GPU Performance Analysis and Optimization - GPU Technology ...

Pattern Category 2: Large Inter-thread Stride• Cause:– Successive threads access words at regular distance, distance greater than one word• GPU access words: 1, 2, 4, 8, 16 bytes– Example cases:• Data transpose (warp accessing a column in a row-major data structure)• Cases where some data is accessed in transposed fashion, other isn’t• Issues:– Wasted bandwidth: moves more bytes than needed– Substantially increased latency:• If a warp address pattern requires N transactions, the instruction is issued N times• Symptoms:– Transactions per request much greater than ideal• Remedies:– Full: change data layout, stage accesses via SMEM– Partial: non-caching loads, read-only loads© 2012, NVIDIA56