From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750828AbWDSAaj (ORCPT ); Tue, 18 Apr 2006 20:30:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750941AbWDSAaj (ORCPT ); Tue, 18 Apr 2006 20:30:39 -0400 Received: from mail.suse.de ([195.135.220.2]:38074 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S1750828AbWDSAaj (ORCPT ); Tue, 18 Apr 2006 20:30:39 -0400 To: Robin Holt Cc: tony.luck@intel.com, linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: ia64_do_page_fault shows 19.4% slowdown from notify_die. References: <20060417112552.GB4929@lnx-holt.americas.sgi.com> <9758.1145319832@ocs3.ocs.com.au> <20060418221623.GB22514@lnx-holt.americas.sgi.com> From: Andi Kleen Date: 19 Apr 2006 02:30:35 +0200 In-Reply-To: <20060418221623.GB22514@lnx-holt.americas.sgi.com> Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Robin Holt writes: > 499 nSec/fault ia64_do_page_fault notify_die commented out. > 501 nSec/fault ia64_do_page_fault with nobody registered. > 533 nSec/fault notify_die in and just kprobes. > 596 nSec/fault notify_die in and kdb, kprobes, mca, and xpc loaded. > > The 596 nSec/fault is a 19.4% slowdown. This is an upcoming OSD beta > kernel. It will be representative of what our typical customer will > have loaded. With kdb some slowdown is expected. But just going through kprobes shouldn't be that slow. I guess there would be optimization potential there. Do you have finer grained profiling what is actually slow? > Having the notify_page_fault() without anybody registered was only a > 0.4% slowdown. I am not sure that justifies the optimize away, but I > would certainly not object. Still sounds far too much for what is essentially a call + load + test + return Where is that overhead comming from? I know IA64 doesn't like indirect calls, but there shouldn't any be there for this case. -Andi