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Re: [libvirt] virt-top version bump in EPEL5



On Mon, Sep 06, 2010 at 05:46:03PM +0200, Wolfram Schlich wrote:
> * Richard W.M. Jones <rjones redhat com> [2010-09-06 17:23]:
> > On Mon, Sep 06, 2010 at 05:06:55PM +0200, Wolfram Schlich wrote:
> > > We are experiencing a problem with virt-top on our RHEL5 virthosts.
> > > 
> > > On a heavily loaded virthost, virt-top is damn slow -- it takes 4-5s
> > > to update and imposes a noticeable load on the dom0 as well
> > > (xenstored shows up in top eating all CPU for some seconds).
> > > xentop seems to impose *much* less load on the dom0.
> > > Is there something I can do about it?
> > >
> > > Another problem: 0.3.3.1 shows RDRQ/WRRQ/RXBY/TXBY after some seconds
> > > whereas 1.0.4 does not...?
> > 
> > I bet both of these will be libvirt issues.
> > 
> > Try running:
> > 
> > virsh list --all
> 
> Takes around 2-4s depending on dom0 load.

CC-ing to libvir-list.  There may be a better way now for virt-top to
get the list of domains, but if 'virsh list --all' is also slow, then
it's probably a generic libvirt problem.

> > virsh domblkstat DomainName hda
> 
> s/hda/xvda/ I guess :)
> This one is quite fast, below 0.2s.
> 
> > virsh domifstat DomainName vnet0
> 
> This takes around 0.1s most of the time, but sometimes around 1.0s.
> 
> > etc.
> > 
> > If those commands (done in a suitable loop) also cause load on the
> > dom0, and if domblkstat/domifstat don't show stats, then it's down to
> > libvirt.
> > 
> > virt-top is a simple little program that just exercises those libvirt
> > APIs ...
> 
> Hmm :/ So I guess we're better off with xentop...

We should be able to have performance very close to xentop.  After
all, libvirt makes exactly the same direct hypervisor calls.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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