From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH] kvmtool: ARM: timers: add "always-on" property to the device tree Date: Fri, 20 Jun 2014 18:57:58 +0100 Message-ID: <20140620175758.GG30656@arm.com> References: <1403282294-10831-1-git-send-email-marc.zyngier@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "kvmarm@lists.cs.columbia.edu" , "kvm@vger.kernel.org" , Pekka Enberg To: Marc Zyngier Return-path: Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:50404 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752951AbaFTR6C (ORCPT ); Fri, 20 Jun 2014 13:58:02 -0400 Content-Disposition: inline In-Reply-To: <1403282294-10831-1-git-send-email-marc.zyngier@arm.com> Sender: kvm-owner@vger.kernel.org List-ID: On Fri, Jun 20, 2014 at 05:38:14PM +0100, Marc Zyngier wrote: > The new optional property "always-on" indicates that the timers > are, well, always on when used with KVM. > > This allows for substantial performance improvement in the guest > (it switches to NOHZ instead of using a periodic tick per vcpu) > and removes a lot of burden from the host (no need to inject tons > of interrupts with the associated rescheduling overhead). > > Old kernels that don't understand this property will simply ignore it. Acked-by: Will Deacon Will