[kernel-xen] Centos7 Dom0 IO performance

Glenn Enright glenn at rimuhosting.com
Wed Sep 2 11:13:17 AEST 2015


You may want to look at tweaking which scheduler you are using. Also 
look at the the blkfront drive options eg the command line passed to 
each domU, like extra="elevator=noop xen-blkfront.max=64"

Regards, Glenn
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On 08/31/15 15:51, Christoph Kaminski wrote:
> 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...
>
> Am 2015-08-30 10:21, schrieb Christoph Kaminski:
>> Hi all...
>>
>> 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
>>
>> 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?
>>
>> (I use the xen45 pkgs)
>>
>> TiA
>


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