Why xen for DomU allocated and actually consumed memory differ?

On the hypervisor

xl list
Name ID Mem VCPUs State Time(s)
Domain-0 0 12594 12 r----- 1281771.4
vr.local 145 1536 1-b---- 111054.9


On the guest machine

cat /proc/meminfo | grep MemTotal:
MemTotal: 1314188 kB


free
 total used free shared buff/cache available
Mem: 1314188 510668 49488 459828 754032 296892
Swap: 1048572 159060 889512


Why is the memory value are so different? 1536 − 1283 = 253, i.e., the difference in 253 Mb
Xen version 4.4.1
July 9th 19 at 13:12
More answers about "Why xen for DomU allocated and actually consumed memory differ?"
2 answers
July 9th 19 at 13:14
Solution
After a while he decided to deal with the issue, I guess I forgot to say that the OS DomU CentOS7.

In General, all simply and xen got nothing to do with the whole thing in the kdump kernel, it reserves memory:

Reserving 161MB of memory at 720MB for crashkernel

The output of cat /proc/cmdline and free c kdump:

root=/dev/mapper/centos_t-root ro rd.lvm.lv=centos_t/root crashkernel=auto rd.lvm.lv=centos_t/swap LANG=en_US.UTF-8 systemd.log_level=debug systemd.log_target=kmsg
Mem: 1315164 107800 1102036 16580 105328 1164352


And without it:

root=/dev/mapper/centos_t-root ro rd.lvm.lv=centos_t/root rd.lvm.lv=centos_t/swap LANG=en_US.UTF-8 systemd.log_level=debug systemd.log_target=kmsg
Mem: 1480028 107620 1267208 16580 105200 1328432


As you can see the memory increased.
The same goes for the needs of the kernel.
July 9th 19 at 13:16
Maybe it's the memory allocated for the video?
No, it's a linux server, why did he have so much VRAM. - nia_Schoen commented on July 9th 19 at 13:19
: well, you never know, it might even shadow_memory - Concepcion.Walsh commented on July 9th 19 at 13:22

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