CpuTopology::Get and Pin did nothing off Windows, so on a hybrid CPU the
queue workers, the draw front end and the presenter ran wherever the
scheduler put them. On a Linux kernel that reports the same capacity for
every CPU, those threads spent part of each frame on the efficiency cores.
Get now reads the process affinity with sched_getaffinity and the core
classes from /sys/devices/cpu_core/cpus and /sys/devices/cpu_atom/cpus, and
Pin restricts the calling thread with pthread_setaffinity_np. A CPU is
hybrid only when both lists exist and are disjoint, so non-hybrid CPUs are
never pinned. On Linux the workers are pinned to the performance cores of
a hybrid CPU by default; APS5_NO_WORKER_AFFINITY=1 leaves them free.
Windows keeps the APS5_WORKER_AFFINITY=1 opt-in, and
APS5_WORKER_AFFINITY_MASK=<hex> still picks the cores on any platform.
PPSA21564 on a hybrid CPU, pinned against unpinned (2 runs each): title
46.7 to 49.0 fps, menu 45.4 to 47.7, intro level 37.2 to 41.3 (space) and
31.7 to 37.6 (ships). Hub descent 6.56 to 7.92 fps (3 runs each).
Kikoarl
Dean Galvin