[xapi] high cpu utilization after migrationg to 7.1 / 7.2

We moved from Xenserver 6.5 to Xenserver 7.1 and 7.2

After the upgrade we see high response times from xenapi for any kind of command like add vif, mount ISO, start vms, and others.

On the server i can see a very high utilization of xapi process on pools with more than 300 vms:

root     13198  132 18.5 10008240 1122792 ?    SLsl 09:04  55:09 /opt/xensource/bin/xapi -nowatchdog -writereadyfile /var/run/xapi_startup.cookie -writeinitcomplete /var/run/xapi_init_complete.cookie

On another pool not upgraded, the cpu utilization of xenapi is very low and everything works fine:

root      7426  1.9 46.6 3631856 2803476 ?     SLsl  2016 8040:04 /opt/xensource/bin/xapi -nowatchdog -writereadyfile /var/run/xapi_startup.cookie -writeinitcomplete /var/run/xapi_init_complete.cookie

This occurs on ALL of our pools upgraded to 7.1/7.2.

Thanks