From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752629AbaHCRaf (ORCPT ); Sun, 3 Aug 2014 13:30:35 -0400 Received: from one.firstfloor.org ([193.170.194.197]:33233 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751769AbaHCRae (ORCPT ); Sun, 3 Aug 2014 13:30:34 -0400 Date: Sun, 3 Aug 2014 19:30:31 +0200 From: Andi Kleen To: Sergey Oboguev Cc: Mike Galbraith , Andi Kleen , linux-kernel@vger.kernel.org, khalid.aziz@oracle.com Subject: Re: [PATCH RFC] sched: deferred set priority (dprio) Message-ID: <20140803173031.GQ18735@two.firstfloor.org> References: <8738dm9t4z.fsf@tassilo.jf.intel.com> <1406532289.5133.223.camel@marge.simpson.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > (One example might be virtual machine that runs guest operating system that is > not paravirtualized or can be paravirtualized only to a limited extent. The VM > might guess that preemption of VCPU thread that is processing events such as > IPI interrupts, clock interrupts or certain device interrupts is likely to > cause overall performance degradation due to other VCPUs spinning for an IPI > response or spinning waiting for a spinlock, and thought the general kinds of > these dependencies may be foreseen, but actual dependency chains between VCPUs > cannot be established at run time.) PAUSE loop exiting (PLE) can handle it in limited fashion on VMs even without paravirtualization. -Andi -- ak@linux.intel.com -- Speaking for myself only.