From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [RFC PATCH 0/5] futex: introduce an optimistic spinning futex Date: Mon, 21 Jul 2014 23:18:01 +0200 Message-ID: <20140721211801.GA12149@gmail.com> References: <1405956271-34339-1-git-send-email-Waiman.Long@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1405956271-34339-1-git-send-email-Waiman.Long@hp.com> Sender: linux-kernel-owner@vger.kernel.org To: Waiman Long Cc: Thomas Gleixner , Peter Zijlstra , Darren Hart , Davidlohr Bueso , Heiko Carstens , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-doc@vger.kernel.org, Jason Low , Scott J Norton List-Id: linux-api@vger.kernel.org * Waiman Long wrote: > Testing done on a 4-socket Westmere-EX boxes with 40 cores (HT off) > showed the following performance data (average kops/s) with various > load factor (number of pause instructions) used in the critical > section using an userspace mutex microbenchmark. > > Threads Load Waiting Futex Spinning Futex %Change > ------- ---- ------------- -------------- ------- > 256 1 6894 8883 +29% > 256 10 3656 4912 +34% > 256 50 1332 4358 +227% > 256 100 792 2753 +248% > 10 1 6382 4838 -24% > 10 10 3614 4748 +31% > 10 50 1319 3900 +196% > 10 100 782 2459 +214% > 2 1 7905 7194 -9.0% > 2 10 4556 4717 +3.5% > 2 50 2191 4167 +90% > 2 100 1767 2407 +36% So the numbers look interesting - but it would be _really_ important to provide noise/sttdev figures in a sixth column as well (denoted in percentage units, not in benchmark units), so that we know how significant a particular speedup (or slowdown) is. Thanks, Ingo