Xen compute is CentOS 6.5, KVM compute node is RHEL 6.5. On the XEN node, I see:

 tm1cldcmpl03 QEMU  32  0   920MB   512MB   2.0GB   0Bytes  0<BR>

On the KVM node I see:

 tm1cldcmpl02 QEMU  32  5   31GB    3GB 2.0GB   55.0GB  5

These are identical HP Proliant DL380 gen8 system with 32 cores and 32gb of memory. I can't launch anything on xen system because it doesn't think it has enough memory to do anything.

Here's not nova compute log excerpt:

2014-06-09 14:51:15.701 3916 INFO oslo.messaging._drivers.impl_qpid [-] Connected to AMQP server on tm1cldctll01:5672<br>
2014-06-09 14:52:03.745 3916 AUDIT nova.compute.resource_tracker [req-f1e977f5-fcb5-4878-8b1f-9c176b825646 None None] Auditing locally available compute resources<br>
2014-06-09 14:52:04.854 3916 AUDIT nova.compute.resource_tracker [req-f1e977f5-fcb5-4878-8b1f-9c176b825646 None None] Free ram (MB): 408<br>
2014-06-09 14:52:04.854 3916 AUDIT nova.compute.resource_tracker [req-f1e977f5-fcb5-4878-8b1f-9c176b825646 None None] Free disk (GB): 2<br>
2014-06-09 14:52:04.855 3916 AUDIT nova.compute.resource_tracker [req-f1e977f5-fcb5-4878-8b1f-9c176b825646 None None] Free VCPUS: 32<br>
2014-06-09 14:52:04.899 3916 INFO nova.compute.resource_tracker [req-f1e977f5-fcb5-4878-8b1f-9c176b825646 None None] Compute_service record updated for tm1cldcmpl03:tm1cldcmpl03<br>
2014-06-09 14:52:12.253 3916 AUDIT nova.compute.resource_tracker [-] Auditing locally available compute resources<br>
2014-06-09 14:52:13.345 3916 AUDIT nova.compute.resource_tracker [-] Free ram (MB): 408<br>
2014-06-09 14:52:13.345 3916 AUDIT nova.compute.resource_tracker [-] Free disk (GB): 2<br>
2014-06-09 14:52:13.345 3916 AUDIT nova.compute.resource_tracker [-] Free VCPUS: 32<br>
2014-06-09 14:52:13.385 3916 INFO nova.compute.resource_tracker [-] Compute_service record updated for tm1cldcmpl03:tm1cldcmpl03<br>

the xl info:

# xl info<br>
host                   : tm1cldcmpl03<br>
release                : 3.10.34-11.el6.centos.alt.x86_64<br>
version                : #1 SMP Fri Mar 28 00:57:43 UTC 2014<br>
machine                : x86_64<br>
nr_cpus                : 32<br>
max_cpu_id             : 63<br>
nr_nodes               : 2<br>
cores_per_socket       : 8<br>
threads_per_core       : 2<br>
cpu_mhz                : 2893<br>
hw_caps                : bfebfbff:2c100800:00000000:00003f40:17bee3ff:00000000:00000001:00000000<br>
virt_caps              : hvm hvm_directio<br>
total_memory           : 32733<br>
free_memory            : 31280<br>
sharing_freed_memory   : 0<br>
sharing_used_memory    : 0<br>
free_cpus              : 0<br>
xen_major              : 4<br>
xen_minor              : 2<br>
xen_extra              : .4-30.el6<br>
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p hvm-3.0-x86_64<br>
xen_scheduler          : credit<br>
xen_pagesize           : 4096<br>
platform_params        : virt_start=0xffff800000000000<br>
xen_changeset          : unavailable<br>
xen_commandline        : dom0_mem=1024M,max:1024M loglvl=all guest_loglvl=all<br>
cc_compiler            : gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-4)<br>
cc_compile_by          : mockbuild<br>
cc_compile_domain      : centos.org<br>
cc_compile_date        : Thu Mar 27 23:03:24 UTC 2014<br>
xend_config_format     : 4<br>

And why would the # of vcpus in use be different?