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1612 discussions

poor performance with dom0 on centos7
by Christoph 17 Sep '15

17 Sep '15

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

2 3

adding xen support to grub2 got segfault running grub2-mkimage
by Mark Pryor 17 Sep '15

17 Sep '15

There is some interest lately in making a self-contained grub2 boot image - call it pvgrub2, used for booting paravirtual domU in xen where a grub2 config is installed. First attempt------------------ I first tried using the grub2*.src.rpm from the C7 vault. I configured as shown belowhttps://blog.xenproject.org/2015/01/07/using-grub-2-as-a-bootloader-fo… for headers, I used xen-devel, xen-libs, xen-licenses from a recent build I didhttp://107.185.144.55/xen/cent7/dom0/RPMS/stable-4.5/mock/ this gave a segfault from grub2-mkimage with a cmdline like/usr/bin/grub2-mkimage -O x86_64-xen -C auto -d /usr/lib/grub/x86_64-xen -c ./grub-bootstrap.cfg -m ./memdisk.tar -o ./grub2-x86_64-xen.bin -v ext2 fat file font fshelp gzio halt hashsum help legacycfg linux loadenv loopback part_dvh part_gpt part_msdos part_plan part_sun xfs xnu_uuid xnu_uuid_test xzio the image would finish if I cut down the module list to about 8 or less modules. This is not enough for a useful image . Second Attempt----------------In the same build env, I started with the git clone (see link). Now when running grub-mkimage I included all the modules in/usr/lib/grub/x86_64-xen/ and the image formed without error and works as expected as a xen bootloader. The only difference in the two builds is the size of grubX-mkimage: one is stripped and the other not. Using the official grub2 C7 packages failed and a rogue build from git worked. regards,PryMar56

2 2

FYI: Some changes to libguestfs / libguestfs-winsupport / virt-v2v / virt-p2v in RHEL 7.2
by Richard W.M. Jones 16 Sep '15

16 Sep '15

libguestfs is a set of tools for reading and modifying disk images and virtual machines. virt-v2v and virt-p2v are tools for converting guests from foreign hypervisors (especially VMware, Xen), or physical machines, to run on KVM (eg. virt-manager, OpenStack/RHOS or oVirt/RHEV). This is just a heads-up about some changes to the way libguestfs and related packages will be packaged in RHEL 7.2. Previously (<= 7.1): - libguestfs required qemu-kvm-rhev (qemu-kvm-ev in CentOS). - libguestfs-winsupport was in a separate RHEL channel. - libguestfs-winsupport had file conflicts with ntfs-3g. - virt-v2v was not shipped in RHEL 7.1. - There were missing BuildRequires. Starting with RHEL 7.2: - libguestfs requires qemu-kvm. (You can still use qemu-kvm-ev if you want). - There is an upgraded qemu-kvm package that contains the extra features from qemu-kvm-ev that libguestfs needed. - libguestfs-winsupport will be shipped in the base RHEL Server channel, as an ordinary package. - libguestfs-winsupport won't conflict with any EPEL packages. - virt-v2v is built as a binary sub-package of libguestfs, and shipped in the base RHEL Server channel. - There should be no missing BuildRequires this time. Hopefully this is a simplification, and will make everyone's job easier. If there's any fall-out from these changes that affects CentOS, please let me know - best to CC me on any emails. - - - Now for something that is -- unfortunately -- still complicated: virt-p2v is a CD/ISO that we build to allow conversions of physical machines to KVM. You have to boot the physical machine with the CD. For this reason the virt-p2v ISO that we give to RHEL customers contains a bootable RHEL distro. In RHEL we build this using an (IMHO over-complicated) method starting with a kickstart, building an ISO, and then wrapping the ISO in an RPM. If CentOS has a way to ship ISOs, then it's likely better for CentOS just to build the ISO and stop there. To get the kickstart, run: $ virt-p2v-make-kickstart -o p2v.ks http://centos.org/path/to/7.2/repo Further instructions here: http://libguestfs.org/virt-p2v-make-kickstart.1.html Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-builder quickly builds VMs from scratch http://libguestfs.org/virt-builder.1.html

1 0

Using STP in kvm bridges
by C.L. Martinez 16 Sep '15

16 Sep '15

Hi all, Reading docs about using bridges in a KVM environment, I have a doubt about activating STP or not in a KVM host. What advantages and disadvantages have?? If I will want to install some kvm guests that use multicast address for certain services, is it recommended to enable STP? Thanks.

3 6

libvirt, xen PV, qemu-system-i386, root user
by Karel Hendrych 14 Sep '15

14 Sep '15

Hi, after migrating to libvirt/libxl according to: https://wiki.centos.org/HowTos/Xen/Xen4QuickStart/Xen4Libvirt I've noticed that my Xen PV domains are being launched by qemu-system-i386 running under root privileges. I am wondering why is this? Previously no qemu process was used. If qemu is needed for some reason, are there any guidelines for non-root operation? Thanks -- Karel Hendrych

3 8

Report on Xen-4.6rc2 from virt7-xen-46-candidate
by T.Weyergraf 10 Sep '15

10 Sep '15

Hi I gave the new Xen-4.6rc2 a spin on a CentOS 7 virtualisation guest (nested-xen). I haven't yet started testing guests, but rather looked at the install itself. One issue, I found, was with xenstored.service and the corresponding unit-file: [root@xencen7ws ~]# systemctl status xenstored xenstored.service - The Xen xenstore Loaded: loaded (/usr/lib/systemd/system/xenstored.service; disabled) Active: active (running) since Tue 2015-09-08 23:13:43 CEST; 13min ago Process: 757 ExecStartPre=/bin/mkdir -p /var/run/xen (code=exited, status=0/SUCCESS) Process: 753 ExecStartPre=/bin/rm -f /var/lib/xenstored/tdb* (code=exited, status=0/SUCCESS) Process: 740 ExecStartPre=/bin/grep -q control_d /proc/xen/capabilities (code=exited, status=0/SUCCESS) Main PID: 760 (xenstored) CGroup: /system.slice/xenstored.service └─760 /usr/sbin/xenstored Sep 08 23:13:43 xencen7ws.virtfinity.local xenstored[760]: TDB: tdb_open_ex: could not open file /var/lib/xenstored/tdb: No such file or directory Sep 08 23:13:43 xencen7ws.virtfinity.local xenstored[760]: Checking store ... Sep 08 23:13:43 xencen7ws.virtfinity.local xenstored[760]: Checking store complete. Sep 08 23:13:43 xencen7ws.virtfinity.local xenstored[760]: xenstored is ready Sep 08 23:13:43 xencen7ws.virtfinity.local systemd[1]: Started The Xen xenstore. As you can see, xenstored.service is running, but disabled by the package installation. This is, because xenstored.service apparently got overseen in the source-rpm's spec-file's post runtime/preun runtime. See diff [1] for details. Also, I think xenstored should write a pidfile. You might consider adding to /usr/lib/systemd/system/xenstored.service: PIDFile=/var/run/xenstored.pid and change ExecStart=/usr/sbin/xenstored to ExecStart=/usr/sbin/xenstored --pid-file /var/run/xenstored.pid $XENSTORED_ARGS Hope this helps, this is just a quick start. I'll continue checking and reporting during the next days. Regards, Thomas [1] diff -u rpmbuild-xen-4.6rc2x-3.el7-org/SPECS/xen.spec rpmbuild-xen-4.6rc2x-3.el7/SPECS/xen.spec --- rpmbuild-xen-4.6rc2x-3.el7-org/SPECS/xen.spec 2015-09-08 18:47:00.000000000 +0200 +++ rpmbuild-xen-4.6rc2x-3.el7/SPECS/xen.spec 2015-09-09 00:06:27.558344410 +0200 @@ -403,6 +403,7 @@ /bin/systemctl enable xen-qemu-dom0-disk-backend.service /bin/systemctl enable xen-init-dom0.service /bin/systemctl enable xenconsoled.service + /bin/systemctl enable xenstored.service # /bin/systemctl enable xendomains.service %endif @@ -422,6 +423,7 @@ /bin/systemctl disable xen-init-dom0.service /bin/systemctl disable xen-qemu-dom0-disk-backend.service /bin/systemctl disable xenconsoled.service + /bin/systemctl disable xenstored.service # /bin/systemctl disable xendomains.service %endif fi

3 5

Xen specfile git repos
by George Dunlap 10 Sep '15

10 Sep '15

There was some discussion about the lack of visibility of the Xen4CentOS development process. The Xen spec files and supporting patches are kept in a git tree. I've pushed copies of these trees here: https://github.com/gwd/sig-virt-xen xen-44 is the branch for Xen 4.4 development, and xen-46 is the branch for Xen 4.6 development. As is normal, these repos do not contain many of the binary tarballs required to build. The best way to get these is to download a recent srpm (from http://cbs.centos.org/repos/virt7-xen-46-testing/source/SRPMS/ -- replacing virt6 with virt7 or 44 with 46 as appropriate). The patches to the xen hypervisor are in a rather unusual format: a git "am". This makes it *much* easier to rebase and manipulate the queue if you're familiar with git; but it does add a bit to get familiar with. To manipulate the am patchqueue (using 4.4.3 as an example): 1. Check out a git repo and make a branch based on the baseline version $ git checkout -b centos/pq/4.4.3 RELEASE-4.4.3 2. Import SOURCES/xen-queue.am $ git am ${path-to-package-repo}/SOURCES/xen-queue.am OR using stackgit: $ stg init $ stg import -M ${path-to-package-repo}/SOURCES/xen-queue.am 3. Manipulate the patchqueue using normal git (or stackgit) commands 4. Export the queue again: git format-patch --stdout -N RELEASE-4.4.3 > ${path-to-package-repo}/SOURCES/xen-queue.am -George

1 1

CentOS 7 Xen 4.6-rc2+ packages available for in virt7-xen-46-testing
by George Dunlap 09 Sep '15

09 Sep '15

OK, last but not least -- Xen 4.6-rc2 packages available for CentOS 7! The Xen continuous testing infrastructure has improved dramatically over the last few years, so rc2 should already be quite stable. Please test. In particular the most recent build moves packages over from using the chkconfig compat layer to using the properly integrated systemd scripts. As usual: rpm -ivh http://cbs.centos.org/repos/virt7-xen-46-testing/x86_64/os/Packages/centos-… This will set up yum repositories for both the eventual release repositories (enabled by default), and the community build system repositories (disabled by default). At the moment, all packages will be stored in the virt-xen-44-testing repository. You can either enable this by default by editing /etc/yum.repos.d/VirtSIG-Xen.repo, or by adding "--enablerepo=virt-xen-44-testing". If you want, you can edit defaults /etc/sysconfig/xen-kernel Next, run 'yum update' to get the new kernel: yum --enablerepo=virt-xen-44-testing update kernel Now install xen: yum --enablerepo=virt-xen-44-testing install xen This should grab both xen and the updated kernel package. It should also automatically: * Add default commandline parameters for Xen and Linux when booting under Xen * Arrange for xen to come up first in the grub * Set the default boot entry to Xen. That's it! Reboot and you should be good to go. libvirt packages have not been built yet. Please report any problems or feedback to this list. -George

1 0

Xen 4.4.3 packages available in virt6-xen-44-testing
by George Dunlap 09 Sep '15

09 Sep '15

So first of all, if you've used the CBS before, please note the name change -- it's no longer virt6-testing, but virt6-xen-44-testing. Easiest way to install: rpm -ivh http://cbs.centos.org/repos/virt6-xen-44-testing/x86_64/os/Packages/centos-… This will set up yum repositories for both the eventual release repositories (enabled by default), and the community build system repositories (disabled by default). At the moment, all packages will be stored in the virt-xen-44-testing repository. You can either enable this by default by editing /etc/yum.repos.d/VirtSIG-Xen.repo, or by adding "--enablerepo=virt-xen-44-testing". If you want, you can edit defaults /etc/sysconfig/xen-kernel Next, run 'yum update' to get the new kernel: yum --enablerepo=virt-xen-44-testing update kernel Now install xen: yum --enablerepo=virt-xen-44-testing install xen This should grab both xen and the updated kernel package. It should also automatically: * Add default commandline parameters for Xen and Linux when booting under Xen * Arrange for xen to come up first in the grub * Set the default boot entry to Xen. That's it! Reboot and you should be good to go. Libvirt packages haven't been rebuilt -- not sure if they work or not. If they don't, let me know and I'll re-submit them.. Please report any problems or feedback to this list. -George

2 5

Beta CentOS 7 Xen packages available
by George Dunlap 08 Sep '15

08 Sep '15

At long last, I'd like to announce beta packages for CentOS 7, available from the community build system. Start by installing the centos-release-xen: rpm -ivh http://cbs.centos.org/repos/virt7-xen-44-testing/x86_64/os/Packages/centos-… This will set up yum repositories for both the eventual release repositories (enabled by default), and the community build system repositories (disabled by default). At the moment, all packages will be stored in the virt-xen-44-testing repository. You can either enable this by default by editing /etc/yum.repos.d/VirtSIG-Xen.repo, or by adding "--enablerepo=virt-xen-44-testing". If you want, you can edit defaults /etc/sysconfig/xen-kernel Next, run 'yum update' to get the new kernel: yum --enablerepo=virt-xen-44-testing update kernel Now install xen: yum --enablerepo=virt-xen-44-testing install xen This should grab both xen and the updated kernel package. It should also automatically: * Add default commandline parameters for Xen and Linux when booting under Xen * Arrange for xen to come up first in the grub * Set the default boot entry to Xen. That's it! Reboot and you should be good to go. Libvirt packages aren't available yet but should be on the way soon (I'll announce them here.) Please report any problems or feedback to this list. -George

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