From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753209Ab2INV4d (ORCPT ); Fri, 14 Sep 2012 17:56:33 -0400 Received: from casper.infradead.org ([85.118.1.10]:43761 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751163Ab2INV4c convert rfc822-to-8bit (ORCPT ); Fri, 14 Sep 2012 17:56:32 -0400 Message-ID: <1347659777.7172.97.camel@twins> Subject: Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to 3.6-rc5 on AMD chipsets - bisected From: Peter Zijlstra To: Linus Torvalds Cc: Borislav Petkov , Nikolay Ulyanitsky , Mike Galbraith , linux-kernel@vger.kernel.org, Andreas Herrmann , Andrew Morton , Thomas Gleixner , Ingo Molnar Date: Fri, 14 Sep 2012 23:56:17 +0200 In-Reply-To: References: <20120914212717.GA29307@liondog.tnic> <1347658843.7172.90.camel@twins> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2012-09-14 at 14:44 -0700, Linus Torvalds wrote: > On Fri, Sep 14, 2012 at 2:40 PM, Peter Zijlstra wrote: > > > > The problem the patch is trying to address is not having to scan an > > entire package for idle cores on every wakeup now that packages are > > getting stupid big. > > No, it does something *else* too. That whole "left-right" logic to > (according to the commit message) "prevent bouncing" is entirely new, > afaik. > > So it is *not* just about avoiding to have to scan the whole package. > It changes actual semantics too. No? Both things change semantics, not looking at the entire package is new too. But yeah I guess you could look at the exact cross-stitching as an enhancement to the 'idle_buggy' thing.