WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] Question about evtchn_callback reentry

To: Keir Fraser <keir@xxxxxxxxxxxxx>, "Xu, Anthony" <anthony.xu@xxxxxxxxx>
Subject: Re: [Xen-devel] Question about evtchn_callback reentry
From: Keir Fraser <keir@xxxxxxxxxxxxx>
Date: Mon, 18 Dec 2006 13:42:19 +0000
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, xen-ia64-devel <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Mon, 18 Dec 2006 05:42:22 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <C1AC2AE2.63DC%keir@xxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: AcciZU0dbGSEqQXwQrycerXX2pFPWAAIgEAJAAAfzJAAA9BF0QAE0ffJ
Thread-topic: [Xen-devel] Question about evtchn_callback reentry
User-agent: Microsoft-Entourage/11.2.5.060620
On 18/12/06 11:24, "Keir Fraser" <keir@xxxxxxxxxxxxx> wrote:

>> If evtchn_callback reentry is allowed.
>> There are 1024 event channels.
>> In theory, dom0 kernal stack may be overflowed.
>> Is there any mechanism to prevent this?
> 
> When running natively there are over 200 vectors available for allocation to
> interrupt sources. In theory the kernel stack may be overflowed, and there
> is no mechanism in Linux to prevent this.

Okay, so I remember now that of course the APIC divides these into 16
priority levels so that does rather restrict the maximum nesting. I'll be
happy to consider adding prioritisation (or just complete disallow of
nesting) for 3.0.5. But I think you should also work to understand the root
cause of the performance drop on ia64.

 -- Keir


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel