[libvirt-users] How to lookup the driver instance through virConnectPtr pointer

Dennis Chen dennis.chen at tnsoft.com.cn
Thu Nov 22 09:34:46 UTC 2012

On 11/21/2012 10:00 PM, Eric Blake wrote:
> On 11/21/2012 02:42 AM, Dennis Chen wrote:
> [I will note that today's email chain should have been as a new thread,
> rather than in-reply to a thread from July - changing subject lines and
> deleting all previous content still doesn't stop your mailer from using
> In-Reply-To headers]
>> Yeah, I know. So the email is try to get to know how to use cgroup to
>> configure the cpu bandwidth of a specific VM, I am writing a separate
>> project to control the cfs bandwidth of a VM specified, not taking use
>> of the virsh shell.
> You do this by modifying the domain XML:
> http://libvirt.org/formatdomain.html#elementsCPUTuning
> documents the<cputune>  element, which includes the shares, period, and
> quota tunables that map into the cpu bandwidth cgroup tunables.  So,
> rather than directly modifying cgroup, you should instead be modifying
> this portion of the XML.
> Furthermore, if your domain is already running, then you can hotplug the
> tuning via the virDomainGetSchedulerParametersFlags() and
> virDomainSetSchedulerParametersFlags() API, with parameter names such as
> VIR_DOMAIN_SCEDULER_VCPU_PERIOD which maps back to the<period>
> sub-element of the<cputune>  domain XML.  These APIs are already exposed
> via the 'virsh schedinfo' command.

Hi Eric,

Those APIs are really the one I needed, thanks very much for the help. After a rough test, it works!

though, I can't find the VIR_DOMAIN_SCEDULER_VCPU_PERIOD macro in the libvirt source code...


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