[kvm-devel] (long) kvm and virt-manager not ready for daily usage
hi, in the last 2 weeks we play a lot with our new server which we but to a our virtual server for the development and collect some very subjective experience. we use kvm and virt-manager, but sometimes i'm not really sure about the whether it's kvm or virt-manager problem so i collect them together. our system: MB: Intel S3000AHV CPU: Intel Core 2 Quad CPU Q6600 @ 2.40GHz RAM: 8GB CentOS 5 x86-64 host system with: kernel-2.6.18-8.1.8.el5 kmod-kvm-35-1.2.6.18_8.1.8.el5 kvm-35-1 libvirt-0.3.2-2 libvirt-python-0.3.2-2 python-virtinst-0.300.0-1 virt-manager-0.5.0-1 virt-top-0.3.2.5-1 virt-viewer-0.0.2-1 kvm is not ready for production use for many reason: it can't reboot which imho a very basic feature, what's more can't even shutdown/poweroff. the centos i386 guest are not able to shutdown on the x86_64 host (strange the x86_64 centos and the i586 mandrake-9 are able to shutdown) or what's seems to be more likely it's a random think. can't give 2GB ram to any guests not even 2, but 1. is ok. what's more i've to discover this in the hard way virt-manager gives some strange error message (anyway none of the virt-manager's error message are useful, just strange stack trace without any kind of useful info). the host see as i've 4 cpu. i've got a change to gives more cpu to the guest, what's more they starts, but after a few minutes running the system crash. not just the guest os but the host os crash without any kind of info, log or any useful info what was the cause of it, but hard reset helps:-((( first of all it's serious problem, even if it's a known bug and documented somewhere (but there is not any kind of docs about neither kvm nor virt-manager/libvirt and what i can find that very limited), since all of the new hvm cpu (which is required for kvm) has more core, so the guest can't use the real power of the cpu this means i've to put a lots of guests with one virtual cpu to the host or currently can't exploit these cpus. libvirt not start the guest when the host started, not saved the state of the guests when stopped, when restarted all guest get into shutdown state. may be it's just libvirt but, but if kvm not able to save it's guest's state that it's a real pain. this behavior not acceptable in a real environment. in virt-manager can't modify virtual cpu number of the guests (virt-manager crash with another unusable stacks trace). it i modify the xml config file by hand i've to restart libvirt in order to read it. even if i just modify one guest's config, but as if i restart libvirtd the all other guest will be killed it's another nice feature. from vit-manager i can't assign swap partitions (and any other device to the guests) during guest creation. i precreate lvm partition on the host for root and swap to all of our guests (about 10) but it's a real pain to reload libvirtd (which kills all guests) to add a new disk to the guest which can be used as a swap or other partition. what's more it'd be useful to add swap partition during install. the same thing apply to cdrom too. if i made a mistake in the libvirtd xml config file, then i don't get any kind of error message just libvirt don't start the given guest. no error message service seems to start without error and don't know what was the reason that the guest not start (sometimes because syntactic error in the config file, sometimes kvm/qemu not support it eg more then 2gb mem). there are unwritten unix/linux tradition eg if there are error during a service startup report it some log file. if a service can't start without error then it not start at all eg. if i've apache with 5 virtual host but one of it's config has error then the whole httpd not started. it'd have to be the same with libvirt too. libvirt config file has all the features as qemu command line (if not it can't be used by advanced users)? but i don't know since there is not a reference docs for the config file. there is not a detailed reference docs about libvirtd config (and at the same time the gui not contains all the settings). for the the xml format is a bit redundant eg. "source dev", "target dev" why not just source and target, inside interface type='bridge' 'source bridge' why not just source (i've to modify two place when i'd like to switch from network to bride. ok these are just small cosmetic thing just mention. when create a new guest in virt-manager and reach the last page and press finish then most of the time (2 times from 3) i've got an error something like "can't connect to qemu" after i press ok and press again finish then it's able to create the new host (so always have to retry it). in virt-manager when a guest is shutdown and double-click on the guest and try to start it it's not possible. you've to select the guest in the main windows, right-click and start it. the new vnc based console is very unstable or just virt-manager not able to connect it. many times i double click on a guest in virt-manager i got the window can't connect to console while
Re: [kvm-devel] (long) kvm and virt-manager not ready for daily usage
Farkas Levente wrote: > hi, > in the last 2 weeks we play a lot with our new server which we but to a > our virtual server for the development and collect some very subjective > experience. we use kvm and virt-manager, but sometimes i'm not really > sure about the whether it's kvm or virt-manager problem so i collect > them together. our system: > thansk! > MB: Intel S3000AHV > CPU: Intel Core 2 Quad CPU Q6600 @ 2.40GHz > RAM: 8GB > CentOS 5 x86-64 host system with: > kernel-2.6.18-8.1.8.el5 > kmod-kvm-35-1.2.6.18_8.1.8.el5 > kvm-35-1 > libvirt-0.3.2-2 > libvirt-python-0.3.2-2 > python-virtinst-0.300.0-1 > virt-manager-0.5.0-1 > virt-top-0.3.2.5-1 > virt-viewer-0.0.2-1 > > kvm is not ready for production use for many reason: > it can't reboot which imho a very basic feature, what's more can't even > shutdown/poweroff. the centos i386 guest are not able to shutdown on the > x86_64 host (strange the x86_64 centos and the i586 mandrake-9 are able > to shutdown) or what's seems to be more likely it's a random think. > this issue is known and will be fix soon. > can't give 2GB ram to any guests not even 2, but 1. is ok. what's > more i've to discover this in the hard way virt-manager gives some > strange error message (anyway none of the virt-manager's error message > are useful, just strange stack trace without any kind of useful info). > kvm from version 36 support above 2giga of ram (it was tested with 32giga ram guest) > the host see as i've 4 cpu. i've got a change to gives more cpu to the > guest, what's more they starts, but after a few minutes running the > system crash. not just the guest os but the host os crash without any > kind of info, log or any useful info what was the cause of it, but hard > reset helps:-((( first of all it's serious problem, even if it's a known > bug and documented somewhere (but there is not any kind of docs about > neither kvm nor virt-manager/libvirt and what i can find that very > limited), since all of the new hvm cpu (which is required for kvm) has > more core, so the guest can't use the real power of the cpu this means > i've to put a lots of guests with one virtual cpu to the host or > currently can't exploit these cpus. > > libvirt not start the guest when the host started, not saved the state > of the guests when stopped, when restarted all guest get into shutdown > state. may be it's just libvirt but, but if kvm not able to save it's > guest's state that it's a real pain. this behavior not acceptable in a > real environment. > > in virt-manager can't modify virtual cpu number of the guests > (virt-manager crash with another unusable stacks trace). it i modify the > xml config file by hand i've to restart libvirt in order to read it. > even if i just modify one guest's config, but as if i restart libvirtd > the all other guest will be killed it's another nice feature. > > from vit-manager i can't assign swap partitions (and any other device > to the guests) during guest creation. i precreate lvm partition on the > host for root and swap to all of our guests (about 10) but it's a real > pain to reload libvirtd (which kills all guests) to add a new disk to > the guest which can be used as a swap or other partition. what's more > it'd be useful to add swap partition during install. the same thing > apply to cdrom too. > > if i made a mistake in the libvirtd xml config file, then i don't get > any kind of error message just libvirt don't start the given guest. no > error message service seems to start without error and don't know what > was the reason that the guest not start (sometimes because syntactic > error in the config file, sometimes kvm/qemu not support it eg more then > 2gb mem). there are unwritten unix/linux tradition eg if there are error > during a service startup report it some log file. if a service can't > start without error then it not start at all eg. if i've apache with 5 > virtual host but one of it's config has error then the whole httpd not > started. it'd have to be the same with libvirt too. > > libvirt config file has all the features as qemu command line (if not it > can't be used by advanced users)? but i don't know since there is not a > reference docs for the config file. > > there is not a detailed reference docs about libvirtd config (and at the > same time the gui not contains all the settings). for the the xml format > is a bit redundant eg. "source dev", "target dev" why not just source > and target, inside interface type='bridge' 'source bridge' why not just > source (i've to modify two place when i'd like to switch from network to > bride. ok these are just small cosmetic thing just mention. > > when create a new guest in virt-manager and reach the last page and > press finish then most of the time (2 times from 3) i've got an error > something like "can't connect to qemu" after i press ok and press again > finish then it's able to create the new host (so always have to retry it). > > in virt-manager when a guest is sh
Re: [kvm-devel] (long) kvm and virt-manager not ready for daily usage
On 9/8/07, Farkas Levente <[EMAIL PROTECTED]> wrote: > kvm is not ready for production use for many reason: > it can't reboot which imho a very basic feature, what's more can't even > shutdown/poweroff. the centos i386 guest are not able to shutdown on the > x86_64 host (strange the x86_64 centos and the i586 mandrake-9 are able > to shutdown) or what's seems to be more likely it's a random think. Reboot failure is a regression; for shutdown you should enable APCI with "acpi=force"; bochs BIOS doesn't have SMBIOS/DMI tables and Linux may refuse to use ACPI without them (it depends on the configuration). Luca - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
[kvm-devel] Intel-only or AMD Opteron as well?
Hi, This is my first message to the list, and I've just discovered KVM... so please have patience with my (probably stupid and answered in some FAQ already ;) questions... The first question that comes to mind is that the project description mentions Intel's virtualization features... I don't have an Intel CPU. I have a dual-core AMD Opteron 2216 (Socket F, code-name Santa Rosa) http://www.chiplist.com/AMD_Opteron_DP_HE_2000_series_Dual_Core_processor_Santa_Rosa_Rev_F_High_Efficiency/tree3f-subsection--2269-/ It supposedly includes AMD's virtualization features, aka "Pacifica". The $1M (or $0.02) question is... does KVM include any optimizations for the AMD virtualization extensions? Or should I look at other solutions like VMWare or VirtualBox? Thanks, Fernando -- Dream of the Daily Mail It is the Holy Grail And then the BBC Your life would be complete -Manic Street Preachers, "Royal Correspondent" - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/___ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
Re: [kvm-devel] (long) kvm and virt-manager not ready for daily usage
Luca wrote: > On 9/8/07, Farkas Levente <[EMAIL PROTECTED]> wrote: >> kvm is not ready for production use for many reason: >> it can't reboot which imho a very basic feature, what's more can't even >> shutdown/poweroff. the centos i386 guest are not able to shutdown on the >> x86_64 host (strange the x86_64 centos and the i586 mandrake-9 are able >> to shutdown) or what's seems to be more likely it's a random think. > > Reboot failure is a regression; for shutdown you should enable APCI > with "acpi=force"; bochs BIOS doesn't have SMBIOS/DMI tables and Linux > may refuse to use ACPI without them (it depends on the configuration). when, where, how? is there any docs about it? -- Levente "Si vis pacem para bellum!" - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
Re: [kvm-devel] Intel-only or AMD Opteron as well?
On 9/8/07, Fernando Cassia <[EMAIL PROTECTED]> wrote: > > This is my first message to the list, and I've just discovered KVM... so > please have patience with my (probably stupid and answered in some FAQ > already ;) questions... Yep, it's in the FAQ: http://kvm.qumranet.com/kvmwiki/FAQ#head-089ef3cae348adfe76a2e614b3c551f811d71234 http://kvm.qumranet.com/kvmwiki/FAQ#head-a78f5f083749cb9c2e57d7d4efaf2ecf25b9db60 http://kvm.qumranet.com/kvmwiki/FAQ#head-1c0d0eb479b0cbd8cd4b2d04e3d8fbc9710ba666 > It supposedly includes AMD's virtualization features, aka "Pacifica". > The $1M (or $0.02) question is... does KVM include any optimizations for the > AMD virtualization extensions? Yes, load kvm-amd. Luca - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
Re: [kvm-devel] (long) kvm and virt-manager not ready for daily usage
On 9/8/07, Farkas Levente <[EMAIL PROTECTED]> wrote: > Luca wrote: > > On 9/8/07, Farkas Levente <[EMAIL PROTECTED]> wrote: > >> kvm is not ready for production use for many reason: > >> it can't reboot which imho a very basic feature, what's more can't even > >> shutdown/poweroff. the centos i386 guest are not able to shutdown on the > >> x86_64 host (strange the x86_64 centos and the i586 mandrake-9 are able > >> to shutdown) or what's seems to be more likely it's a random think. > > > > Reboot failure is a regression; for shutdown you should enable APCI > > with "acpi=force"; bochs BIOS doesn't have SMBIOS/DMI tables and Linux > > may refuse to use ACPI without them (it depends on the configuration). > > when, where, how? is there any docs about it? Add "acpi=force" on guest kernel command line. Luca - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
Re: [kvm-devel] Intel-only or AMD Opteron as well?
Fernando Cassia wrote: > Hi, > > This is my first message to the list, and I've just discovered KVM... > so please have patience with my (probably stupid and answered in some > FAQ already ;) questions... > > The first question that comes to mind is that the project description > mentions Intel's virtualization features... > > I don't have an Intel CPU. I have a dual-core AMD Opteron 2216 (Socket > F, code-name Santa Rosa) > > http://www.chiplist.com/AMD_Opteron_DP_HE_2000_series_Dual_Core_processor_Santa_Rosa_Rev_F_High_Efficiency/tree3f-subsection--2269-/ > > It supposedly includes AMD's virtualization features, aka "Pacifica". > The $1M (or $0.02) question is... does KVM include any optimizations > for the AMD extensions? Or should I look at other solutions like > VMWare or VirtualBox? > kvm have support to amd virtualization extensions., you your cpu have it, you should have no problem to use kvm. > - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
Re: [kvm-devel] Intel-only or AMD Opteron as well?
On 9/8/07, Izik Eidus <[EMAIL PROTECTED]> wrote: > > > > > kvm have support to amd virtualization extensions., you your cpu have > it, you should have no problem to use kvm. > > > That's great!!. The more I read about KVM the more I like it!. Point #1: I just wish someone had thought more about the name before selecting "KVM" ... because Sun has been using KVM (the K Virtual Machine) for its Java VM for embedded devices for some time. This just causes confusion on web searches... The K Virtual Machine (KVM) http://java.sun.com/products/cldc/wp/ In any case... choosing somthing like "Kernel-VM" instead of the KVM moniker would have been less confusing. But hey... no big deal... but still if you ever decide to change the name... Point #2: I'm very happy (yet a bit surprised) to see RedHat has simultaneously embraced KVM for the Fedora 7 desktop, and Xen for the next RedHat Enterprise Server. Red Hat endorses KVM virtualization http://news.com.com/2100-1016_3-6159528.html ^ this just shows to me that Red Hat continues being the smartest Linux vendor out there IMHO! (from the desktop selection -Gnome vs KDE- to its support for Java (JBoss), and now to virtualization (KVM), ... unlike some other Linux vendor out there that like to do pacts with Redmond and include other proprietary VM technologies ;) Point #3: Xen vs KVM... I'm confused The above move by RedHat is a bit confusing... what can Xen do that KVM cannot?. In other words, why should anyone even bother with Xen with KVM around ??. I've read Xen is "more robust" because it has a "one year lead" over KVM. But really, how does this translate, if performance of Xen could be worse due to more paravirtualization?. Or is Xen more optimized to provide the "greatest possible consolidation" on servers (ie less resource usage, less impact on cpu usage of a high number of VMs?). Finally... after reading about Xen and KVM(this KVM, not Sun's ;), I wonder... the FAQ says Xen does more paravirtualization, whereas KVM uses the CPU's own virtualization features. Yet I visit some articles like this one http://aplawrence.com/Linux/kvm_virtualization.html which claims that Xen is "THE FASTEST" approach to virtualization. How can it be faster since it uses paravirtualization (software) instead of direct hardware virtualization features as KVM? =[quote]== Xen http://www.xensource.com/ "Its goal is to provide very high performance. It is probably the fastest hypervisor you can find and it achieves this through 'paravirtualization'. " = Sorry again... I'm just trying to understand the "big picture"... FC -- Dream of the Daily Mail It is the Holy Grail And then the BBC Your life would be complete -Manic Street Preachers, "Royal Correspondent" - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/___ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
Re: [kvm-devel] (long) kvm and virt-manager not ready for daily usage
On Sat, 2007-09-08 at 13:15 +0200, Farkas Levente wrote: > hi, > kvm is not ready for production use for many reason: > it can't reboot which imho a very basic feature, what's more can't even > shutdown/poweroff. the centos i386 guest are not able to shutdown on the > x86_64 host (strange the x86_64 centos and the i586 mandrake-9 are able > to shutdown) or what's seems to be more likely it's a random think. > > can't give 2GB ram to any guests not even 2, but 1. is ok. what's > more i've to discover this in the hard way virt-manager gives some > strange error message (anyway none of the virt-manager's error message > are useful, just strange stack trace without any kind of useful info). kvm-36 now supports more than 2GB of RAM per guest. You're one version off for that. > the host see as i've 4 cpu. i've got a change to gives more cpu to the > guest, what's more they starts, but after a few minutes running the > system crash. not just the guest os but the host os crash without any > kind of info, log or any useful info what was the cause of it, but hard > reset helps:-((( first of all it's serious problem, even if it's a known > bug and documented somewhere (but there is not any kind of docs about > neither kvm nor virt-manager/libvirt and what i can find that very > limited), since all of the new hvm cpu (which is required for kvm) has > more core, so the guest can't use the real power of the cpu this means > i've to put a lots of guests with one virtual cpu to the host or > currently can't exploit these cpus. I'm having difficulty understanding what your problem is. Are you saying that guest SMP isn't working for you? The host OS definitely shouldn't crash. Can you be more specific about what configs you are using? There was a host oops fixed in kvm-36 so upgrading may help you. Regards, Anthony Liguori > libvirt not start the guest when the host started, not saved the state > of the guests when stopped, when restarted all guest get into shutdown > state. may be it's just libvirt but, but if kvm not able to save it's > guest's state that it's a real pain. this behavior not acceptable in a > real environment. > > in virt-manager can't modify virtual cpu number of the guests > (virt-manager crash with another unusable stacks trace). it i modify the > xml config file by hand i've to restart libvirt in order to read it. > even if i just modify one guest's config, but as if i restart libvirtd > the all other guest will be killed it's another nice feature. > > from vit-manager i can't assign swap partitions (and any other device > to the guests) during guest creation. i precreate lvm partition on the > host for root and swap to all of our guests (about 10) but it's a real > pain to reload libvirtd (which kills all guests) to add a new disk to > the guest which can be used as a swap or other partition. what's more > it'd be useful to add swap partition during install. the same thing > apply to cdrom too. > > if i made a mistake in the libvirtd xml config file, then i don't get > any kind of error message just libvirt don't start the given guest. no > error message service seems to start without error and don't know what > was the reason that the guest not start (sometimes because syntactic > error in the config file, sometimes kvm/qemu not support it eg more then > 2gb mem). there are unwritten unix/linux tradition eg if there are error > during a service startup report it some log file. if a service can't > start without error then it not start at all eg. if i've apache with 5 > virtual host but one of it's config has error then the whole httpd not > started. it'd have to be the same with libvirt too. > > libvirt config file has all the features as qemu command line (if not it > can't be used by advanced users)? but i don't know since there is not a > reference docs for the config file. > > there is not a detailed reference docs about libvirtd config (and at the > same time the gui not contains all the settings). for the the xml format > is a bit redundant eg. "source dev", "target dev" why not just source > and target, inside interface type='bridge' 'source bridge' why not just > source (i've to modify two place when i'd like to switch from network to > bride. ok these are just small cosmetic thing just mention. > > when create a new guest in virt-manager and reach the last page and > press finish then most of the time (2 times from 3) i've got an error > something like "can't connect to qemu" after i press ok and press again > finish then it's able to create the new host (so always have to retry it). > > in virt-manager when a guest is shutdown and double-click on the guest > and try to start it it's not possible. you've to select the guest in the > main windows, right-click and start it. > > the new vnc based console is very unstable or just virt-manager not able > to connect it. many times i double click on a guest in virt-manager i > got the window can't connect to console while th
Re: [kvm-devel] Intel-only or AMD Opteron as well?
On 9/8/07, Fernando Cassia <[EMAIL PROTECTED]> wrote: > Point #3: Xen vs KVM... I'm confused > > The above move by RedHat is a bit confusing... what can Xen do that KVM > cannot?. In other words, why should anyone even bother with Xen with KVM > around ??. Xen is probably more mature, and has more more management tools. Plus it's already known and deployed in the enterprise world. On the downside Xen is big, while KVM is simpler. > I've read Xen is "more robust" because it has a "one year lead" > over KVM. But really, how does this translate, if performance of Xen could > be worse due to more paravirtualization?. Paravirtualization is not a bad thing ;-) If you cannot modify the guest then of course a fully virtualized VM is needed, but if you can modify it (by e.g. loading a special driver) then PV is likely to give some speed enhancements. The first obvious area for PV is device drivers: emulating a network card (or a disk controller, or...) wastes a lot of cycles, it makes lots of sense to use a special driver virtualization-aware driver that speeds up the communication between the guest and the host. VirtIO for example is all about flipping pages between guest and host. Another class of operations the can be PVirtualized are privileged instructions that may affect the global state of the machine. E.g. you don't want the guest to be able to _really_ turn interrupts off; instead you trap the 'cli' and stop sending interrupts to it. If the guest is aware of the virtualization it can politely ask the guest to stop interrupt delivery (instead of going through trap+emulate). ATM Linux supports the paravirt_ops infrastructure that covers interrupts delivery, page table / MMU management, APIC, MSR (and maybe other stuff). This second class of PV ops requires modification of core parts of the guest operating system; while it's certainly possible to create a win32 driver for e.g. a PV network card it's impossible to do the same for paravirt_ops. > Or is Xen more optimized to > provide the "greatest possible consolidation" on servers (ie less resource > usage, less impact on cpu usage of a high number of VMs?). Xen supported paravirt-only guest, but gained support for full virtualization. KVM started as full virtualization solution but is now gaining PV support (at least for network and block devices - I think kvm-lite will go further). > Finally... after reading about Xen and KVM(this KVM, not Sun's ;), I > wonder... the FAQ says Xen does more paravirtualization, whereas KVM uses > the CPU's own virtualization features. Yet I visit some articles like this > one > > http://aplawrence.com/Linux/kvm_virtualization.html > > which claims that Xen is "THE FASTEST" approach to virtualization. How can > it be faster since it uses paravirtualization (software) instead of direct > hardware virtualization features as KVM? See above. Doing software _emulation_ of the guest is slow. A PV guest can coordinate very efficiently with the host. Luca - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
Re: [kvm-devel] Intel-only or AMD Opteron as well?
On Sat, 2007-09-08 at 19:01 +0200, Luca wrote: > On 9/8/07, Fernando Cassia <[EMAIL PROTECTED]> wrote: > > Point #3: Xen vs KVM... I'm confused > > > > The above move by RedHat is a bit confusing... what can Xen do that KVM > > cannot?. In other words, why should anyone even bother with Xen with KVM > > around ??. > > Xen is probably more mature, and has more more management tools. Plus > it's already known and deployed in the enterprise world. On the > downside Xen is big, while KVM is simpler. Keep in mind, the referenced article is very old (it's from February). > > I've read Xen is "more robust" because it has a "one year lead" > > over KVM. But really, how does this translate, if performance of Xen could > > be worse due to more paravirtualization?. > > Paravirtualization is not a bad thing ;-) If you cannot modify the > guest then of course a fully virtualized VM is needed, but if you can > modify it (by e.g. loading a special driver) then PV is likely to give > some speed enhancements. > The first obvious area for PV is device drivers: emulating a network > card (or a disk controller, or...) wastes a lot of cycles, it makes > lots of sense to use a special driver virtualization-aware driver that > speeds up the communication between the guest and the host. VirtIO for > example is all about flipping pages between guest and host. > Another class of operations the can be PVirtualized are privileged > instructions that may affect the global state of the machine. E.g. you > don't want the guest to be able to _really_ turn interrupts off; > instead you trap the 'cli' and stop sending interrupts to it. If the > guest is aware of the virtualization it can politely ask the guest to > stop interrupt delivery (instead of going through trap+emulate). One thing to keep in mind is that in this example, hardware virtualization eliminates the need to trap and emulate cli/sti. In general, there are two classes of paravirtualizations. The first are related to functionality on non-virtualization aware hardware (32-bit startup, cooperative descriptor table management, memory hole, etc.). The second class would be optimizations which includes things like page table update batching, paravirtual device drivers, etc. KVM is beginning to get the second class of optimizations. Once they are in place and mature, my expectation is that it will outperform things like Xen. Hardware virtualization is probably a lot faster than something that relies on only the first class of paravirtualizations. > > Finally... after reading about Xen and KVM(this KVM, not Sun's ;), I > > wonder... the FAQ says Xen does more paravirtualization, whereas KVM uses > > the CPU's own virtualization features. Yet I visit some articles like this > > one > > > > http://aplawrence.com/Linux/kvm_virtualization.html > > > > which claims that Xen is "THE FASTEST" approach to virtualization. How can > > it be faster since it uses paravirtualization (software) instead of direct > > hardware virtualization features as KVM? > > See above. Doing software _emulation_ of the guest is slow. A PV guest > can coordinate very efficiently with the host. Well, it's not really that simple. There are some things Xen is very slow at (especially with 64-bit guests). The best thing to do when trying to decide which virtualization solution to use is to evaluate all options for the workloads you're interested in. Regards, Anthony Liguori > Luca > > - > This SF.net email is sponsored by: Microsoft > Defy all challenges. Microsoft(R) Visual Studio 2005. > http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ > ___ > kvm-devel mailing list > kvm-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/kvm-devel - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
Re: [kvm-devel] (long) kvm and virt-manager not ready for daily usage
Anthony Liguori wrote: >> the host see as i've 4 cpu. i've got a change to gives more cpu to the >> guest, what's more they starts, but after a few minutes running the >> system crash. not just the guest os but the host os crash without any >> kind of info, log or any useful info what was the cause of it, but hard >> reset helps:-((( first of all it's serious problem, even if it's a known >> bug and documented somewhere (but there is not any kind of docs about >> neither kvm nor virt-manager/libvirt and what i can find that very >> limited), since all of the new hvm cpu (which is required for kvm) has >> more core, so the guest can't use the real power of the cpu this means >> i've to put a lots of guests with one virtual cpu to the host or >> currently can't exploit these cpus. > > I'm having difficulty understanding what your problem is. Are you after i reread my sentences it was difficult for me too:-( > saying that guest SMP isn't working for you? The host OS definitely > shouldn't crash. Can you be more specific about what configs you are > using? There was a host oops fixed in kvm-36 so upgrading may help you. exactly. i've got 4 phisical core (Intel Core 2 Quad) and i try to give 4 cpus for 2 guests and 2 cpus for a third guest and restart libvirtd. the result was that even the host system crash without any stack trace or kernel panic and only the hard reset helps. -- Levente "Si vis pacem para bellum!" - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
Re: [kvm-devel] (long) kvm and virt-manager not ready for daily usage
On Sat, 2007-09-08 at 22:50 +0200, Farkas Levente wrote: > Anthony Liguori wrote: > >> the host see as i've 4 cpu. i've got a change to gives more cpu to the > >> guest, what's more they starts, but after a few minutes running the > >> system crash. not just the guest os but the host os crash without any > >> kind of info, log or any useful info what was the cause of it, but hard > >> reset helps:-((( first of all it's serious problem, even if it's a known > >> bug and documented somewhere (but there is not any kind of docs about > >> neither kvm nor virt-manager/libvirt and what i can find that very > >> limited), since all of the new hvm cpu (which is required for kvm) has > >> more core, so the guest can't use the real power of the cpu this means > >> i've to put a lots of guests with one virtual cpu to the host or > >> currently can't exploit these cpus. > > > > I'm having difficulty understanding what your problem is. Are you > > after i reread my sentences it was difficult for me too:-( > > > saying that guest SMP isn't working for you? The host OS definitely > > shouldn't crash. Can you be more specific about what configs you are > > using? There was a host oops fixed in kvm-36 so upgrading may help you. > > exactly. i've got 4 phisical core (Intel Core 2 Quad) and i try to give > 4 cpus for 2 guests and 2 cpus for a third guest and restart libvirtd. > the result was that even the host system crash without any stack trace > or kernel panic and only the hard reset helps. Could you try to reproduce the problem with kvm-36? Host crash bugs are very important to fix especially one so easily reproducible. Regards, Anthony Liguori - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
Re: [kvm-devel] sharing memory
Cam Macdonell wrote: > Dor Laor wrote: >> >> In the guest you need the matching pci driver. Currently you can you the >> attached one, >> I'm not sure if it is uptodate. Soon we'll post a device that uses >> virtio for the vmchannel. >> -Dor > > Would the existing hypercall.c that is in kvm-userspace/drivers/ work > as well. What is the difference? > > Thanks, > Cam > The existing hypercall driver should do the work too. Actually I forgot about it when I posted the new one. The one I sent might be half baked, you might be better of with the drivers/hypercal.c Anyway we will soon rebase it over virtio. -Dor - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
