ggml/src/ggml-cuda/cp-async.cuh

// Simplified API for asynchronous data loading.

#include "common.cuh"

// Copies data from global to shared memory, cg == cache global.
// Both the src and dst pointers must be aligned to 16 bit.
// Shared memory uses 32 bit addressing, the pointer is passed as unsigned int.
// Generic pointers can be converted to 32 bit shared memory pointers using __cvta_generic_to_shared.
// Only the 16 bit copy is exposed because 4 and 8 bit copies did not yield performance improvements.
template <int preload>
static __device__ __forceinline__ void cp_async_cg_16(const unsigned int dst, const void * src) {
    static_assert(preload == 0 || preload == 64 || preload == 128 || preload == 256, "bad preload");
#ifdef CP_ASYNC_AVAILABLE
#if CUDART_VERSION >= 11040
    if (preload == 256) {
        asm volatile("cp.async.cg.shared.global.L2::256B [%0], [%1], 16;"
            : : "r"(dst), "l"(src));
    } else if (preload == 128) {
        asm volatile("cp.async.cg.shared.global.L2::128B [%0], [%1], 16;"
            : : "r"(dst), "l"(src));
    } else if (preload == 64) {
        asm volatile("cp.async.cg.shared.global.L2::64B [%0], [%1], 16;"
            : : "r"(dst), "l"(src));
    } else
#endif // CUDART_VERSION >= 11040
    {
        asm volatile("cp.async.cg.shared.global [%0], [%1], 16;"
            : : "r"(dst), "l"(src));
    }
#else
    GGML_UNUSED(dst);
    GGML_UNUSED(src);
    NO_DEVICE_CODE;
#endif // CP_ASYNC_AVAILABLE
}

// Makes each thread wait until its asynchronous data copies are done.
// This does NOT provide any additional synchronization.
// In particular, when copying data with multiple warps a call to __syncthreads will be needed.
static __device__ __forceinline__ void cp_async_wait_all() {
#ifdef CP_ASYNC_AVAILABLE
    asm volatile("cp.async.wait_all;");
#else
    NO_DEVICE_CODE;
#endif // CP_ASYNC_AVAILABLE
}