[CentOS-virt] poor performance with dom0 on centos7
pasik at iki.fi
Thu Sep 17 07:29:20 UTC 2015
On Wed, Sep 16, 2015 at 09:46:52PM +0200, Christoph wrote:
> Im now pretty sure the problem is the DomU with NFS Server.
> If I write on a NFS share from other Host (bare metal or other vm)
> then I see on my NFS server nearly the whole time 100% io at
> [jbd2/dm-5-8] process...
> If I write on a SMB share (same partition as nfs share) from other
> Host then it is a little bit better but still ever and ever again
> 100% io load
Are you using nfs over UDP or TCP ?
> If I write a 1GB file on the same partition (with nfs/samba share)
> with dd, I dont see the high io load...
> Is there a known problem with nfs/smb shares and/or dm in xen domU's
> on centos 7 as dom0? With centos 6 as dom0 I didnt had the
> (the partition with the shares is a raid5 software partition, soft
> raid is build in dom0 and as a xvd device passed through to the domU
> with the shares)
> could selinux be the problem? I have it in permissive mode on all
> hosts here (dom0 and domU) not disabled...
I don't think.
> Any hints for me?
If you used NFS over UDP, try running it over TCP.
What does 'top' and/or 'iostat -x 1' say during the 'benchmark' ?
> Am 2015-09-01 06:47, schrieb Christoph:
> >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.
> >I have already done what is described on
> >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
> >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)
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