LXD 6.1 Released With Automatic Core Pinning Load Balancing, Fixes Hosts With 64+ CPU Cores

Canonical today released LXD 6.1 as the newest version of this Ubuntu-focused solution for managing virtual machines (VMs) and containers.

LXD 6.1 represents the first feature release in the new LXD 6.x series. LXD 6.1 adds support for automatic IP allocation for OVN network forwards and load balancers, VM automatic core pinning load balancing, drops the "trust password" feature for better security, drops ARMHF support for Ceph, bumps the minimum Go language version required, and various other changes.

The automatic core pinning load balancing feature should be helpful to some systems but for Intel Core hybrid systems this may cause issue. The LXD 6.1 release announcement explains:

"Virtual machines that don’t explicitly specify the CPU cores to use will now have their QEMU processes automatically pinned to load balanced CPU cores by LXD’s instance scheduler. This mirrors the behaviour that LXD container processes follow. LXD’s scheduler will periodically rebalance the CPU pinning configuration when instances are added, modified or removed. This change has been added to make VM performance more predictable for latency sensitive applications.

Note: On systems that have mixed performance and efficiency cores (P+E) you may find that VM performance is decreased due to the way LXD now pins some of the VM’s vCPUs to efficiency cores rather than letting the Linux scheduler dynamically schedule them. You can use the explicit CPU pinning feature if needed to avoid this."

LXD 6.1 also fixes support for running virtual machines on hosts with more thna 64 CPU cores present... There was an "issue" with LCD that it couldn't start VMs on hosts with more thna 64 CPUs but is now resolved. LXD continues to have a limit of 256 vCPUs for starting VM guests, but this was a separate issue that LXD would run into troubles if the host had more than 64 CPU cores... Which is increasingly problematic with high core count AMD EPYC server processors around for years, Intel Xeon 6 with Sierra Forest driving core counts higher, Ampere's high core count ARM servers, etc.

More details on all of the changes with LXD 6.1 via the Ubuntu Discourse.