From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757618Ab3K1QtK (ORCPT ); Thu, 28 Nov 2013 11:49:10 -0500 Received: from mga02.intel.com ([134.134.136.20]:2659 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751045Ab3K1QtH (ORCPT ); Thu, 28 Nov 2013 11:49:07 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.93,791,1378882800"; d="scan'208";a="443769161" Message-ID: <529773FC.6020707@linux.intel.com> Date: Thu, 28 Nov 2013 18:49:00 +0200 From: Eliezer Tamir User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.1.1 MIME-Version: 1.0 To: Peter Zijlstra , Arjan van de Ven , lenb@kernel.org, rjw@rjwysocki.net, David Miller , rui.zhang@intel.com, jacob.jun.pan@linux.intel.com, Mike Galbraith , Ingo Molnar , hpa@zytor.com, Thomas Gleixner CC: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH 7/8] sched, net: Fixup busy_loop_us_clock() References: <20131126155743.116756708@infradead.org> <20131126160815.293633156@infradead.org> In-Reply-To: <20131126160815.293633156@infradead.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26/11/2013 17:57, Peter Zijlstra wrote: > > Replace sched_clock() usage with local_clock() which has a bounded > drift between CPUs (<2 jiffies). > Peter, I have tested this patch and I see a performance regression of about 1.5%. Maybe it would be better, rather then testing in the fast path, to simply disallow busy polling altogether when sched_clock_stable is not true? Thanks, Eliezer