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 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... Any hints for me? 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) -- ------ Greetz