Hi @all, I''ve read in many posts, that XEN limits the 32 bit PAE kernel to 16 GB RAM, but I don''t find were to enable more. Starting linux without XEN shows the whole memory. Is there still no solution? I don''t have the possibility to upgrade the server to 64 bit. Thanks Daniel _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On 08/02/2011 07:27, "Daniel Bauer" <mlist@dsb-gmbh.de> wrote:> Hi @all, > > I''ve read in many posts, that XEN limits the 32 bit PAE kernel to 16 GB > RAM, but I don''t find were to enable more. Starting linux without XEN > shows the whole memory. Is there still no solution? > > I don''t have the possibility to upgrade the server to 64 bit.Then no. -- Keir> Thanks > Daniel > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Tue, Feb 08, 2011 at 08:27:02AM +0100, Daniel Bauer wrote:> Hi @all, > > I''ve read in many posts, that XEN limits the 32 bit PAE kernel to 16 GB > RAM, but I don''t find were to enable more. Starting linux without XEN > shows the whole memory. Is there still no solution? > > I don''t have the possibility to upgrade the server to 64 bit. >You can run 64bit hypervisor (xen.gz) with a 32bit PAE dom0 Linux kernel. Maybe that''s an option for you.. That allows you to use all the available memory for VMs, and dedicate some memory (say, 1GB) for a 32bit dom0. -- Pasi _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Hallo Pasi, From: "Pasi Kärkkäinen"> On Tue, Feb 08, 2011 at 08:27:02AM +0100, Daniel Bauer wrote: >> I''ve read in many posts, that XEN limits the 32 bit PAE kernel to 16 >> GB >> RAM, but I don''t find were to enable more. Starting linux without XEN >> shows the whole memory. Is there still no solution? >> >> I don''t have the possibility to upgrade the server to 64 bit. >> > > You can run 64bit hypervisor (xen.gz) with a 32bit PAE dom0 Linux > kernel. > Maybe that''s an option for you..if it works, why not! But what are the issues about this solution?> That allows you to use all the available memory for VMs, and dedicate > some memory (say, 1GB) for a 32bit dom0.sounds really good, I''ll try this asap. Thank you Daniel _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Hi Keir, From: "Keir Fraser"> On 08/02/2011 07:27, "Daniel Bauer" <mlist@dsb-gmbh.de> wrote: >> I''ve read in many posts, that XEN limits the 32 bit PAE kernel to 16 >> GB >> RAM, but I don''t find were to enable more. Starting linux without XEN >> shows the whole memory. Is there still no solution? >> >> I don''t have the possibility to upgrade the server to 64 bit. > > Then no.maybe a silly question, but who sets this limit? IMHO xen, because a "normal" bigmem kernel accepts upto 64 GB RAM. Is there really no switch to increase the RAM under a 32 bit kernel? Thanks a lot Daniel _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Tue, 2011-02-08 at 10:42 +0000, Daniel Bauer wrote:> Hallo Pasi, > > From: "Pasi Kärkkäinen" > > On Tue, Feb 08, 2011 at 08:27:02AM +0100, Daniel Bauer wrote: > >> I''ve read in many posts, that XEN limits the 32 bit PAE kernel to 16 > >> GB > >> RAM, but I don''t find were to enable more. Starting linux without XEN > >> shows the whole memory. Is there still no solution? > >> > >> I don''t have the possibility to upgrade the server to 64 bit. > >> > > > > You can run 64bit hypervisor (xen.gz) with a 32bit PAE dom0 Linux > > kernel. > > Maybe that''s an option for you.. > > if it works, why not! But what are the issues about this solution?None really. It''s certainly preferable to run a 64 bit hypervisor whenever possible but running a 32 bit domain 0 is a very reasonable configuration. It''s the default for XCP and XenServer for example and works quite well there.> > That allows you to use all the available memory for VMs, and dedicate > > some memory (say, 1GB) for a 32bit dom0.It also allows you to run a mixture of 32 and 64 bit guests. Ian. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Tue, 2011-02-08 at 10:42 +0000, Daniel Bauer wrote:> Hi Keir, > > From: "Keir Fraser" > > On 08/02/2011 07:27, "Daniel Bauer" <mlist@dsb-gmbh.de> wrote: > >> I''ve read in many posts, that XEN limits the 32 bit PAE kernel to 16 > >> GB > >> RAM, but I don''t find were to enable more. Starting linux without XEN > >> shows the whole memory. Is there still no solution? > >> > >> I don''t have the possibility to upgrade the server to 64 bit. > > > > Then no. > > maybe a silly question, but who sets this limit? IMHO xen, because a > "normal" bigmem kernel accepts upto 64 GB RAM. Is there really no switch > to increase the RAM under a 32 bit kernel?The limitation is due to the 32 bit hypervisor, not the kernel. In my experience a 32 bit (PAE) kernel running on a 64 bit hypervisor works just fine with up to 32GB. In theory up to 160GB is possible in the hypervisor<->PAE-kernel ABI but the kernel tends to run out of lowmem in the 50-60GB range depending on your .config -- this true of native too. Ian. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Hi Ian, From: "Ian Campbell"> On Tue, 2011-02-08 at 10:42 +0000, Daniel Bauer wrote: >> From: "Pasi Kärkkäinen" >> > On Tue, Feb 08, 2011 at 08:27:02AM +0100, Daniel Bauer wrote: >> >> I''ve read in many posts, that XEN limits the 32 bit PAE kernel to >> >> 16 >> >> GB >> >> RAM, but I don''t find were to enable more. Starting linux without >> >> XEN >> >> shows the whole memory. Is there still no solution? >> >> >> >> I don''t have the possibility to upgrade the server to 64 bit. >> >> >> > >> > You can run 64bit hypervisor (xen.gz) with a 32bit PAE dom0 Linux >> > kernel. >> > Maybe that''s an option for you.. >> >> if it works, why not! But what are the issues about this solution? > > None really. > > It''s certainly preferable to run a 64 bit hypervisor whenever possible > but running a 32 bit domain 0 is a very reasonable configuration. > > It''s the default for XCP and XenServer for example and works quite > well > there. > >> > That allows you to use all the available memory for VMs, and >> > dedicate >> > some memory (say, 1GB) for a 32bit dom0. > > It also allows you to run a mixture of 32 and 64 bit guests.I just tried it now, but the system doesn''t boot. The reason why I can''t upgrade to 64 bit is, that the server is only a 32 bit box (HP ProLiant DL760 G2, 8 x 3 GHz Xeon, 64 GB RAM). IMHO I need a 64 Bit CPU to run the 64 bit xen.gz, or? Thanks Daniel _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
From: "Ian Campbell"> On Tue, 2011-02-08 at 10:42 +0000, Daniel Bauer wrote: >> From: "Keir Fraser" >> > On 08/02/2011 07:27, "Daniel Bauer" <mlist@dsb-gmbh.de> wrote: >> >> I''ve read in many posts, that XEN limits the 32 bit PAE kernel to >> >> 16 >> >> GB >> >> RAM, but I don''t find were to enable more. Starting linux without >> >> XEN >> >> shows the whole memory. Is there still no solution? >> >> >> >> I don''t have the possibility to upgrade the server to 64 bit. >> > >> > Then no. >> >> maybe a silly question, but who sets this limit? IMHO xen, because a >> "normal" bigmem kernel accepts upto 64 GB RAM. Is there really no >> switch >> to increase the RAM under a 32 bit kernel? > > The limitation is due to the 32 bit hypervisor, not the kernel.I know, but I don''t find the switch to configure more RAM than 16 GB. I thought that XEN limits it to 16 GB and I could change it and recompile everything.> In my experience a 32 bit (PAE) kernel running on a 64 bit hypervisor > works just fine with up to 32GB. In theory up to 160GB is possible in > the hypervisor<->PAE-kernel ABI but the kernel tends to run out of > lowmem in the 50-60GB range depending on your .config -- this true of > native too.It will be great if I could use 48 GB. Ciao Daniel _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Tue, 2011-02-08 at 11:30 +0000, Daniel Bauer wrote:> Hi Ian, > > From: "Ian Campbell" > > On Tue, 2011-02-08 at 10:42 +0000, Daniel Bauer wrote: > >> From: "Pasi Kärkkäinen" > >> > On Tue, Feb 08, 2011 at 08:27:02AM +0100, Daniel Bauer wrote: > >> >> I''ve read in many posts, that XEN limits the 32 bit PAE kernel to > >> >> 16 > >> >> GB > >> >> RAM, but I don''t find were to enable more. Starting linux without > >> >> XEN > >> >> shows the whole memory. Is there still no solution? > >> >> > >> >> I don''t have the possibility to upgrade the server to 64 bit. > >> >> > >> > > >> > You can run 64bit hypervisor (xen.gz) with a 32bit PAE dom0 Linux > >> > kernel. > >> > Maybe that''s an option for you.. > >> > >> if it works, why not! But what are the issues about this solution? > > > > None really. > > > > It''s certainly preferable to run a 64 bit hypervisor whenever possible > > but running a 32 bit domain 0 is a very reasonable configuration. > > > > It''s the default for XCP and XenServer for example and works quite > > well > > there. > > > >> > That allows you to use all the available memory for VMs, and > >> > dedicate > >> > some memory (say, 1GB) for a 32bit dom0. > > > > It also allows you to run a mixture of 32 and 64 bit guests. > > I just tried it now, but the system doesn''t boot. The reason why I can''t > upgrade to 64 bit is, that the server is only a 32 bit box (HP ProLiant > DL760 G2, 8 x 3 GHz Xeon, 64 GB RAM). IMHO I need a 64 Bit CPU to run > the 64 bit xen.gz, or?Er, yeah, you need a 64 bit processor.> > Thanks > Daniel > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Tue, 2011-02-08 at 11:32 +0000, Daniel Bauer wrote:> From: "Ian Campbell" > > On Tue, 2011-02-08 at 10:42 +0000, Daniel Bauer wrote: > >> From: "Keir Fraser" > >> > On 08/02/2011 07:27, "Daniel Bauer" <mlist@dsb-gmbh.de> wrote: > >> >> I''ve read in many posts, that XEN limits the 32 bit PAE kernel to > >> >> 16 > >> >> GB > >> >> RAM, but I don''t find were to enable more. Starting linux without > >> >> XEN > >> >> shows the whole memory. Is there still no solution? > >> >> > >> >> I don''t have the possibility to upgrade the server to 64 bit. > >> > > >> > Then no. > >> > >> maybe a silly question, but who sets this limit? IMHO xen, because a > >> "normal" bigmem kernel accepts upto 64 GB RAM. Is there really no > >> switch > >> to increase the RAM under a 32 bit kernel? > > > > The limitation is due to the 32 bit hypervisor, not the kernel. > > I know, but I don''t find the switch to configure more RAM than 16 GB. I > thought that XEN limits it to 16 GB and I could change it and recompile > everything.There is no switch, 16GB is a fundamental limitation of the 32 bit hypervisor. Ian. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Tue, Feb 08, 2011 at 12:32:19PM +0100, Daniel Bauer wrote:> From: "Ian Campbell" >> On Tue, 2011-02-08 at 10:42 +0000, Daniel Bauer wrote: >>> From: "Keir Fraser" >>> > On 08/02/2011 07:27, "Daniel Bauer" <mlist@dsb-gmbh.de> wrote: >>> >> I''ve read in many posts, that XEN limits the 32 bit PAE kernel to >>> >> 16 >>> >> GB >>> >> RAM, but I don''t find were to enable more. Starting linux without >>> >> XEN >>> >> shows the whole memory. Is there still no solution? >>> >> >>> >> I don''t have the possibility to upgrade the server to 64 bit. >>> > >>> > Then no. >>> >>> maybe a silly question, but who sets this limit? IMHO xen, because a >>> "normal" bigmem kernel accepts upto 64 GB RAM. Is there really no >>> switch >>> to increase the RAM under a 32 bit kernel? >> >> The limitation is due to the 32 bit hypervisor, not the kernel. > > I know, but I don''t find the switch to configure more RAM than 16 GB. I > thought that XEN limits it to 16 GB and I could change it and recompile > everything. > > >> In my experience a 32 bit (PAE) kernel running on a 64 bit hypervisor >> works just fine with up to 32GB. In theory up to 160GB is possible in >> the hypervisor<->PAE-kernel ABI but the kernel tends to run out of >> lowmem in the 50-60GB range depending on your .config -- this true of >> native too. > > It will be great if I could use 48 GB. >Hopefully you have realized having 48 GB of RAM on a 32bit Linux (no matter virtualized or not) will make it almost unusable? That''s because you''re running out of lowmem. -- Pasi _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
From: "Pasi Kärkkäinen" [...]> Hopefully you have realized having 48 GB of RAM > on a 32bit Linux (no matter virtualized or not) > will make it almost unusable? That''s because > you''re running out of lowmem.how do I see if this problem occurs? I run my ESXi 3.5 server on this boxes and don''t find any issues ... Thank you Daniel _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel