@darkbeldin Okay thanks
I did test this and it worked.

@darkbeldin
Okay
Did more tests
Started on host1 normal speed
migrate to host2
make the test got lower speed
restart vm
make the test on host2
Got normal speed
migrate to host1
make the test got lower speed
migrate to host2 normal speed

so it seems to be something that happens after first migrating to another host

I have a third exactly the same pc i should test install on it
and see what happens if i move vm to host3 after moving to host2
but I have to do it tomorrow, I do not have time now.

@darkbeldin
Hello
I installed clean new xcp-ng 8.2 on 2 identical PCs name host1 and host2 then updated to latest "yum update"
then install a virtual machine ubuntu 20.04 with static 4GB of memory and with guest tools.
Install redis-server
Then I did the test
on host1
root@ramtest:/home/andreas# redis-benchmark -r 1000000 -n 2000000 -t get,set,lpush,lpop -P 16 -q
SET: 243368.20 requests per second
GET: 261917.23 requests per second
LPUSH: 257499.67 requests per second
LPOP: 264830.50 requests per second

Then migrate to host2 got lower speed
root@ramtest:/home/andreas# redis-benchmark -r 1000000 -n 2000000 -t get,set,lpush,lpop -P 16 -q
SET: 92055.60 requests per second
GET: 95297.09 requests per second
LPUSH: 95570.31 requests per second
LPOP: 95401.64 requests per second

Then back to host1 got almost the same speed
root@ramtest:/home/andreas# redis-benchmark -r 1000000 -n 2000000 -t get,set,lpush,lpop -P 16 -q
SET: 238010.23 requests per second
GET: 253100.48 requests per second
LPUSH: 259100.92 requests per second
LPOP: 259134.50 requests per second

@darkbeldin
Okay Thanks

@olivierlambert
Sorry to disturb you.
Okay just to verify that there was nothing wrong with the physical servers.
So I took 2 identical PCs and installed clean new xcp-ng 8.2
then install a virtual machine with static 4GB of memory and with guest tools.
Install redis and ran the test
then migrated VM to other pc and ran the test and the speed was half.
Took out the result before and after attached the files.

1.Before migration.txt
2.After migration.txt

@olivierlambert
Okay thanks
and happy New Year

@olivierlambert
no this change from this
memory-actual ( RO): 6442455040
to this
memory-actual ( RO): 6442450944

and its below but they probably have no significance
start-time
console-uuids
dom-id
VCPUs-utilisation
guest-metrics-last-updated

@olivierlambert
Okay find a value that is different
the test is done on the new VM which has 6 GIB in Ram
This is the value before migration
memory-target ( RO): 0
after migration
memory-target ( RO): 6442450944
and after reboot of VM
memory-target ( RO): 0

@olivierlambert XAPI records this is a bit beyond my knowledge.
I tried to make a brand new VM Ubuntu 20.04 server
just to see so it was not the virtual machine it was wrong in but
unfortunately the same result again.

@olivierlambert Yes, but the problem remains
how can you troubleshoot this or is it in xcp-ng?

@olivierlambert
I have set it to this

Static: 512 MiB/32 GiB
Dynamic: 32 GiB/32 GiB

could not change static value

okay did a migration again
but unfortunately the same result

Before migration

#redis-benchmark -r 1000000 -n 2000000 -t get,set,lpush,lpop -P 16 -q
SET: 223363.84 requests per second
GET: 235793.44 requests per second
LPUSH: 247954.38 requests per second
LPOP: 251572.33 requests per second

After migration

#redis-benchmark -r 1000000 -n 2000000 -t get,set,lpush,lpop -P 16 -q
SET: 111844.31 requests per second
GET: 118119.54 requests per second
LPUSH: 116083.34 requests per second
LPOP: 116795.14 requests per second

After reboot off VM on the second server

#redis-benchmark -r 1000000 -n 2000000 -t get,set,lpush,lpop -P 16 -q
SET: 244468.91 requests per second
GET: 254647.31 requests per second
LPUSH: 261848.66 requests per second
LPOP: 261574.69 requests per second

@olivierlambert no it says

Static: 512 MiB / 32 GiB
Dynamic: 1 GiB / 32 GiB

should I change to this to make it static

Static: 32 GIB / 32 GiB
Dynamic: 32 GiB / 32 GiB

because I do not see where I can delete Dynamic

@olivierlambert Okay I'll try it but where do I see if it has dynamic memory
i xen Orchestra?
I have previously used xcp-ng center.

Run latest xcp-ng 8.2
Memory half as fast after migration of vm.

Have 3 exactly the same servers.
I have a VM web server that uses redis
and if i run a memory test and then migrate the VM to another server, it's half as fast.
if I migrate back to the same server, it's still half as fast.
but if I restart the VM, the speed is as it should be again.

See speed test below

#redis-benchmark -r 1000000 -n 2000000 -t get,set,lpush,lpop -P 16 -q
SET: 227401.94 requests per second
GET: 258431.33 requests per second
LPUSH: 254291.17 requests per second
LPOP: 263192.53 requests per second

after migrating to another server

#redis-benchmark -r 1000000 -n 2000000 -t get,set,lpush,lpop -P 16 -q
SET: 100065.05 requests per second
GET: 111944.48 requests per second
LPUSH: 114129.20 requests per second
LPOP: 112549.23 requests per second

after migrating to the first server and restarting the vm

#redis-benchmark -r 1000000 -n 2000000 -t get,set,lpush,lpop -P 16 -q
SET: 218245.31 requests per second
GET: 239721.91 requests per second
LPUSH: 261643.11 requests per second
LPOP: 261506.28 requests per second

Wonder if anyone else has had this problem and knows the cause or has a solution.