Hi laughingrice,
Some threads access different address in the same bank at the same time, this will generate bank conflicts. All AMD Evergreen GPUs contain a 32K LDS for each compute uint. On high-end GPUs, the LDS contains 32-banks, each bank is four bytes long, and the bank address is determined by bits 6:2 in the adddress. On lower-end GPUs, the LDS contains 16 banks, each bank is still 4 bytes in size, and the bank used is determined by bits 5:2 in the address.
Thank you.