From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754308AbdKAGzR convert rfc822-to-8bit (ORCPT ); Wed, 1 Nov 2017 02:55:17 -0400 Received: from mout.gmx.net ([212.227.17.20]:50880 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750925AbdKAGzP (ORCPT ); Wed, 1 Nov 2017 02:55:15 -0400 Message-ID: <1509519263.12290.30.camel@gmx.de> Subject: Re: [PATCH RFC 1/2] sched: Minimize the idle cpu selection race window. From: Mike Galbraith To: Atish Patra , Peter Zijlstra Cc: linux-kernel@vger.kernel.org, joelaf@google.com, brendan.jackman@arm.com, jbacik@fb.com, mingo@redhat.com Date: Wed, 01 Nov 2017 07:54:23 +0100 In-Reply-To: References: <1509427662-25114-1-git-send-email-atish.patra@oracle.com> <1509427662-25114-2-git-send-email-atish.patra@oracle.com> <20171031082009.rxxa57goto6q5xld@hirez.programming.kicks-ass.net> <1509439705.14765.16.camel@gmx.de> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.20.5 Mime-Version: 1.0 Content-Transfer-Encoding: 8BIT X-Provags-ID: V03:K0:4LHV+mp/Fgo+3i0UCKq8S3jybdbGBebUfpQBpkt6x5u2qTkB/fM JrcKh6yXXw2lD9OjnA5KYn1cBmreoZU+3X3YkEXtClLW7wBdO9ZAFKJU5CObyZvX8lWT/AG 1bzSYB6OMnmB7WqK5KGfAZ04nk+9lpcDQSDdEbk8YLwk3mUnmtzkGI5LoyRAOdmIqM0/KS7 jrk5icBOTlWtZWoI9D+pQ== X-UI-Out-Filterresults: notjunk:1;V01:K0:ugGDS/4CrYk=:WlxHtoWs4BU22MkIs4D4C/ 0474yT0HxZlA1aBdFAacNjK6Llmmn2GMM+tLmFWzYW9M3KTUiC5Eprzqmsi1pV3AuBH42lxcg 2sQRIS5nnNooMWqf4knl1QNApjO+Vgz45bKiRQs3FfY1f+QH87X+KpILCTMvKEw0WRwodFWzi WoVILh4Zhni8oF822XK1gZwiQHV2rUiPC8cYHZf32/ZvNBjvejORc6c2jPFm1p83VN3nRC2DN dEOKL7ZV/qYFKfIFxsKaU+bZlY00ExjkgH5rmpLg9OsDFkwh9BCczeIRk1njtIX81m+ZW9nV9 O2YFycKu6gUqZCVj3QAdUPq2VlWJTkn9RUSYmwfX+IGiQJdGDWhiQ9Tq7N7QcTlJDYw+9Iutv +YAQc+c2YrWCGrsh/de5q5SIcX7J1xJZf6MB4N7EDFt/DoRoQOISZHxWxAjQnAO+nq3P4tHQX OWkB6ZvzgtF0XMC9Dg6/sAkNq+sPhl2npBK9NJpdjnnIyzV6vOUUVrC7+nQ8KmHf8GocKExIO Sl/oXHv+PImDSMNOJ6R7pe3goXSJItyotC3aAvh4oX0KXlwi/SsocqLCDUYm9mRUeQFIeMr8Z ahuDzz+N576HYBuU1p//VDxoTj1cGB6NuE6N92ycR59Af5HlFzAV92g9IRWd+p6RVXbZCPcBQ GS9vOo4jwAII6YlSGiwCI44DnRqIoPw4hK9BvBlVAgrpbsy5J6imp4t5Nz3ESZErLufc2UqHe TNTqMat4aoHdQkX6v7EOG5MDxGBErKWVbUfJPj9pGp0eWOFYiTSnK2lNWAAlNIM4n5kOrCvjr C0uD0+LfPDVRZJ9mTK1xjr7CS0xl5Iklv42zi3ncnetoguT5IY= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2017-11-01 at 01:08 -0500, Atish Patra wrote: > > On 10/31/2017 03:48 AM, Mike Galbraith wrote: > > > I played with something ~similar (cmpxchg() idle cpu reservation) > I had an atomic version earlier as well. Peter's suggestion for per cpu > seems to perform slightly better than atomic. Yeah, no doubt about that. > Thus, this patch has the per cpu version. > > a > > while back in the context of schbench, and it did help that, > Do you have the schbench configuration somewhere that I can test? I > tried various configurations but did not > see any improvement or regression. No, as noted, I didn't save anything.  I watched and fiddled with several configurations on various sized boxen, doing this/that on top of the reservation thing to try to improve the "it's 100% about perfect spread" schbench, but didn't like the pricetag, so tossed the lot over my shoulder and walked away. -Mike