Blocking userfaultfd() kernel-fault handling

Posted May 9, 2020 4:58 UTC (Sat) by wahern (subscriber, #37304)
In reply to: Blocking userfaultfd() kernel-fault handling by Cyberax
Parent article: Blocking userfaultfd() kernel-fault handling

AWS doesn't support live migration. Live migration is useful, but not for cloud computing, where state is kept outside the node. It's useful for traditional architectures where state is maintained on the node, with only backups (hopefully!) elsewhere. Not just useful but critical, because you're packing more work on the same piece of hardware, so reboots are more disruptive than with dedicated hardware.

Blocking userfaultfd() kernel-fault handling

Posted May 9, 2020 5:02 UTC (Sat) by Cyberax (✭ supporter ✭, #52523) [Link] (2 responses)

> AWS doesn't support live migration.
It actually does behind the scenes with T2 and T3 instances.

Live migration is very useful to move client software out of a failing node. So really this makes sense only for large cloud providers.

Blocking userfaultfd() kernel-fault handling

Posted May 9, 2020 7:52 UTC (Sat) by wahern (subscriber, #37304) [Link] (1 responses)

Interesting. Any sources which I could share? All I could find in a quick Google search is an HN comment, "T2 and T3 use live migration to get around this, but it's not public knowledge." https://news.ycombinator.com/item?id=17815806

Blocking userfaultfd() kernel-fault handling

Posted May 9, 2020 15:59 UTC (Sat) by Cyberax (✭ supporter ✭, #52523) [Link]

I worked at Amazon, but I've heard about T2/T3 migration publicaly at AWS re:Invent multiple times. These instance types are severely oversubscribed and migration is used to balance the load.