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Re: [Xen-devel] Migrate/Save of 32-bit domU Broken on Xen 3.1.2 64-bit dom0
Hi Dan, Dan Magenheimer wrote:
Joshua -- Why do you need so much memory on dom0? Are you thinking that the total memory available to guests is limited to what dom0 has? Or are you running some memory-hungry applications on dom0?
Hmm, I thought that a 32-bit dom0 system can only have up to 16GB of memory available to it and its domU's -- and a 64-bit dom0 can have a max of 32GB. I only allocate ~512MB of memory to the dom0's themselves. "xm info" shows us the rest of whats available for use by domU's.
Thus, even if I have 32GB of RAM in a server, the total memory that will be used in dom0 + all domU's can only add up to 16GB. Am I just plain old wrong?
Note that 64-bit Xen + 32-bit Dom0 will support both 32-bit and 64-bit domU's. (Oracle VM uses this configuration by default on 64-bit capable machines.) And save/restore/migration has been tested to work for this (with the patch Kurt posted).
Interesting. For some reason I thought that the Hypervisor had to match the dom0's kernel. So you're saying that if I compile the Xen Hypervisor as 64-bit and my dom0 + domU's both as 32-bit, I can reach the full capacity of my servers with respect to RAM (32GB) instead of being limited to 16GB? (And this only works with Kurt's patches?).
Dan-----Original Message----- From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx]On Behalf Of Joshua West Sent: Friday, January 18, 2008 4:06 PM To: Keir Fraser Cc: Kurt Hackel; xen-devel@xxxxxxxxxxxxxxxxxxxSubject: Re: [Xen-devel] Migrate/Save of 32-bit domU Broken on Xen 3.1.264-bit dom0 Dang, doesn't work in Xen 3.1.3-rc1 (like you said/expected), with or without Kurt's patches. Hmm... I thought 32-bit paravirtualized domU's on 64-bit dom0's were supported in Xen 3.1.x? Or am I mistaken? Perhaps standard features such as start/shutdown/pause of 32-bit PV domU's on 64-bit dom0's are supported, but not the more advancedmanagement features like save and migrate - and I was just unclear fromthe beginning? And of course... the final question that all developers hate... when s/could one _hope_ (not expect!) to see save/migrate functionality of 32-bit PV domU's on 64-bit dom0's? :-D Our whole reason for moving to 64-bit dom0's was to utilize 32GB of memory, instead of the 16GB limitation on 32-bit PAE dom0's. We can't convert all of our virtual machines (100+) to 64-bit linux as its too much work and some actually have to be 32-bit due to vendor suppliedsoftware (Oracle, Zimbra, etc). I suppose we'll wait to move to 64-bit until [live] migration is available, as its used quite frequently in ourmachine rooms. Thanks for all of your help Keir and Kurt. Keir Fraser wrote:Looking at the issues that need to be handled to supportthis, it cannot beexpected to work. -- Keir On 18/1/08 22:13, "Joshua West" <jwest@xxxxxxxxxxxx> wrote:Ahh. Well, I'm building xen-3.1.3-rc1 right now and I'llsee how that goes.Keir, have you seen this issue before? Where one cannotxm save/migratea 32-bit domU on a 64-bit dom0? Or is this expected towork and justdoesn't go well for me? Keir Fraser wrote:On 18/1/08 22:05, "Joshua West" <jwest@xxxxxxxxxxxx> wrote:Just to make sure the patches aren't the cause of this new errormessage, I'm going to see what happens with Xen3.1.3-rc1 w/o patches.Kurt, Keir, everybody else... any ideas as to why "xmsave" (and thus"xm migrate") of 32-bit domU's does not work on 64-bitdom0's? HasThe extent of the patches that Kurt posted indicate itsanybody found this to be successful in the past?pretty unlikely towork without considerable code modification. I guessthose patches aren'tquite fully baked yet, unfortunately, or haven't beenwritten with yourprecise case in mind. -- Keir-- Joshua West Systems Engineer Brandeis University http://www.brandeis.edu _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
-- Joshua West Systems Engineer Brandeis University http://www.brandeis.edu _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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