taskpolicy
execute a program with an altered I/O or scheduling policy or
change settings of already running process

taskpolicy [-d policy] [-g policy] [-c clamp] [-b] [-t thruput_tier] [-l latency_tier] program [arg1 [...]]

taskpolicy [-b|-B] [-t thruput_tier] [-l latency_tier] [-p pid]

Uses setiopolicy_np and setpriority APIs to execute a program with altered I/O or scheduling policies. All children of the specified program inherit these policies.
-d policy Run the program after calling setiopolicy_np with an iotype of IOPOL_TYPE_DISK, a scope of IOPOL_SCOPE_PROCESS, and the specified policy. policy is an integer, or a symbolic string like default or throttle
-g policy Run the program after calling setiopolicy_np with an iotype of IOPOL_TYPE_DISK, a scope of IOPOL_SCOPE_DARWIN_BG, and the specified policy.
-c clamp Run the program using the specified QoS clamp of
utility, background or maintenance
-p pid Change settings for the process
-b Run the program with a priority of PRIO_DARWIN_BG.
-B Move target process out of PRIO_DARWIN_BG.
-t Set throughput tier of the process to thruput_tier.
-l Set latency tier of the process to latency_tier.
SEE setpriority(2), setiopolicy_np(3)

Scope of these AIPs could be IOPOL_SCOPE_PROCESS or IOPOL_SCOPE_THREAD
IOPOL_IMPORTANTunrestricted. critical to system responsiveness. default I/O policy for new threads. (sic)
STANDARDnot the user's current focus. I/Os be delayed slightly
UTILITYshort-running background work. I/Os throttled
THROTTLElong-running I/O intensive background work, backups, search indexing, or file synchronization. I/Os will be throttled
PASSIVEuseful for server type applications. IOs caused directly or indirectly by the I/O requests received from client applications.
Be aware that although IMPORTANT IO may be placed ahead of other IO in the OS queues, commands already sent to the disk cannot be rearranged.