From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755945Ab1JCNOX (ORCPT ); Mon, 3 Oct 2011 09:14:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44853 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754431Ab1JCNOS (ORCPT ); Mon, 3 Oct 2011 09:14:18 -0400 Date: Mon, 3 Oct 2011 09:13:28 -0400 From: Don Zickus To: Avi Kivity Cc: Robert Richter , "x86@kernel.org" , Andi Kleen , Peter Zijlstra , "ying.huang@intel.com" , LKML , "paulmck@linux.vnet.ibm.com" , "jeremy@goop.org" Subject: Re: [V6][PATCH 4/6] x86, nmi: add in logic to handle multiple events and unknown NMIs Message-ID: <20111003131328.GW5795@redhat.com> References: <1316805435-14832-1-git-send-email-dzickus@redhat.com> <1316805435-14832-5-git-send-email-dzickus@redhat.com> <20110928103140.GD6063@erda.amd.com> <20110928123720.GL5795@redhat.com> <4E8837D4.5040607@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4E8837D4.5040607@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Oct 02, 2011 at 12:07:16PM +0200, Avi Kivity wrote: > >Right. Avi, Jeremy what was your objection that needed this optimization > >in the first place? > > > > First, iterating over all NMI sources is going to be slow, and a lot > more so in a guest. This reduces the performance of perf. I understand and agree. The only positive I can offer is most machines will most likely only have two NMI handlers registered: perf and arch_backtrace. So any slowness should be minimal. We might even be able to code up arch_backtrace to register its NMI handler when it is called to minimize the the number of NMI sources even more. Cheers, Don > > Second, I wanted to use NMIs as a way of waking up a vcpu sleeping > with interrupts disabled (in the context of Jeremy's paravirt > spinlock patches). Looks like we'll have to use paravirtualization > for that. > > -- > error compiling committee.c: too many arguments to function >