Calculating memory used by Xen hypervisor

SUSE Linux Enterprise Server SLES Virtualization
1

According to ‘TID 3559698 - XEN Dom0 becomes unresponsive when shutting
down a domU virtual machine’
(http://www.novell.com/support/php/search.do?cmd=displayKC&docType=kc&externalId=3559698&sliceId=1&docTypeID=DT_TID_1_1&dialogID=275099292&stateId=0%200%20275097402),
I should be able to calculate approximately how much memory is
used/needed by the Xen hypervisor.> it is possible to get a good idea of how much is required by booting XEN[color=blue]

in the default configuration (all available memory assigned to dom0).
In this configuration, the total system memory minus the amount of
memory assigned to dom0 equals the amount required by the hypervisor.[/color]
With -only Dom0 running-, I see:

Code:

server:~ # xm info
host : server
release : 2.6.32.45-0.3-xen
version : #1 SMP 2011-08-22 10:12:58 +0200
machine : x86_64

total_memory : 6143
free_memory : 3592
max_free_memory : 5557
max_para_memory : 5553
max_hvm_memory : 5532

According to the TID> The amount of memory needed by the hypervisor, domain0, and each domU[color=blue]

varies based on machine specifications, type of VM, etc. Therefore,
there are no fixed values that can be assigned to any of those
variables. However, ‘xm info’ can provide a view into the current state
of the system. There are 5 fields in the list that provide information
about the memory status:

total_memory : 6143 # Total RAM available to the system
free_memory : 3592 # Free RAM (not in use by hypervisor, dom0, or any
domU)
max_free_memory : 5557 # Maximum value possible for"free_memory" after
ballooning dom0
max_para_memory : 5553 # Maximum amount of memory that could be
assigned to a new pv guest
max_hvm_memory : 5532 # Maximum amount of memory that could be assigned
to a new fv guest
[/color]
Dom0 has 2477 MB of memory assigned as can be seen here:

Code:

server:~ # xm list -l Domain-0
(domain
(domid 0)
(cpu_weight 256)
(cpu_cap 0)
(pool_name Pool-0)
(bootloader )
(vcpus 4)
(cpus ((0 1 2 3) (0 1 2 3) (0 1 2 3) (0 1 2 3)))
(on_poweroff destroy)
(description )
(on_crash restart)
(uuid 00000000-0000-0000-0000-000000000000)
(bootloader_args )
(name Domain-0)
(on_reboot restart)
(maxmem 16777215)
(memory 2477)
(shadow_memory 0)
(features )
(on_xend_start ignore)
(on_xend_stop ignore)
(cpu_time 147464.486225)
(online_vcpus 4)
(image (linux (kernel ) (superpages 0) (nomigrate 0) (tsc_mode 0)))
(status 2)
(state r-----)
)

I find it difficult to believe that the hypervisor is only using 74
MB!!!
6143-2477-3592 = 74 MB

The TID suggests that I need to make -all memory- available to Dom0 for
this calculation to work. I don’t know where the 2477 MB limit is set
and I don’t see how I can change the Dom0 settings as I would for a
DomU.

Any ideas?

–
Kevin Boyle
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