Linux is generally more efficient with handling many threads. Recent versions have improved use of ARC.
ZFS 2.3 has improved. We’ve actively been looking for bottlenecks and contributing back. The charts here are not NVMe but there are bigger improvements there.
iSCSI and NFS stacks are OS specific. Some sandpapering of these have removed rough edges with integration with ZFS.
TrueNAS middleware is not really in the datapath, but it does impact things like reboot times and management of hundreds of disks. That part has improved dramatically over the last couple of years, but is not evident in these specific charts.
We don’t do performance testing of each component… its too time and resource consuming. We test each release as a whole and look for any regressions or problems.