diff --git a/ggml/src/ggml-backend.cpp b/ggml/src/ggml-backend.cpp index 1b59924b8c..cf5548964f 100644 --- a/ggml/src/ggml-backend.cpp +++ b/ggml/src/ggml-backend.cpp @@ -736,6 +736,38 @@ struct ggml_backend_sched { int debug_prev_graph_size; }; +static void ggml_backend_synchronize_if_required(ggml_backend_t current_backend, bool backend_implicitly_synced) { + + if (backend_implicitly_synced) { + return; + } + + ggml_backend_synchronize(current_backend); +} + +static bool ggml_backend_implicitly_synced(ggml_backend_t current_backend) { + /* + * Some backends have implicit synchronization mechanisms, which allows several parallel asynchronous memory copies without data races. + * An example for that is the CUDA backend with the CUDA stream. + * For these backends, we can skip costly explicit synchronizations during compute split scheduling. + */ + + static bool disable_scheduler_sync_opt = (getenv("GGML_SCHED_DISABLE_SYNC_OPT") != nullptr); + + if (disable_scheduler_sync_opt) { + return false; + } + + // To not change any APIs or change what ggml-base links to, we can only detect backends by string matching + auto backend_name = ggml_backend_name(current_backend); + if (strncmp(backend_name, "CUDA", 4) == 0) { + return true; + } + + // sync other backends to ensure correctness + return false; +} + #define hash_id(tensor) ggml_hash_find_or_insert(&sched->hash_set, tensor) #define tensor_backend_id(tensor) sched->hv_tensor_backend_ids[hash_id(tensor)] #define tensor_id_copy(id, backend_id, copy_id) sched->hv_tensor_copies[(id) * sched->n_backends * sched->n_copies + (backend_id) * sched->n_copies + (copy_id)] @@ -1452,6 +1484,8 @@ static enum ggml_status ggml_backend_sched_compute_splits(ggml_backend_sched_t s struct ggml_backend_sched_split * split = &splits[split_id]; int split_backend_id = split->backend_id; ggml_backend_t split_backend = sched->backends[split_backend_id]; + // some backends can avoid costly syncs between async copies + bool backend_implicitly_synced = ggml_backend_implicitly_synced(split_backend); // copy the input tensors to the split backend for (int input_id = 0; input_id < split->n_inputs; input_id++) { @@ -1464,15 +1498,16 @@ static enum ggml_status ggml_backend_sched_compute_splits(ggml_backend_sched_t s if (sched->events[split_backend_id][sched->cur_copy] != NULL) { ggml_backend_event_synchronize(sched->events[split_backend_id][sched->cur_copy]); } else { - ggml_backend_synchronize(split_backend); + ggml_backend_synchronize_if_required(split_backend, backend_implicitly_synced); } - ggml_backend_tensor_copy(input, input_cpy); + ggml_backend_tensor_copy_async(input_backend, split_backend, input, input_cpy); + ggml_backend_synchronize_if_required(split_backend, backend_implicitly_synced); } else { // wait for the split backend to finish using the input before overwriting it if (sched->events[split_backend_id][sched->cur_copy] != NULL) { ggml_backend_event_wait(split_backend, sched->events[split_backend_id][sched->cur_copy]); } else { - ggml_backend_synchronize(split_backend); + ggml_backend_synchronize_if_required(split_backend, backend_implicitly_synced); } // when offloading MoE weights, we can reduce the amount of data copied by copying only the experts that are used diff --git a/ggml/src/ggml-cuda/ggml-cuda.cu b/ggml/src/ggml-cuda/ggml-cuda.cu index 84eccea3f7..1964ffd748 100644 --- a/ggml/src/ggml-cuda/ggml-cuda.cu +++ b/ggml/src/ggml-cuda/ggml-cuda.cu @@ -2780,11 +2780,14 @@ static bool ggml_backend_cuda_cpy_tensor_async(ggml_backend_t backend_src, ggml_ ggml_backend_buffer_t buf_src = src->view_src ? src->view_src->buffer : src->buffer; ggml_backend_buffer_t buf_dst = dst->view_src ? dst->view_src->buffer : dst->buffer; - if (!ggml_backend_is_cuda(backend_src) || !ggml_backend_is_cuda(backend_dst)) { + //enables async copies from CPU to CUDA, instead of only CUDA-to-CUDA + bool copy_from_host = ggml_backend_buffer_is_host(src->buffer); + + if (!(copy_from_host || ggml_backend_is_cuda(backend_src)) || !ggml_backend_is_cuda(backend_dst)) { return false; } - if (!ggml_backend_buffer_is_cuda(src->buffer) || !ggml_backend_buffer_is_cuda(dst->buffer)) { + if (!(copy_from_host || ggml_backend_buffer_is_cuda(src->buffer)) || !ggml_backend_buffer_is_cuda(dst->buffer)) { return false; } @@ -2795,14 +2798,19 @@ static bool ggml_backend_cuda_cpy_tensor_async(ggml_backend_t backend_src, ggml_ ggml_backend_cuda_buffer_context * buf_ctx_src = (ggml_backend_cuda_buffer_context *)buf_src->context; ggml_backend_cuda_buffer_context * buf_ctx_dst = (ggml_backend_cuda_buffer_context *)buf_dst->context; - if (cuda_ctx_src->device != buf_ctx_src->device || cuda_ctx_dst->device != buf_ctx_dst->device) { + if (!copy_from_host && (cuda_ctx_src->device != buf_ctx_src->device || cuda_ctx_dst->device != buf_ctx_dst->device)) { #ifndef NDEBUG GGML_LOG_DEBUG("%s: backend and buffer devices do not match\n", __func__); #endif return false; } - if (backend_src != backend_dst) { + if (copy_from_host) { + if (!cuda_ctx_dst->stream()) { + return false; + } + CUDA_CHECK(cudaMemcpyAsync(dst->data, src->data, ggml_nbytes(dst), cudaMemcpyHostToDevice, cuda_ctx_dst->stream())); + } else if (backend_src != backend_dst) { // copy on src stream if (cuda_ctx_src->device == cuda_ctx_dst->device) { CUDA_CHECK(cudaMemcpyAsync(dst->data, src->data, ggml_nbytes(dst), cudaMemcpyDeviceToDevice, cuda_ctx_src->stream()));