From owner-freebsd-stable@FreeBSD.ORG Thu Apr 15 04:21:41 2010 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C8AE5106564A for ; Thu, 15 Apr 2010 04:21:41 +0000 (UTC) (envelope-from smithi@nimnet.asn.au) Received: from sola.nimnet.asn.au (paqi.nimnet.asn.au [115.70.110.159]) by mx1.freebsd.org (Postfix) with ESMTP id 147F38FC19 for ; Thu, 15 Apr 2010 04:21:40 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by sola.nimnet.asn.au (8.14.2/8.14.2) with ESMTP id o3F4LU4e090261; Thu, 15 Apr 2010 14:21:30 +1000 (EST) (envelope-from smithi@nimnet.asn.au) Date: Thu, 15 Apr 2010 14:21:30 +1000 (EST) From: Ian Smith To: Garrett Cooper In-Reply-To: Message-ID: <20100415135034.J52200@sola.nimnet.asn.au> References: <20100414.082109.29593248145846106.chat95@mac.com> <4BC5DEB4.1090208@freebsd.org> <20100415.094643.450985660335296086.chat95@mac.com> MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="0-1044302204-1271305290=:52200" Cc: amvandemore@gmail.com, Maho NAKATA , freebsd-stable@freebsd.org, alc@freebsd.org, alan.l.cox@gmail.com, avg@freebsd.org, als@modulus.org Subject: Re: HyperThreading makes worse to me (was Re: How to reproduce: Re: Only 70% of theoretical peak performance on FreeBSD 8/amd64, Corei7 920) X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 15 Apr 2010 04:21:41 -0000 This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --0-1044302204-1271305290=:52200 Content-Type: TEXT/PLAIN; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT On Wed, 14 Apr 2010, Garrett Cooper wrote: > On Wed, Apr 14, 2010 at 7:49 PM, Garrett Cooper wrote: > > On Wed, Apr 14, 2010 at 5:46 PM, Maho NAKATA wrote: > >> Hi Andry and Adam > >> > >> My test again. No desktop, etc. I just run dgemm. > >> Contrary to Adam's result, Hyper Threading makes the performance worse. > >> all tests are done on Core i7 920 @ 2.67GHz. (TurboBoost @2.8GHz) > >> > >> Turbo Boost off, Hyper threading off: 82% (35GFlops)    [1] > >> Turbo Boost off, Hyper threading off: 72% (30.5GFlops)  [2] Er, shouldn't one of those say HTT on? and/or Turbo boost on? Else they're both the same test as [4] but with different results? > >> Turbo Boost on,  Hyper threading on: 71% (32GFlops)    [3] > >> Turbo Boost off, Hyper threading off: 84-89% (38-40GFlops) [4] Clarification of all four possible test configs - 8 if you add pinning CPUs or not - might make this a bit clearer? > > Doesn't this make sense? Hyperthreaded cores in Intel procs still > > provide an incomplete set of registers as they're logical processors, > > so I would expect for things to be slower if they're automatically run > > on the SMT cores instead of the physical ones. Since we're talking FP, do HTT 'cores' share an FPU, or have their own? If contended, you'd have to expect worse (at least FP) performance, no? > > Is there a weighting scheme to SCHED_ULE where logical processors > > (like the SMT variety) get a lower score than real processors do, and > > thus get scheduled for less intensive interrupting tasks, or maybe > > just don't get scheduled in high use scenarios like it would if it was > > a physical processor? > > Err... wait. Didn't see that the turbo boost results didn't scale > linearly or align with one another until just a sec ago. Nevermind my > previous comment. Waiting for the fog to lift .. cheers, Ian --0-1044302204-1271305290=:52200--