[Xen-users] Exactly set dom0/U memory, increase vcpu count

[Michal Fiala <fiala@xxxxxxxxxx>]

hallo,

I have updated xen server to

xen-4.2.1-r2
xen-tools-4.2.1-r1
kernel gentoo-sources-3.2.39

I have found 2 problems

1) Can not exactly set dom0, domU memory

I dedicate 4G of memory to dom0 via kernel parameter:

dom0_mem=4G,max:4G dom0_max_vcpus=4 dom0_vcpus_pin

Bud the real total memory is set to 2618M after reboot. I have found
article describing this behavior
(http://wiki.xen.org/wiki/Do%EF%BB%BFm0_Memory_%E2%80%94_Where_It_Has_Not_Gone),
so I have run

echo $((4*1024*1024)) > /sys/devices/system/xen_memory/xen_memory0/target_kb

The total memory was se to 3687M. This is better, but not enough.

I have tested kernel 3.7, there is not such problem. I would like to use
longterm kernel 3.2 so I would like to stay with 3.2.

Similar problem exists with domU, config looks like

kernel = '/etc/xen/kernels/linux-3.2.39-gentoo'
name   = 'test1'
memory = '4000'
maxmem = '12000'
vcpus  = '8'
cpus   = '^0,^1,^2,^3'
extra  = 'elevator=noop gentoo=nodevfs'
root   = '/dev/xvda1 ro'
disk   = [
              'phy:/dev/vg1/test1_root,xvda1,w',
              'phy:/dev/vg1/test1_var,xvda2,w',
         ]
vif    = [
              'mac=00:16:3e:24:11:38,bridge=br0',
         ]

After boot, test1 domain has 3704M total memory (free -m), xm list test1
shows 4000M.

When I increase memory amount via xm mem-set test1 8000, then xm list
test1 really shows 8000M, but domU has 7704M total memory (free -m).

from xend.log
[2013-03-04 18:10:18 4627] DEBUG (XendDomainInfo:1467) Setting memory
target of domain test1 (1) to 8000 MiB.

2) I am not able to increase vcpu count to domU.
After boot domU test1, it has really 8 vcpus, I am able to decrease
vcpus by xm vcpu-set test1 4. Cpus count inside test1 really decreases
to 4. Now I would like to increase vcpu count via xm vcpu-list test1 6,
but unsuccessfully.

rajvir3 configs # xm vcpu-list test1
Name                                ID  VCPU   CPU State   Time(s) CPU
Affinity
test1                                1     0    15   -b-       3.7 12-23
test1                                1     1    23   -b-       2.8 12-23
test1                                1     2    18   -b-       1.2 12-23
test1                                1     3    20   -b-       1.2 12-23
test1                                1     4    16   -b-       1.0 12-23
test1                                1     5    12   -b-       3.5 12-23
test1                                1     6    19   -b-       0.9 12-23
test1                                1     7    14   -b-       0.9 12-23

rajvir3 configs # xm vcpu-set test1 4

rajvir3 configs # xm vcpu-list test1
Name                                ID  VCPU   CPU State   Time(s) CPU
Affinity
test1                                1     0    15   -b-       3.7 12-23
test1                                1     1    23   -b-       2.9 12-23
test1                                1     2    18   -b-       1.3 12-23
test1                                1     3    20   -b-       1.2 12-23
test1                                1     4     -   --p       1.0 12-23
test1                                1     5     -   --p       3.5 12-23
test1                                1     6     -   --p       1.0 12-23
test1                                1     7     -   --p       0.9 12-23

rajvir3 configs # xm vcpu-set test1 6

rajvir3 configs # xm vcpu-list test1
Name                                ID  VCPU   CPU State   Time(s) CPU
Affinity
test1                                1     0    15   -b-       3.8 12-23
test1                                1     1    23   -b-       2.9 12-23
test1                                1     2    18   -b-       1.3 12-23
test1                                1     3    20   -b-       1.3 12-23
test1                                1     4     -   --p       1.0 12-23
test1                                1     5     -   --p       3.5 12-23
test1                                1     6     -   --p       1.0 12-23
test1                                1     7     -   --p       0.9 12-23

from xend.log

[2013-03-04 18:12:58 4627] INFO (XendDomainInfo:1978) Set VCPU count on
domain test1 to 4
[2013-03-04 18:14:51 4627] INFO (XendDomainInfo:1978) Set VCPU count on
domain test1 to 6

I was not able to increase vcpu count also in kernel 3.7.

Where could be the problem?

Thanks

Michal

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