[CentOS-virt] poor performance with dom0 on centos7

[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
> Name                                ID Weight  Cap
> Domain-0                             0   1024    0
> samael                               1    256    0
> satan                                2    512    0
> amon                                 3    256    0
> leviathan                            4    512    0
> 
> 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