Re: [Xen-users] poor IO performance with dom0 on centos7

[Roger Pau Monnà <roger.pau@xxxxxxxxxx>]

Hello,

El 01/09/15 a les 6.11, Christoph ha escrit:
> Hi All
> 
> 
> 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.

Is the performance in Dom0 as expected?

> 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?

Can you paste the DomU configuration files?

Are both network and disk slow, or only one of them? I would recommend
using fio/iperf in order to figure out which one is the bottleneck, or
if both are.

> 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...

Not sure about that, I've never used selinux and I don't know which
impact it has on performance.

Roger.

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