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] unnecessary VCPU migration happens again

To: "Emmanuel Ackaouy" <ack@xxxxxxxxxxxxx>
Subject: RE: [Xen-devel] unnecessary VCPU migration happens again
From: "Xu, Anthony" <anthony.xu@xxxxxxxxx>
Date: Fri, 22 Dec 2006 10:26:12 +0800
Cc: "Petersson, Mats" <Mats.Petersson@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, xen-ia64-devel <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Thu, 21 Dec 2006 18:26:27 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
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: AcclHEcpp2gyphXkRtSn398V9DANLwAUzD5w
Thread-topic: [Xen-devel] unnecessary VCPU migration happens again
Hi Emmanuel,

Thanks for your quick response.
I'm not familiar with scheduler, I'll study it. :-)

I put comments below, maybe it's not right. :-)

Emmanuel Ackaouy write on 2006年12月22日 0:23:
> Hi Anthony.
> Based on the number of "ticks" on CPU0 that occurred between the
> two stat dumps, over 16 minutes elapsed during that time.
> During that time, 364 regular migrations occurred. These are
> migrations that happen when an idle CPU finds a runnable VCPU queued
> elsewhere 
> on the system.

>From the point of user of credit scheduler, it may be not regular migrations.
Because there are 4 CPU, and there are only 3 VCPU,

It would be unlikely that an idle CPU finds a runnable VCPU queued elsewhere 
 on the system.

> Also during that time, 530 multi-core load balancing migrations
> happened.
> That's about one such migration every 1.86 seconds. I'm somewhat
> surprised
> that this costs 5% in performance of your benchmark. That said, the
> point
> of this code is to balance a partially idle system and not to shuffle
> things
> around too much so I'm happy to smooth the algorithm further to reduce
> the
> number of these migrations.

I'm interested about this.
I'll investigate this.

> I'll send another patch shortly.
Thanks again.

> On Dec 20, 2006, at 4:26, Xu, Anthony wrote:
>> Before running KB
>> (XEN)   migrate_queued                 = 169
>> (XEN)   migrate_running                = 213
>> (XEN) CPU[00]  tick=117181, sort=12233, sibling=0x1, core=0x5
>> After running KB
>> (XEN)   migrate_queued                 = 533
>> (XEN)   migrate_running                = 743
>> (XEN) CPU[00]  tick=215790, sort=42999, sibling=0x1, core=0x5

Xen-devel mailing list