Pasi Kärkkäinen
2015-Sep-07 19:45 UTC
[CentOS-virt] libvirt, xen PV, qemu-system-i386, root user
On Mon, Sep 07, 2015 at 05:47:39PM +0200, Karel Hendrych wrote:> ... > > changing from: <driver name='file'/> to: <driver name='tap2'/> makes > the domain start without QEMU. > > However I see much better performance with QEMU (close to dom0, > tested using simple dd writes) than with tap2 driver. Is that > expected? >How did you measure it? buffered or direct io? -- Pasi> What's best practise to file based storage on latest CentOS6-xen > (Kernel 3.18.17, Xen 4.4.2-7) > > Are there any guides around running QEMU on CentOS6-xen as non-root user? > > Cheers > -- > Karel > > On 7.9.2015 17:42, Karel Hendrych wrote: > >Hi, spot on! > > > > > >On 6.9.2015 12:56, Pasi K?rkk?inen wrote: > >>On Sun, Sep 06, 2015 at 09:08:50AM +0200, Karel Hendrych wrote: > >>>Hi, after migrating to libvirt/libxl according to: > >>> > >> > >>Hi, > >> > >>>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? > >>> > >> > >>In general qemu is used for the following purposes: > >> > >>- for certain domU disk backend types (image files), and/or if there's > >>no blktap driver in dom0 kernel. > >>- domU graphical console (PVFB) VNC server, if it's enabled for the domU. > >> > >> > >>>-- > >>>Karel Hendrych > >> > >> > >>-- Pasi > >> > >>_______________________________________________ > >>CentOS-virt mailing list > >>CentOS-virt at centos.org > >>https://lists.centos.org/mailman/listinfo/centos-virt > >> > _______________________________________________ > CentOS-virt mailing list > CentOS-virt at centos.org > https://lists.centos.org/mailman/listinfo/centos-virt
Karel Hendrych
2015-Sep-11 23:35 UTC
[CentOS-virt] libvirt, xen PV, qemu-system-i386, root user
Comparing simple dd bs=1M count=10000 on dom0 vs domU. Qemu driver is achieving pretty much the same like dom0. Thanks -- Karel On 7.9.2015 21:45, Pasi K?rkk?inen wrote:> On Mon, Sep 07, 2015 at 05:47:39PM +0200, Karel Hendrych wrote: >> ... >> >> changing from: <driver name='file'/> to: <driver name='tap2'/> makes >> the domain start without QEMU. >> >> However I see much better performance with QEMU (close to dom0, >> tested using simple dd writes) than with tap2 driver. Is that >> expected? >> > > How did you measure it? buffered or direct io? > > > -- Pasi > > >> What's best practise to file based storage on latest CentOS6-xen >> (Kernel 3.18.17, Xen 4.4.2-7) >> >> Are there any guides around running QEMU on CentOS6-xen as non-root user? >> >> Cheers >> -- >> Karel >> >> On 7.9.2015 17:42, Karel Hendrych wrote: >>> Hi, spot on! >>> >>> >>> On 6.9.2015 12:56, Pasi K?rkk?inen wrote: >>>> On Sun, Sep 06, 2015 at 09:08:50AM +0200, Karel Hendrych wrote: >>>>> Hi, after migrating to libvirt/libxl according to: >>>>> >>>> >>>> Hi, >>>> >>>>> 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? >>>>> >>>> >>>> In general qemu is used for the following purposes: >>>> >>>> - for certain domU disk backend types (image files), and/or if there's >>>> no blktap driver in dom0 kernel. >>>> - domU graphical console (PVFB) VNC server, if it's enabled for the domU. >>>> >>>> >>>>> -- >>>>> Karel Hendrych >>>> >>>> >>>> -- Pasi >>>> >>>> _______________________________________________ >>>> CentOS-virt mailing list >>>> CentOS-virt at centos.org >>>> https://lists.centos.org/mailman/listinfo/centos-virt >>>> >> _______________________________________________ >> CentOS-virt mailing list >> CentOS-virt at centos.org >> https://lists.centos.org/mailman/listinfo/centos-virt > _______________________________________________ > CentOS-virt mailing list > CentOS-virt at centos.org > https://lists.centos.org/mailman/listinfo/centos-virt >
Pasi Kärkkäinen
2015-Sep-12 08:51 UTC
[CentOS-virt] libvirt, xen PV, qemu-system-i386, root user
On Sat, Sep 12, 2015 at 01:35:48AM +0200, Karel Hendrych wrote:> Comparing simple dd bs=1M count=10000 on dom0 vs domU. Qemu driver > is achieving pretty much the same like dom0. >So you're measuring buffered speed. Try measuring non-buffered (iflag=direct or oflag=direct, depending if you're reading or writing). -- Pasi> Thanks > -- > Karel > > On 7.9.2015 21:45, Pasi K?rkk?inen wrote: > >On Mon, Sep 07, 2015 at 05:47:39PM +0200, Karel Hendrych wrote: > >>... > >> > >>changing from: <driver name='file'/> to: <driver name='tap2'/> makes > >>the domain start without QEMU. > >> > >>However I see much better performance with QEMU (close to dom0, > >>tested using simple dd writes) than with tap2 driver. Is that > >>expected? > >> > > > >How did you measure it? buffered or direct io? > > > > > >-- Pasi > > > > > >>What's best practise to file based storage on latest CentOS6-xen > >>(Kernel 3.18.17, Xen 4.4.2-7) > >> > >>Are there any guides around running QEMU on CentOS6-xen as non-root user? > >> > >>Cheers > >>-- > >>Karel > >> > >>On 7.9.2015 17:42, Karel Hendrych wrote: > >>>Hi, spot on! > >>> > >>> > >>>On 6.9.2015 12:56, Pasi K?rkk?inen wrote: > >>>>On Sun, Sep 06, 2015 at 09:08:50AM +0200, Karel Hendrych wrote: > >>>>>Hi, after migrating to libvirt/libxl according to: > >>>>> > >>>> > >>>>Hi, > >>>> > >>>>>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? > >>>>> > >>>> > >>>>In general qemu is used for the following purposes: > >>>> > >>>>- for certain domU disk backend types (image files), and/or if there's > >>>>no blktap driver in dom0 kernel. > >>>>- domU graphical console (PVFB) VNC server, if it's enabled for the domU. > >>>> > >>>> > >>>>>-- > >>>>>Karel Hendrych > >>>> > >>>> > >>>>-- Pasi > >>>> > >>>>_______________________________________________ > >>>>CentOS-virt mailing list > >>>>CentOS-virt at centos.org > >>>>https://lists.centos.org/mailman/listinfo/centos-virt > >>>> > >>_______________________________________________ > >>CentOS-virt mailing list > >>CentOS-virt at centos.org > >>https://lists.centos.org/mailman/listinfo/centos-virt > >_______________________________________________ > >CentOS-virt mailing list > >CentOS-virt at centos.org > >https://lists.centos.org/mailman/listinfo/centos-virt > > > _______________________________________________ > CentOS-virt mailing list > CentOS-virt at centos.org > https://lists.centos.org/mailman/listinfo/centos-virt