The CAM layer in DragonFly has had its big lock removed/been marked MPSAFE, so you will notice a performance increase when using multiple disks. (assuming you aren’t throughput-limited, of course.)
A running description of activity related to DragonFly BSD.
How much of DragonFlyBSD isn’t MPSAFE yet?
“not much” I think there’s some parts where it doesn’t matter much – ttys, I think? It may be a question of impact over completeness.
This change doesn’t make all of CAM MPSAFE (most of CAM already was); it removes the implicit MPLOCK around CAM I/O completions SWIs. This will only improve performance when CAM completions were contending on the MPLOCK with other non-MPSAFE subsystems.