Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752699Ab2E0OcK (ORCPT ); Sun, 27 May 2012 10:32:10 -0400 Received: from mailout-de.gmx.net ([213.165.64.22]:36607 "HELO mailout-de.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1750846Ab2E0OcH (ORCPT ); Sun, 27 May 2012 10:32:07 -0400 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX19oeDNcyPdo8F/wLTxCxhtKooNsNRa6Neyjxmd4to zkf3utqHizRsv3 Message-ID: <1338129122.7400.45.camel@marge.simpson.net> Subject: Re: [rfc][patch] select_idle_sibling() inducing bouncing on westmere From: Mike Galbraith To: Arjan van de Ven Cc: Peter Zijlstra , lkml , Suresh Siddha , Paul Turner , Andreas Herrmann Date: Sun, 27 May 2012 16:32:02 +0200 In-Reply-To: <1338128955.7400.43.camel@marge.simpson.net> References: <1337857490.7300.19.camel@marge.simpson.net> <1337865431.9783.148.camel@laptop> <1337865641.9783.149.camel@laptop> <1337926468.5415.48.camel@marge.simpson.net> <1338014259.7302.26.camel@marge.simpson.net> <1338017364.14636.9.camel@twins> <1338020834.7747.8.camel@marge.simpson.net> <1338110259.7678.77.camel@marge.simpson.net> <4FC2362A.8080503@linux.intel.com> <1338128955.7400.43.camel@marge.simpson.net> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1303 Lines: 28 On Sun, 2012-05-27 at 16:29 +0200, Mike Galbraith wrote: > On Sun, 2012-05-27 at 07:11 -0700, Arjan van de Ven wrote: > > On 5/27/2012 2:17 AM, Mike Galbraith wrote: > > > On Sat, 2012-05-26 at 10:27 +0200, Mike Galbraith wrote: > > >> Hohum, back to finding out what happened to cpufreq. > > > > > > Answer: nothing.. in mainline. > > > > > > I test performance habitually, so just never noticed how bad ondemand > > > sucks. In enterprise, I found the below, explaining why cores crank up > > > fine there, but not in mainline. Somebody thumped ondemand properly on > > > it's pointy head. > > > > > > But, check out the numbers below this, and you can see just how horrible > > > bouncing is when you add governor latency _on top_ of it. > > > > part of it is not ondemand, but cpufreq. > > cpufreq forces you to schedule a kernel thread to change cpu > > frequency... on the cpu that's already busy. > > God knows what the scehduler then does in terms of load balancing. (and yeah, I am lumping ondemand and cpufreq together, which is wrong) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/