Ping. Ceasr
On 06/20/2018 02:59 PM, Cesar Philippidis wrote: > At present, the nvptx libgomp plugin does not take into account the > amount of shared resources on GPUs (mostly shared-memory are register > usage) when selecting the default num_gangs and num_workers. In certain > situations, an OpenACC offloaded function can fail to launch if the GPU > does not have sufficient shared resources to accommodate all of the > threads in a CUDA block. This typically manifests when a PTX function > uses a lot of registers and num_workers is set too large, although it > can also happen if the shared-memory has been exhausted by the threads > in a vector. > > This patch resolves that issue by adjusting num_workers based the amount > of shared resources used by each threads. If worker parallelism has been > requested, libgomp will spawn as many workers as possible up to 32. > Without this patch, libgomp would always default to launching 32 workers > when worker parallelism is used. > > Besides for the worker parallelism, this patch also includes some > heuristics on selecting num_gangs. Before, the plugin would launch two > gangs per GPU multiprocessor. Now it follows the formula contained in > the "CUDA Occupancy Calculator" spreadsheet that's distributed with CUDA. > > Is this patch OK for trunk? > > Thanks, > Cesar >
