xen-balloon and 5.10.70

[Henrik Riomar <rio@xxxxxxxxx>]

Hi,

Running 5.10.70 on a dom0 shows 100% load on one core for the
xen-balloon kernel thread (was a workqueue before 5.10.70).

I have upgraded two dom0's to 5.10.70 and both of them shows this issue.

Xen version is 4.15.1.

To trigger the problem:
 dom_mem=3000M,max:3000M

Does not trigger the problem:
 dom_mem=3000M

(the other system with the issue has "dom0_mem=4096M,max:4096M")

/etc/xl/xl.conf:
 #autoballon="auto" 
 or
 autoballon="off"
 or 
 autoballon="on"

does not matter, in trigging the problem (i.e. autoballon="off", still
gets [xen-ballon] to hog down one core).

Can not see the problem before starting the first domU, and shutting
down all domUs stops xen-balloon to hog the core.

Workaround in a running system is to lower
 /sys/devices/system/xen_memory/xen_memory0/target_kb.

With max:3000M this was 3072000 (kb), and just lowering it to 3069952
(i.e. by 2 meg) "solved" the issue, and stopped the fan in my laptop :-)

/ Henrik