From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752480Ab2LWXJI (ORCPT ); Sun, 23 Dec 2012 18:09:08 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42464 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752245Ab2LWXJH (ORCPT ); Sun, 23 Dec 2012 18:09:07 -0500 Date: Sun, 23 Dec 2012 21:08:48 -0200 From: Rafael Aquini To: Rik van Riel Cc: Steven Rostedt , David Daney , linux-kernel@vger.kernel.org, walken@google.com, lwoodman@redhat.com, jeremy@goop.org, Jan Beulich , Thomas Gleixner Subject: Re: [RFC PATCH 3/3] x86,smp: auto tune spinlock backoff delay factor Message-ID: <20121223230847.GC4186@x61.redhat.com> References: <20121221184940.103c31ad@annuminas.surriel.com> <20121221185147.4ae48ab5@annuminas.surriel.com> <50D5033A.2070309@gmail.com> <50D52037.60602@redhat.com> <20121222034910.GG27621@home.goodmis.org> <50D52FF8.1050104@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50D52FF8.1050104@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 21, 2012 at 10:58:48PM -0500, Rik van Riel wrote: > On 12/21/2012 10:49 PM, Steven Rostedt wrote: > >On Fri, Dec 21, 2012 at 09:51:35PM -0500, Rik van Riel wrote: > > >>However, since spinlock contention should not be the > >>usual state, and all a scalable lock does is make sure > >>that N+1 CPUs does not perform worse than N CPUs, using > >>scalable locks is a stop-gap measure. > >> > >>I believe a stop-gap measure should be kept as simple as > >>we can. I am willing to consider moving to a per-lock > >>delay factor if we can figure out an easy way to do it, > >>but I would like to avoid too much extra complexity... > > > >Rik, > > > >I like your solution. It's rather simple and simple solutions tend to > >end up being the closest to optimal. The more complex a solution gets, > >the more it starts chasing fireflies. > > >Anyway, I'd like to see this code tested, and more benchmarks run > >against it. > > Absolutely. I would love to see if this code actually > causes regressions anywhere. > > It is simple enough that I suspect it will not, but there > really is only one way to find out. > > The more people test this with different workloads on > different SMP systems, the better. > Great work Rik, I have a couple of small SMP systems I'll start to test with your patches, also I might be able to test this work after new year's eve on a big SMP box that seems to be facing a severe lock starvation issue due to the BUS saturation your work is aiming to reduce. Cheers! -- Rafael