[Xen-users] Strange calculation of free_memory

[Alexander Kobernik <akobernik@xxxxxxxxx>]

Hi everybody,

there is physical box with 32GB of RAM installed on it.

DomU domains aren't not launched yet. Here's output of 'xm list' command:

Name     ID  Mem VCPUs  State   Time(s)
Domain-0  0  512     8 r----- 107900.3

So, there's only Dom0 there. Here's output of 'free -m' command:

             total used free shared buffers cached
Mem:           512  378  133      0      53     90
-/+ buffers/cache:  234  277
Swap:         2047    0 2047

Thus free/available memory (for DomUs) should be equal to something like:

32GB - 512MB = 32256MB = 33030144KB

However, according to Xen, there are about 31791MB of free memory only.

Here's output of 'xm info' command:

host               : xxx
release            : 2.6.18-92.1.6.el5xen
version            : #1 SMP Wed Jun 25 14:13:10 EDT 2008
machine            : x86_64
nr_cpus            : 8
nr_nodes           : 1
cores_per_socket   : 4
threads_per_core   : 1
cpu_mhz            : 2660
hw_caps            : bfebfbff:20100800:00000000:00000140:040ce3bd:00000000:00000001:00000000
virt_caps          : hvm
total_memory       : 32762
free_memory        : 31791
node_to_cpu        : node0:0-7
node_to_memory     : node0:31791
xen_major          : 3
xen_minor          : 3
xen_extra          : .0
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 
xen_scheduler      : credit
xen_pagesize       : 4096
platform_params    : virt_start=0xffff800000000000
xen_changeset      : unavailable
cc_compiler        : gcc version 4.1.2 20071124 (Red Hat 4.1.2-42)
cc_compile_by      : root
cc_compile_domain  : xxx
cc_compile_date    : Tue Sep  9 20:18:14 CEST 2008
xend_config_format : 4

Here's reduced output of 'xm top' command:

xentop - 12:51:59   Xen 3.3.0
1 domains: 1 running, 0 blocked, 0 paused, 0 crashed, 0 dying, 0 shutdown
Mem: 33549248k total, 995128k used, 32554120k free    CPUs: 8 @ 2660MHz

NAME  STATE   CPU(sec) CPU(%)     MEM(k) MEM(%)  MAXMEM(k) MAXMEM(%)
Domain-0 -----r     107963    0.0     524288    1.6   no limit       n/a


So, could someone explain who allocated/cached 465MB (32256MB - 31791MB) of RAM?

-- 
Alexander
_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users