On Wed, Sep 16, 2015 at 09:46:52PM +0200, Christoph wrote:
Hi
Hi,
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 problem... (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' ?
-- Pasi
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 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)
--
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