From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: Re: [RFC PATCH 0/5] futex: introduce an optimistic spinning futex Date: Tue, 22 Jul 2014 15:36:15 -0400 Message-ID: <53CEBD2F.2040705@hp.com> References: <1405956271-34339-1-git-send-email-Waiman.Long@hp.com> <20140721211801.GA12149@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140721211801.GA12149-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ingo Molnar Cc: Thomas Gleixner , Peter Zijlstra , Darren Hart , Davidlohr Bueso , Heiko Carstens , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jason Low , Scott J Norton List-Id: linux-api@vger.kernel.org On 07/21/2014 05:18 PM, Ingo Molnar wrote: > * 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 The performance can varies quite a bit depending on what other processes are running at the test execution time. I will include stddev data in the next iteration of the patch. -Longman