From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932660Ab3BLKLh (ORCPT ); Tue, 12 Feb 2013 05:11:37 -0500 Received: from merlin.infradead.org ([205.233.59.134]:59516 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755527Ab3BLKLg (ORCPT ); Tue, 12 Feb 2013 05:11:36 -0500 Message-ID: <1360663879.4485.2.camel@laptop> Subject: Re: [patch v4 01/18] sched: set SD_PREFER_SIBLING on MC domain to reduce a domain level From: Peter Zijlstra To: Alex Shi Cc: torvalds@linux-foundation.org, mingo@redhat.com, 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, viresh.kumar@linaro.org, linux-kernel@vger.kernel.org Date: Tue, 12 Feb 2013 11:11:19 +0100 In-Reply-To: <1358996820-23036-2-git-send-email-alex.shi@intel.com> References: <1358996820-23036-1-git-send-email-alex.shi@intel.com> <1358996820-23036-2-git-send-email-alex.shi@intel.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.2- Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2013-01-24 at 11:06 +0800, Alex Shi wrote: > The domain flag SD_PREFER_SIBLING was set both on MC and CPU domain at > frist commit b5d978e0c7e79a, and was removed uncarefully when clear up > obsolete power scheduler. Then commit 6956dc568 recover the flag on CPU > domain only. It works, but it introduces a extra domain level since this > cause MC/CPU different. > > So, recover the the flag in MC domain too to remove a domain level in > x86 platform. This fails to clearly state why its desirable.. I'm guessing its because we should use sibling cache domains before sibling threads, right? A clearly stated reason is always preferable over: it was this way, make it so again; which leaves us wondering why.