Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751617AbaJ0KFJ (ORCPT ); Mon, 27 Oct 2014 06:05:09 -0400 Received: from mail-lb0-f182.google.com ([209.85.217.182]:57228 "EHLO mail-lb0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750785AbaJ0KFH (ORCPT ); Mon, 27 Oct 2014 06:05:07 -0400 Message-ID: <1414404302.5564.70.camel@marge.simpson.net> Subject: Re: bisected: futex regression >= 3.14 - was - Slowdown due to threads bouncing between HT cores From: Mike Galbraith To: "Steinar H. Gunderson" Cc: Thomas Gleixner , Linus Torvalds , Linux Kernel Mailing List , Peter Zijlstra Date: Mon, 27 Oct 2014 11:05:02 +0100 In-Reply-To: <20141026141144.GA22911@sesse.net> References: <20141003194428.GA27084@sesse.net> <1412782664.5179.75.camel@marge.simpson.net> <1412791184.5173.11.camel@marge.simpson.net> <1414168721.5308.3.camel@marge.simpson.net> <20141026103918.GA5259@sesse.net> <1414329375.5304.20.camel@marge.simpson.net> <1414331916.5304.23.camel@marge.simpson.net> <20141026141144.GA22911@sesse.net> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2014-10-26 at 15:11 +0100, Steinar H. Gunderson wrote: > I'm maybe a bit surprised nobody else can > reproduce my issue; I tried again this morning, and failed again this morning. >From notes... box = 2 socket, 14 cores/socket +ht, kernel = v3.18-rc2 stockfish 28 threads nps 30511800 time 150120 nps 31337817 time 197553 nps 30675979 time 183005 nps 30706678 time 205037 nps 33389720 time 319808 (note massive runtime (ms) variance) avg 30046381 211104 Adds perturbation source - ring-test -t 56 -w 1 -s 1 -p (pipe ring, work 1ms, sleep 1ms, thread 0-55 pinned to cpu 0-55) One ring did nada, bump to 5 concurrent rings. nps 29443509 time 177969 nps 28713560 time 159663 nps 30628452 time 192714 nps 28834888 time 151611 nps 32611498 time 387760 Hm, still nada, try _10_. nps 29998092 time 164625 nps 31142316 time 178655 Heh, 10 rings of pokers, still nada, try heavier tbench. ... 4 tbench pairs - 4 full cpus worth of competition nps 27157639 time 144184 nps 26511984 time 143998 nps 28408851 time 182903 nps 28501510 time 157897 nps 28357045 time 172855 avg 27787405 160367 (avg runtime drops?.. shrug) Ah, finally a nps delta.. but nothing unexpected. vs zero competition, average nps is 0.924 4 cpus shared ~= stockfish runs on 26 cpus, 26/28 = 0.928 Test session summary: the sun moved westward. -- 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/