From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: question about VM kernel parameter idle= Date: Thu, 21 Nov 2013 09:01:39 +0200 Message-ID: <20131121070139.GL19005@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "qemu-devel@nongnu.org" , KVM , Gleb Natapov , Paolo Bonzini , Luonengjun , "Huangweidong (C)" To: "Zhanghaoyu (A)" Return-path: Received: from mx1.redhat.com ([209.132.183.28]:50512 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750860Ab3KUG6a (ORCPT ); Thu, 21 Nov 2013 01:58:30 -0500 Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On Thu, Nov 21, 2013 at 03:45:28AM +0000, Zhanghaoyu (A) wrote: > Hi, all > > What's the difference of the linux guest kernel parameter idle=, especially in performance? > > Taking the performance into account, which one is best? > > In my opinion, if the number of all VMs' vcpus is far more than that of pcpus, e.g. SPECVirt test, idle=halt is better for server's total throughput, > otherwise, e.g. in some CT scenario, the number of total vcpus is not greater than that of pcpus, idle=poll is better for server's total throughput, > because of less latency and VMEXIT. Makes sense overall. > linux-3.9 and above, idle=mwait is not recommended. > > Thanks, > Zhang Haoyu Does it actually have effect? I didn't think it would.