From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754587Ab3AKCp1 (ORCPT ); Thu, 10 Jan 2013 21:45:27 -0500 Received: from mga11.intel.com ([192.55.52.93]:31865 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751722Ab3AKCp0 (ORCPT ); Thu, 10 Jan 2013 21:45:26 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,447,1355126400"; d="scan'208";a="275625131" Message-ID: <50EF7D07.6080006@intel.com> Date: Fri, 11 Jan 2013 10:46:31 +0800 From: Alex Shi User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120912 Thunderbird/15.0.1 MIME-Version: 1.0 To: Morten Rasmussen CC: "mingo@redhat.com" , "peterz@infradead.org" , "tglx@linutronix.de" , "akpm@linux-foundation.org" , "arjan@linux.intel.com" , "bp@alien8.de" , "pjt@google.com" , "namhyung@kernel.org" , "efault@gmx.de" , "vincent.guittot@linaro.org" , "gregkh@linuxfoundation.org" , "preeti@linux.vnet.ibm.com" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v3 05/22] sched: remove domain iterations in fork/exec/wake References: <1357375071-11793-1-git-send-email-alex.shi@intel.com> <1357375071-11793-6-git-send-email-alex.shi@intel.com> <20130109182102.GC2046@e103034-lin> In-Reply-To: <20130109182102.GC2046@e103034-lin> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/10/2013 02:21 AM, Morten Rasmussen wrote: >> new_cpu = find_idlest_cpu(group, p, cpu); >> > - >> > - /* Now try balancing at a lower domain level of new_cpu */ >> > - cpu = new_cpu; >> > - weight = sd->span_weight; >> > - sd = NULL; >> > - for_each_domain(cpu, tmp) { >> > - if (weight <= tmp->span_weight) >> > - break; >> > - if (tmp->flags & sd_flag) >> > - sd = tmp; >> > - } >> > - /* while loop will break here if sd == NULL */ > I agree that this should be a major optimization. I just can't figure > out why the existing recursive search for an idle cpu switches to the > new cpu near the end and then starts a search for an idle cpu in the new > cpu's domain. Is this to handle some exotic sched domain configurations? > If so, they probably wouldn't work with your optimizations. I did not find odd configuration that asking for old logical. According to Documentation/scheduler/sched-domains.txt, Maybe never. "A domain's span MUST be a superset of it child's span (this restriction could be relaxed if the need arises), and a base domain for CPU i MUST span at least i." etc. etc. -- Thanks Alex