From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754388Ab2AaNbF (ORCPT ); Tue, 31 Jan 2012 08:31:05 -0500 Received: from casper.infradead.org ([85.118.1.10]:51633 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753343Ab2AaNbD (ORCPT ); Tue, 31 Jan 2012 08:31:03 -0500 Date: Tue, 31 Jan 2012 05:32:36 -0800 From: Arjan van de Ven To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, x86@kernel.org, arjanvandeven@gmail.com, Thomas Gleixner , Peter Zijlstra Subject: Re: x86: clean up smpboot.c's use of udelay+schedule Message-ID: <20120131053236.3f120f11@infradead.org> In-Reply-To: <20120131124341.GC4408@elte.hu> References: <20120130205304.0e10b05e@infradead.org> <20120131124341.GC4408@elte.hu> Organization: Intel X-Mailer: Claws Mail 3.7.9 (GTK+ 2.24.7; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 31 Jan 2012 13:43:41 +0100 Ingo Molnar wrote: > > + usleep_range(100, 200); > > I'm wondering whether we could shorten this delay to say 10 > usecs and thus save 0.1 msecs (or more) from a typical SMP > bootup? doesn't matter really; bringing up a cpu is several orders more expensive (> 100msec in 3.2, in 3.3 this got optimized to maybe 30 msec) 0.1 msec is the least of anyone's worries at this point ;-) (would be nice if this was a completion, but this is rather fragile code in general... at least not making it spin is an incremental improvement)