From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754009AbbICHbm (ORCPT ); Thu, 3 Sep 2015 03:31:42 -0400 Received: from mail-wi0-f174.google.com ([209.85.212.174]:34896 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750749AbbICHbk (ORCPT ); Thu, 3 Sep 2015 03:31:40 -0400 Subject: Re: [PATCH v6 2/3] KVM: dynamic halt_poll_ns adjustment To: David Matlack References: <1441178971-3836-1-git-send-email-wanpeng.li@hotmail.com> <55E74A03.7020508@redhat.com> Cc: Wanpeng Li , kvm list , "linux-kernel@vger.kernel.org" From: Paolo Bonzini Message-ID: <55E7F75B.2030502@redhat.com> Date: Thu, 3 Sep 2015 09:31:39 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/09/2015 21:23, David Matlack wrote: > > I actually wasn't thinking about vcpu->halt_poll_ns though. If > single_task_running() breaks us out of the loop we will "goto out" instead > of scheduling. My suspicion is this will cause us to loop calling > kvm_vcpu_block and starve the waiting task (at least until need_resched()), > which would break the "only hog the cpu when idle" aspect of halt-polling. That's definitely a bug, yes. Paolo