Short VM freeze when migrating to another host

[robyt]

@nikade
in VM (linux) with a free i see 94 gb of total memory

[andrewperry]

@nikade thanks for the ideas of where to look!

In my case we're testing and just have a 1Gb link between these hosts, which is what I was putting it down to.

This particular VM is a freshly migrated PV from Debian Xen with:

Memory limits (min/max)
Static: 16 MiB/16 GiB
Dynamic: 8 GiB/16 GiB

Could that Dynamic setting be the problem because as I recall it reduces the VM to 8 on migrate, so when doing the migrate perhaps 8 isn't enough for the VM?

I will try changing it to 16/16 and see if that has any noticeable impact. Thanks!

[olivierlambert]

Yes that's very likely.

[nikade]

@andrewperry yeah try set it 16/16Gb instead, it will probably do some magic

[robyt]

@olivierlambert hi, today i've upgraded my host..
The big VM frozen for ~7 minutes, is a big vm (96 gbram and 32 cpu) but 7 minutes is a very long time (for customer!)
i've setting 96/06 in dynamic: is a normal time?

[olivierlambert]

Can you provide more details? 96/96 in dynamic? Just doing live migration or suspending the VM?

[robyt]

@olivierlambert live migration, the vm is very important (today, in christmas holyday, i've received some phone calls for 7 minutes of freeze..)

[olivierlambert]

The topology looks insane Also, a live migration shouldn't make the VM inaccessible for more than few seconds, except if there is a LOT of memory pages changes, at a pace that is close to the transfer speed.

[robyt]

@olivierlambert ops.. why the best topology?

[olivierlambert]

IIRC, just remove it (small cross) so it should use something default