Mathieu's (patch author) main motivation was removing atomic operation from the LTTng userspace tracer's hot path. In that case, the per-cpu data is the 'reser

Mathieu's (patch author) main motivation was removing atomic operation from the LTTng userspace tracer's hot path. In that case, the per-cpu data is the 'reserve' and 'commit' counters that must be updated when the tracer saves an event to the per-CPU buffers. Other uses that I'm aware of include memory allocators that maintain per-CPU arenas.