Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754138AbZIHJuW (ORCPT ); Tue, 8 Sep 2009 05:50:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753993AbZIHJuV (ORCPT ); Tue, 8 Sep 2009 05:50:21 -0400 Received: from gate.crashing.org ([63.228.1.57]:55917 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753974AbZIHJuV (ORCPT ); Tue, 8 Sep 2009 05:50:21 -0400 Subject: Re: BFS vs. mainline scheduler benchmarks and measurements From: Benjamin Herrenschmidt To: Ingo Molnar Cc: Michael Buesch , Con Kolivas , linux-kernel@vger.kernel.org, Peter Zijlstra , Mike Galbraith , Felix Fietkau In-Reply-To: <20090908074825.GA11413@elte.hu> References: <20090906205952.GA6516@elte.hu> <200909071716.57722.mb@bu3sch.de> <20090907182629.GA3484@elte.hu> <20090908074825.GA11413@elte.hu> Content-Type: text/plain Date: Tue, 08 Sep 2009 19:50:00 +1000 Message-Id: <1252403400.4950.81.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1287 Lines: 30 On Tue, 2009-09-08 at 09:48 +0200, Ingo Molnar wrote: > So either your MIPS system has some unexpected dependency on the > scheduler, or there's something weird going on. > > Mind poking on this one to figure out whether it's all repeatable > and why that slowdown happens? Multiple attempts to reproduce it > failed here for me. Could it be the scheduler using constructs that don't do well on MIPS ? I remember at some stage we spotted an expensive multiply in there, maybe there's something similar, or some unaligned or non-cache friendly vs. the MIPS cache line size data structure, that sort of thing ... Is this a SW loaded TLB ? Does it misses on kernel space ? That could also be some differences in how many pages are touched by each scheduler causing more TLB pressure. This will be mostly invisible on x86. At this stage, it will be hard to tell without some profile data I suppose. Maybe next week I can try on a small SW loaded TLB embedded PPC see if I can reproduce some of that, but no promises here. Cheers, Ben. -- 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/