Re: [Xen-devel] Credit scheduler anamoly

[Emmanuel Ackaouy <ack@xxxxxxxxxxxxx>]

Are you running a xen-unstable build containing this changeset
from November 1st?

There was a bug in the cap mechanism -- found by your colleagues
at HP -- when a physical CPU was contended. This changeset seems
to have made things better.

changeset:   12202:9a4274724794
user:        Emmanuel Ackaouy <ack@xxxxxxxxxxxxx>
date:        Wed Nov 01 19:44:34 2006 +0000
summary:     [XEN] Fix credit scheduler cap mechanism not to over park VCPUs


On Tue, Nov 21, 2006 at 04:07:00PM -0600, Padala, Pradeep wrote:
> I sent the following mail without subscribing to the list, and I am not
> sure whether the list accepts mails from non-members. I just subscribed
> and re-sending the mail. I apologize if you receive multiple copies.
> 
> Hi,
> 
> I am using the credit scheduler in the xen-unstable trunk and I am
> trying to set a cap on the container CPU entitlement. I have two VMs and
> two CPUs. The two VMs are restricted to one CPU using the command xm
> vcpu-pin. Now, I want to cap the container CPU consumption say to 4% and
> 26% of the ONE CPU.
> 
> So, I use the following commands.
> 
> xm sched-credit -d 73 -c 4
> xm sched-credit -d 74 -c 26
> 
> When I run Xentop, I see this
> 
> apache.padalap.1 ------         83    7.0 ...
> apache.padalap.2 -----r        154   25.5 ...
> 
> How is this possible when I cap the first VM to 4% ? Am I missing some
> thing ? Does credit scheduler fail to enforce small caps ? Note that I
> haven't changed the weights and they are set to default 256 each.
> 
> Thanks,
> Pradeep
> 
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