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/
Home Products Support Community News


Re: [Xen-devel] [PATCH] Avoid endless loop for vcpu migration

To: "Juergen Gross" <juergen.gross@xxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Avoid endless loop for vcpu migration
From: "Jan Beulich" <JBeulich@xxxxxxxxxx>
Date: Mon, 14 Mar 2011 15:03:48 +0000
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Mon, 14 Mar 2011 08:03:52 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <9d164ce877a75cab847b.1300113594@nehalem1>
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/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <9d164ce877a75cab847b.1300113594@nehalem1>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
>>> On 14.03.11 at 15:39, Juergen Gross <juergen.gross@xxxxxxxxxxxxxx> wrote:
> On multi-thread multi-core systems an endless loop can occur in vcpu_migrate()
> with credit scheduler. Avoid this loop by changing the interface of pick_cpu
> to indicate a repeated call in this case.

But you're not changing in any way the loop that doesn't get
exited - did you perhaps read my original description as the
pick function itself looping (which - afaict - it doesn't)?

Further, the change still isn't consistent with idle_bias - the
updating ought to happen on the last iteration (if you need
to call the function more than once), not the first one, which
creates a chicken-and-egg problem for you as you will know
it's the last one only when it returned.


Xen-devel mailing list