From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754288AbbE1Lzw (ORCPT ); Thu, 28 May 2015 07:55:52 -0400 Received: from e28smtp09.in.ibm.com ([122.248.162.9]:35327 "EHLO e28smtp09.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753540AbbE1Lzo (ORCPT ); Thu, 28 May 2015 07:55:44 -0400 Date: Thu, 28 May 2015 17:25:37 +0530 From: Srikar Dronamraju To: Josef Bacik Cc: riel@redhat.com, mingo@redhat.com, peterz@infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RESEND] sched: prefer an idle cpu vs an idle sibling for BALANCE_WAKE Message-ID: <20150528115537.GA25636@linux.vnet.ibm.com> Reply-To: Srikar Dronamraju References: <1432761736-22093-1-git-send-email-jbacik@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1432761736-22093-1-git-send-email-jbacik@fb.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15052811-0033-0000-0000-00000600ACEB Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > At Facebook we have a pretty heavily multi-threaded application that is > sensitive to latency. We have been pulling forward the old SD_WAKE_IDLE code > because it gives us a pretty significant performance gain (like 20%). It turns > out this is because there are cases where the scheduler puts our task on a busy > CPU when there are idle CPU's in the system. We verify this by reading the > cpu_delay_req_avg_us from the scheduler netlink stuff. With our crappy patch we > get much lower numbers vs baseline. > Was this application run under cpu cgroup. Because we were seeing bursty workloads exhibiting this behaviour esp when run under cpu cgroups. http://mid.gmane.org/53A11A89.5000602@linux.vnet.ibm.com -- Thansk and Regards Srikar