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-ia64-devel

Re: [Xen-devel] Question about evtchn_callback reentry

To: "Xu, Anthony" <anthony.xu@xxxxxxxxx>
Subject: Re: [Xen-devel] Question about evtchn_callback reentry
From: Keir Fraser <keir@xxxxxxxxxxxxx>
Date: Mon, 18 Dec 2006 09:31:33 +0000
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, xen-ia64-devel <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Mon, 18 Dec 2006 01:31:08 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <51CFAB8CB6883745AE7B93B3E084EBE207DDA8@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
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: AcciZU0dbGSEqQXwQrycerXX2pFPWAAIgEAJ
Thread-topic: [Xen-devel] Question about evtchn_callback reentry
User-agent: Microsoft-Entourage/11.2.5.060620
On 18/12/06 5:28 am, "Xu, Anthony" <anthony.xu@xxxxxxxxx> wrote:

> If there is no special handling, low privileged interrupt may
> "interrupt" high privileged interrupt.

There's no concept of privilege among event channels. Since Xen simply
allocates ExtInts to vectors in a round-robin manner, there is no meaningful
priority comparsion to be made between vectors anyway.

> BTW,
> I do see evtchn_callback reentry happen on IPF dom0, and that incur
> about 5% performance degradation
> with KB on VTI-domain compared to non_reentry.

KB == Keyboard?!

Reentry is allowed -- it shouldn't happen often unless the ISRs are really
long (bad) or we are hammering the interrupt line for some reason (bad).

 -- Keir


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