From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jan Beulich" Subject: Re: increase evtchn limits Date: Fri, 21 May 2010 09:14:01 +0100 Message-ID: <4BF64EDA020000780005E1FE@vpn.id2.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: keir.fraser@eu.citrix.com, mukesh.rathor@oracle.com Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org >>> Keir Fraser 05/21/10 9:06 AM >>> >How many CPUs do you have to bring up? How many event channels are we >squandering per CPU in PV Linux right now (can you enumerate them)? There are 5 event channels per CPU (timer, reschedule IPI, SMP call = function IPI, SMP call function single IPI, and spinlock wakeup IPI). While 4096 may seem plenty, I don't think it really is: With larger = systems you not only have more CPUs, but you also generally have more = devices (with e.g. MSI-X ones possibly requiring quite a number of event = channels per device) plus you also expect to be able to run more guests, = which in turn requires more event channels in Dom0. So I agree with Mukesh = that we ought to find a reasonable way to overcome this limit. Jan