From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: [PATCH 0/4] Really lazy fpu Date: Wed, 16 Jun 2010 00:32:01 -0700 Message-ID: <4C187DF1.9030007@zytor.com> References: <1276441427-31514-1-git-send-email-avi@redhat.com> <4C187C22.2080505@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Ingo Molnar , kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Avi Kivity Return-path: Received: from terminus.zytor.com ([198.137.202.10]:47032 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751094Ab0FPHc3 (ORCPT ); Wed, 16 Jun 2010 03:32:29 -0400 In-Reply-To: <4C187C22.2080505@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 06/16/2010 12:24 AM, Avi Kivity wrote: > > Ingo, Peter, any feedback on this? > Conceptually, this makes sense to me. However, I have a concern what happens when a task is scheduled on another CPU, while its FPU state is still in registers in the original CPU. That would seem to require expensive IPIs to spill the state in order for the rescheduling to proceed, and this could really damage performance. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.