Re: [Xen-users] Re: [Xen-devel] Xen - Guest memory allocation

[weiming <zephyr.zhao@xxxxxxxxx>]

by default, dom0 gets all the available memory (usable physical memory - xen hypervisor). Then, when domU starts up, xen will decrease  dom0's allocation via ballooning and allocate them to domU.

Do you want to specify the exact physical memory address space used by domU?

On Mon, Jun 16, 2008 at 2:37 PM, dinesh chandrasekaran <dinesh_chan8@xxxxxxxxxxx> wrote:

Yes, ofcourse dom0 can see this range.

But all the domUs memory has to fall in this restricted memory range (as specified by mypci_usabe)?

for example,
If I start three virtual machines, say VM1, VM2, VM3 with 64MB memory each,
how could I make sure that, the total 192MB for three VMs lie somewhere in mypci_usable range only and not anywhere else.

Thanks,
Dinesh C

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Date: Thu, 12 Jun 2008 22:37:17 -0400

From: zephyr.zhao@xxxxxxxxx
To: dinesh_chan8@xxxxxxxxxxx

Subject: Re: [Xen-users] Re: [Xen-devel] Xen - Guest memory allocation

CC: xen-devel@xxxxxxxxxxxxxxxxxxx; xen-users@xxxxxxxxxxxxxxxxxxx

Can dom0 address the whole memory space if no other domU running? If so, it can freely allocate memory to other guests.

On Thu, Jun 12, 2008 at 3:34 PM, dinesh chandrasekaran <dinesh_chan8@xxxxxxxxxxx> wrote:

Thanks Weiming,

                            But did the same by editing the e820.c. That is, after xen boots up, if I type "xm dmesg" I could find my output which is
(000000000fff000000 - 00000000ffffffff (mypci_usable)).

I couldn't find the exact place in xen source where the memory allocation for DomU guests are performed.

Now how can I make XEN use the above (mypci_usable) memory range to allocate memory for all its DomU guests.

Thanks in advance
Dinesh C

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Date: Fri, 6 Jun 2008 15:12:49 -0400
From: zephyr.zhao@xxxxxxxxx
To: dinesh_chan8@xxxxxxxxxxx
CC: xen-devel@xxxxxxxxxxxxxxxxxxx; xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Re: [Xen-devel] Xen - Guest memory allocation

I'm not very sure about your problem. Can the Hypervisor address the whole 5GB space? If yes, it can then allocate any of them to guests.

Or you can modify the "start info" passed to Guest OS. You can change the page_nr, a machine-PFN translation table to enable the guest to address the memory space that you want. It's weird.

On Fri, Jun 6, 2008 at 2:57 PM, dinesh chandrasekaran <dinesh_chan8@xxxxxxxxxxx> wrote:

YES.

        But if I want to add memory of type E820_USABLE to xen memory map during boot up (as per xen/e820.c) where the memory to be added lies behind a PCI device?

For ex,
If a PCI device reports it has 1GB of memory behind it.
And XEN has identified th RAM memory to be 4GB.

How can the PCI - 1GB can be added as usable memory to XEN's memory pool to get a cumulative size of 5GB;
 
thanks,
Dinesh C

On Fri, Jun 6, 2008 at 3:00 PM, Weiming wrote:

AFAIK, In para virtualization, when guest boots, it reads the memory layout from a special page (start info page) instead of from bios.
If your guest os is a PV Linux, you can check its source code (e.g. start_kernel(), etc.)

Thanks,
Weiming

On Fri, Jun 6, 2008 at 2:00 PM, dinesh chandrasekaran <dinesh_chan8@xxxxxxxxxxx> wrote:

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