* Richard W.M. Jones <rjones@redhat.com> [2010-09-06 17:59]:
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.
xentop is *magnitudes* faster than virt-top, really. "xm list" takes ages whereas "xenstore-list /local/domain" is quite fast, also "xenstore-list /local/domain \ | while read domid; do \ xenstore-read /local/domain/${domid}/name; done" (to get even the domain's name). Cheers, Wolfram