel@falcon.domain.org> <4AF99848.9090000@caviumnetworks.com> <1257907351.2922.37.camel@falcon.domain.org> User-Agent: Alpine 2.00 (LFD 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: 907 Lines: 21 On Wed, 11 Nov 2009, Wu Zhangjin wrote: > > -mlong-calls really degrades performance. I have seen things like 6% > > drop in network packet forwarding rates with -mlong-calls. > > > > so much drop? seems only two instructions added for it: lui, addi. from > this view point, I think the -fno-omit-frame-pointer(add, sd, move...) > will also bring with much drop. No, register jumps cannot be predicted -- this is where the performance goes on any serious processor -- the two extra instructions are nothing compared to that. OTOH frame pointer calculations are pure arithmetic, so you only lose time incurred by the instructions themselves. Maciej -- 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/