set_native_priority used pthread_setschedparam with sched_priority. Android
threads run under SCHED_OTHER, where sched_priority must be zero and
sched_get_priority_max returns zero, so the call succeeded and changed nothing.
The RSX thread asks for a boost when it starts and was still measured at nice 0,
taking about 5300 involuntary preemptions a second, roughly 130 per frame, from
the PPU, SPU and audio threads sharing its cores. It is the thread everything
else waits on.
Under SCHED_OTHER the scheduler weights by nice, which setpriority does set, and
Android gives apps enough RLIMIT_NICE headroom to go negative for their own
threads. Applies -8 for a raise and +8 for a drop, and warns rather than fails
if the headroom is not there.
Modest on purpose: a hint to be scheduled ahead of the other emulator threads,
not a bid to starve them.
jpolo1224
ab3fcd735d