On some Adreno devices (the Retroid Pocket Duo) SELinux hides kgsl's sysfs
nodes from apps, so the HUD showed no GPU % and no GPU clock. Devices whose
nodes are readable keep using them; nothing changes there or on GPUs
without kgsl.
Where the nodes are blocked:
- GPU %: a native reader maps kgsl's memstore read-only (any kgsl client
may) and samples the ringbuffer start/end timestamps once a millisecond
while a HUD is shown. That covers all GPU work, Android's own
composition included.
- Backup for GPU %: an implicit Vulkan layer in the guest
(tools/gpuload) and the compositor time their own GPU work with
timestamp queries. It runs until the memstore stamps are seen moving,
and for the whole session if they never move.
- GPU clock: a small GPU job of our own reads the always-on and RBBM
cycle counters (libgpuclock).
The HUD diagnostics export lists which source each GPU value came from.
tools/gpuload/build.sh takes the Vulkan headers from build_local.sh's NDK
first and keeps NDK paths with spaces intact.
