Re: [CentOS-virt] poor performance with dom0 on centos7

2015-09-02 Thread Pasi Kärkkäinen 
On Tue, Sep 01, 2015 at 06:47:18AM +0200, Christoph wrote:
> Hi All
> 

Hello,

> it is possible to tune dom0/domU for better IO/network performance?
> Since I have changed to Cenots7 dom0, I have a really poor IO
> performance inside a PV VM.
> 
> I have already done what is described on
> http://wiki.xenproject.org/wiki/Tuning_Xen_for_Performance
> It is better now but still significantly worse than with centos6 dom0
> 
> my settings:
> 
> xen parameter: dom0_mem=1024M cpufreq=xen dom0_max_vcpus=2
> dom0_vcpus_pin
> 
> xl sched-credit
> Cpupool Pool-0: tslice=30ms ratelimit=1000us
> NameID Weight  Cap
> Domain-0 0   10240
> samael   12560
> satan25120
> amon 32560
> leviathan45120
> 
> echo 1048576 > /proc/sys/net/ipv4/tcp_limit_output_bytes on dom0
> 
> the both domU's satan and leviathan are very IO performance oriented
> (NFS server and downloading vm)
> 
> Is there something more what I can do or try?
> 
> could it be a selinux issue? I have it in permissive mode there, not
> disabled. But permissive means only to collect the info not enforcing
> the rules...
> 
> (I use the xen45 pkgs)
> 

You forgot to mention the most important thing.. what kind of performance 
numbers are you seeing? What are you expecting? 


Thanks,

-- Pasi

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[CentOS-virt] Assigning a PCI sound device to a VM

2015-09-02 Thread Robert Nichols 

I have a PCI sound card that I would like to assign to a VM, but
when I try to do so the VM fails to start and displays this message:

Error starting domain: Unable to read from monitor: Connection reset by peer

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 44, in 
cb_wrapper

callback(asyncjob, *args, **kwargs)
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 65, in tmpcb
callback(*args, **kwargs)
  File "/usr/share/virt-manager/virtManager/domain.py", line 1125, in 
startup

self._backend.create()
  File "/usr/lib64/python2.6/site-packages/libvirt.py", line 686, in create
if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
libvirtError: Unable to read from monitor: Connection reset by peer

The XML generated by virt-manager for the device is


  

  
  function='0x0'/>



The sound card is an Asus Xonar DGX PCIe 5.1, and identifies itself
as "07:04.0 Multimedia audio controller: C-Media Electronics Inc CMI8788 
[Oxygen HD Audio]".


I see the same problem if I try to assign the motherboard's Intel
Xeon E3-1200 HD Audio Controller to the VM.  Both of these devices
are supported by the host kernel (3.18.17-13.el6.x86_64).

I have no problem assigning a USB sound device, but those have very
limited capability.

--
Bob Nichols "NOSPAM" is really part of my email address.
Do NOT delete it.

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