Hello listmates, Let''s say I''ve got a machine with 1 GB of RAM and I want to host 3 512 MB virtual machines on it? Is that possible - i.e., is it possible to force Xen to use swap and pass it off as RAM to the VM''s? I know it is slow and inefficient but for the purposes of testing - is that possible? Thanks. Boris. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
You can use swap of any size at VM level (every VM will have it own swap). Right now there is no way to do hypervisor swap or oversell memory. В Птн, 24/09/2010 в 13:14 -0400, Boris Epstein пишет:> Hello listmates, > > Let''s say I''ve got a machine with 1 GB of RAM and I want to host 3 512 > MB virtual machines on it? Is that possible - i.e., is it possible to > force Xen to use swap and pass it off as RAM to the VM''s? I know it is > slow and inefficient but for the purposes of testing - is that > possible? > > Thanks. > > Boris. > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Hi! The Xen 4.0 introduces the TMEM project, take a look at it: http://wiki.xensource.com/xenwiki/Xen4.0 <http://wiki.xensource.com/xenwiki/Xen4.0> TMEM allows improved utilization of unused (for example page cache) PV guest memory. more information: http://oss.oracle.com/projects/tmem/ Cheers! Thiago <http://oss.oracle.com/projects/tmem/> On 24 September 2010 14:46, George Shuklin <george.shuklin@gmail.com> wrote:> You can use swap of any size at VM level (every VM will have it own > swap). > > Right now there is no way to do hypervisor swap or oversell memory. > > В Птн, 24/09/2010 в 13:14 -0400, Boris Epstein пишет: > > Hello listmates, > > > > Let''s say I''ve got a machine with 1 GB of RAM and I want to host 3 512 > > MB virtual machines on it? Is that possible - i.e., is it possible to > > force Xen to use swap and pass it off as RAM to the VM''s? I know it is > > slow and inefficient but for the purposes of testing - is that > > possible? > > > > Thanks. > > > > Boris. > > > > _______________________________________________ > > Xen-users mailing list > > Xen-users@lists.xensource.com > > http://lists.xensource.com/xen-users > > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Yes, It is nice technology, but it still do not allow hypervisor swapping or overselling. :) В Птн, 24/09/2010 в 14:57 -0300, Martinx - ジェームズ пишет:> Hi!> The Xen 4.0 introduces the TMEM project, take a look at it:> http://wiki.xensource.com/xenwiki/Xen4.0> TMEM allows improved utilization of unused (for example page cache) > PV guest memory. more > information: http://oss.oracle.com/projects/tmem/ >> On 24 September 2010 14:46, George Shuklin <george.shuklin@gmail.com> > wrote: > You can use swap of any size at VM level (every VM will have > it own > swap). > > Right now there is no way to do hypervisor swap or oversell > memory. > > В Птн, 24/09/2010 в 13:14 -0400, Boris Epstein пишет: > > > Hello listmates, > > > > Let''s say I''ve got a machine with 1 GB of RAM and I want to > host 3 512 > > MB virtual machines on it? Is that possible - i.e., is it > possible to > > force Xen to use swap and pass it off as RAM to the VM''s? I > know it is > > slow and inefficient but for the purposes of testing - is > that > > possible? > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Mmm... You mean this: http://blog.xen.org/index.php/2008/08/27/xen-33-feature-memory-overcommit/ <http://blog.xen.org/index.php/2008/08/27/xen-33-feature-memory-overcommit/> ? On 24 September 2010 15:49, George Shuklin <george.shuklin@gmail.com> wrote:> Yes, It is nice technology, but it still do not allow hypervisor > swapping or overselling. :) > > В Птн, 24/09/2010 в 14:57 -0300, Martinx - ジェームズ пишет: > > Hi! > > > The Xen 4.0 introduces the TMEM project, take a look at it: > > > http://wiki.xensource.com/xenwiki/Xen4.0 > > > TMEM allows improved utilization of unused (for example page cache) > > PV guest memory. more > > information: http://oss.oracle.com/projects/tmem/ > > > > > On 24 September 2010 14:46, George Shuklin <george.shuklin@gmail.com> > > wrote: > > You can use swap of any size at VM level (every VM will have > > it own > > swap). > > > > Right now there is no way to do hypervisor swap or oversell > > memory. > > > > В Птн, 24/09/2010 в 13:14 -0400, Boris Epstein пишет: > > > > > Hello listmates, > > > > > > Let''s say I''ve got a machine with 1 GB of RAM and I want to > > host 3 512 > > > MB virtual machines on it? Is that possible - i.e., is it > > possible to > > > force Xen to use swap and pass it off as RAM to the VM''s? I > > know it is > > > slow and inefficient but for the purposes of testing - is > > that > > > possible? > > > > > > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Nope. Ballooning is cool mechanism, but it is not overcommitment. We can say ''theoretical overcommitment'' - if we starting few machines with mem=1GiB maxmem=10GiB, we (theoretically) give every machine 10G, but this is not overcommitment, it just limits, raised up beyond host memory. Actual overcommitment/oversell is when sum of actually allocated memory (as displayed by ''free'' in every guest) is more then memory on host. Xen lack of this feature and I believe this make it more pricey in term of VPS/VDS hosting, but much better quality for end-users (domUs), compare to OpenVZ overcommitment. В Птн, 24/09/2010 в 16:24 -0300, Martinx - ジェームズ пишет:> Mmm... You mean this: > > > http://blog.xen.org/index.php/2008/08/27/xen-33-feature-memory-overcommit/ > > > ? > > On 24 September 2010 15:49, George Shuklin <george.shuklin@gmail.com> > wrote: > Yes, It is nice technology, but it still do not allow > hypervisor > swapping or overselling. :) > > В Птн, 24/09/2010 в 14:57 -0300, Martinx - ジェームズ пишет: > > Hi! > > > The Xen 4.0 introduces the TMEM project, take a look at it: > > > http://wiki.xensource.com/xenwiki/Xen4.0 > > > TMEM allows improved utilization of unused (for example > page cache) > > PV guest memory. more > > information: http://oss.oracle.com/projects/tmem/ > > > > > > On 24 September 2010 14:46, George Shuklin > <george.shuklin@gmail.com> > > wrote: > > You can use swap of any size at VM level (every VM > will have > > it own > > swap). > > > > Right now there is no way to do hypervisor swap or > oversell > > memory. > > > > В Птн, 24/09/2010 в 13:14 -0400, Boris Epstein > пишет: > > > > > Hello listmates, > > > > > > Let''s say I''ve got a machine with 1 GB of RAM and > I want to > > host 3 512 > > > MB virtual machines on it? Is that possible - > i.e., is it > > possible to > > > force Xen to use swap and pass it off as RAM to > the VM''s? I > > know it is > > > slow and inefficient but for the purposes of > testing - is > > that > > > possible? > > > > > > > > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users > > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Okay, I understand... And what about the Linux Kernel Samepage Merging feature? http://www.linux-kvm.com/content/using-ksm-kernel-samepage-merging-kvm <http://www.linux-kvm.com/content/using-ksm-kernel-samepage-merging-kvm> But I don''t know if Xen can take advantage of it... I my Ubuntu 10.04 Desktop, I have 4G of RAM and I can bootup ~6 clone VMs with 1024M of RAM for each... On 24 September 2010 18:53, George Shuklin <george.shuklin@gmail.com> wrote:> Nope. > > Ballooning is cool mechanism, but it is not overcommitment. We can say > ''theoretical overcommitment'' - if we starting few machines with mem=1GiB > maxmem=10GiB, we (theoretically) give every machine 10G, but this is not > overcommitment, it just limits, raised up beyond host memory. > > Actual overcommitment/oversell is when sum of actually allocated memory > (as displayed by ''free'' in every guest) is more then memory on host. > > Xen lack of this feature and I believe this make it more pricey in term > of VPS/VDS hosting, but much better quality for end-users (domUs), > compare to OpenVZ overcommitment. > > > Ё Ё宇тЁ, 24/09/2010 Ё 16:24 -0300, Martinx - ジェА璽爛 Ё瓰иЁ螂еЁ: > > Mmm... You mean this: > > > > > > > http://blog.xen.org/index.php/2008/08/27/xen-33-feature-memory-overcommit/ > > > > > > ? > > > > On 24 September 2010 15:49, George Shuklin <george.shuklin@gmail.com> > > wrote: > > Yes, It is nice technology, but it still do not allow > > hypervisor > > swapping or overselling. :) > > > > Ё Ё宇тЁ, 24/09/2010 Ё 14:57 -0300, Martinx - ジェА璽爛 Ё瓰иЁ螂еЁ: > > > Hi! > > > > > The Xen 4.0 introduces the TMEM project, take a look at it: > > > > > http://wiki.xensource.com/xenwiki/Xen4.0 > > > > > TMEM allows improved utilization of unused (for example > > page cache) > > > PV guest memory. more > > > information: http://oss.oracle.com/projects/tmem/ > > > > > > > > > > On 24 September 2010 14:46, George Shuklin > > <george.shuklin@gmail.com> > > > wrote: > > > You can use swap of any size at VM level (every VM > > will have > > > it own > > > swap). > > > > > > Right now there is no way to do hypervisor swap or > > oversell > > > memory. > > > > > > Ё Ё宇тЁ, 24/09/2010 Ё 13:14 -0400, Boris Epstein > > Ё瓰иЁ螂еЁ: > > > > > > > Hello listmates, > > > > > > > > Let''s say I''ve got a machine with 1 GB of RAM and > > I want to > > > host 3 512 > > > > MB virtual machines on it? Is that possible - > > i.e., is it > > > possible to > > > > force Xen to use swap and pass it off as RAM to > > the VM''s? I > > > know it is > > > > slow and inefficient but for the purposes of > > testing - is > > > that > > > > possible? > > > > > > > > > > > > > > > > > > _______________________________________________ > > Xen-users mailing list > > Xen-users@lists.xensource.com > > http://lists.xensource.com/xen-users > > > > > > > > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users