Remove the low-latency usage flag

csrc/deep_ep.cpp

@@ -78,13 +78,6 @@ Buffer::Buffer(int rank, int num_ranks, int64_t num_nvl_bytes, int64_t num_rdma_
         CUDA_CHECK(cudaHostGetDevicePointer(&moe_recv_rdma_counter_mapped, const_cast<int*>(moe_recv_rdma_counter), 0));
         *moe_recv_rdma_counter = -1;
     }
-
-    // Low-latency kernels' usage flag
-    if (low_latency_mode) {
-        CUDA_CHECK(cudaMallocHost(&low_latency_usage_flag, sizeof(int), cudaHostAllocMapped));
-        CUDA_CHECK(cudaHostGetDevicePointer(&low_latency_usage_flag_mapped, const_cast<int*>(low_latency_usage_flag), 0));
-        *low_latency_usage_flag = 0;
-    }
 }
 
 Buffer::~Buffer() noexcept(false) {
@@ -1028,16 +1021,6 @@ Buffer::internode_combine(const torch::Tensor& x, const std::optional<torch::Ten
 #endif
 }
 
-uint64_t Buffer::get_low_latency_usage_flag() const {
-#ifndef DISABLE_NVSHMEM
-    EP_HOST_ASSERT(low_latency_usage_flag != nullptr);
-    return reinterpret_cast<uint64_t>(low_latency_usage_flag);
-#else
-    EP_HOST_ASSERT(false and "NVSHMEM is disable during compilation");
-    return 0;
-#endif
-}
-
 void Buffer::clean_low_latency_buffer(int num_max_dispatch_tokens_per_rank, int hidden, int num_experts) {
 #ifndef DISABLE_NVSHMEM
     EP_HOST_ASSERT(low_latency_mode);
@@ -1143,9 +1126,8 @@ Buffer::low_latency_dispatch(const torch::Tensor& x, const torch::Tensor& topk_i
                                num_tokens, hidden, num_max_dispatch_tokens_per_rank,
                                num_topk, num_experts, rank, num_ranks,
                                use_fp8, round_scale, use_ue8m0,
-                               workspace, low_latency_usage_flag_mapped,
+                               workspace, num_device_sms,
-                               num_device_sms, launch_stream,
+                               launch_stream, phases);
-                               phases);
     };
     launcher(return_recv_hook ? LOW_LATENCY_SEND_PHASE : (LOW_LATENCY_SEND_PHASE | LOW_LATENCY_RECV_PHASE));
 
@@ -1237,9 +1219,8 @@ Buffer::low_latency_combine(const torch::Tensor& x, const torch::Tensor& topk_id
                               next_clean_meta.first, next_clean_meta.second,
                               num_combined_tokens, hidden, num_max_dispatch_tokens_per_rank,
                               num_topk, num_experts, rank, num_ranks,
-                              workspace, low_latency_usage_flag_mapped,
+                              workspace, num_device_sms,
-                              num_device_sms, launch_stream,
+                              launch_stream, phases, zero_copy);
-                              phases, zero_copy);
     };
     launcher(return_recv_hook ? LOW_LATENCY_SEND_PHASE : (LOW_LATENCY_SEND_PHASE | LOW_LATENCY_RECV_PHASE));
 
@@ -1328,7 +1309,6 @@ PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
         .def("intranode_combine", &deep_ep::Buffer::intranode_combine)
         .def("internode_dispatch", &deep_ep::Buffer::internode_dispatch)
         .def("internode_combine", &deep_ep::Buffer::internode_combine)
-        .def("get_low_latency_usage_flag", &deep_ep::Buffer::get_low_latency_usage_flag)
         .def("clean_low_latency_buffer", &deep_ep::Buffer::clean_low_latency_buffer)
         .def("low_latency_dispatch", &deep_ep::Buffer::low_latency_dispatch)
         .def("low_latency_combine", &deep_ep::Buffer::low_latency_combine)

csrc/deep_ep.hpp

@@ -71,10 +71,6 @@ private:
     volatile int* moe_recv_rdma_counter = nullptr;
     int* moe_recv_rdma_counter_mapped = nullptr;
 
-    // Host-side low-latency kernels' usages
-    volatile int* low_latency_usage_flag = nullptr;
-    int* low_latency_usage_flag_mapped = nullptr;
-
 public:
     Buffer(int rank, int num_ranks, int64_t num_nvl_bytes, int64_t num_rdma_bytes, bool low_latency_mode);
 
@@ -134,8 +130,6 @@ public:
                       const torch::Tensor& combined_rdma_head, const torch::Tensor& combined_nvl_head,
                       const Config& config, std::optional<EventHandle>& previous_event, bool async, bool allocate_on_comm_stream);
 
-    uint64_t get_low_latency_usage_flag() const;
-
     void clean_low_latency_buffer(int num_max_dispatch_tokens_per_rank, int hidden, int num_experts);
 
     std::tuple<torch::Tensor, std::optional<torch::Tensor>, torch::Tensor, torch::Tensor, torch::Tensor, std::optional<EventHandle>, std::optional<std::function<void()>>>

csrc/kernels/api.cuh

@@ -147,9 +147,8 @@ void dispatch(void* packed_recv_x, void* packed_recv_x_scales,
               int num_tokens, int hidden, int num_max_dispatch_tokens_per_rank,
               int num_topk, int num_experts, int rank, int num_ranks,
               bool use_fp8, bool round_scale, bool use_ue8m0,
-              void* workspace, int* usage_flag,
+              void* workspace, int num_device_sms,
-              int num_device_sms, cudaStream_t stream,
+              cudaStream_t stream, int phases);
-              int phases);
 
 void combine(void* combined_x,
              void* rdma_recv_x, int* rdma_recv_flag, void* rdma_send_x,
@@ -158,9 +157,8 @@ void combine(void* combined_x,
              int* next_clean, int num_next_clean_int,
              int num_combined_tokens, int hidden, int num_max_dispatch_tokens_per_rank,
              int num_topk, int num_experts, int rank, int num_ranks,
-             void* workspace, int* usage_flag,
+             void* workspace, int num_device_sms,
-             int num_device_sms, cudaStream_t stream,
+             cudaStream_t stream, int phases, bool zero_copy);
-             int phases, bool zero_copy);
 
 } // namespace internode_ll
 

csrc/kernels/internode_ll.cu

@@ -48,9 +48,8 @@ dispatch(void* packed_recv_x, void* packed_recv_x_scales,
          int* next_clean, int num_next_clean_int,
          int num_tokens, int num_max_dispatch_tokens_per_rank,
          int num_topk, int num_experts, int rank, int num_ranks,
-         bool round_scale, int* usage_flag,
          int num_warp_groups, int num_warps_per_group,
-         int phases) {
+         bool round_scale, int phases) {
     const auto sm_id = static_cast<int>(blockIdx.x);
     const auto thread_id = static_cast<int>(threadIdx.x);
     const auto warp_id = thread_id / 32, lane_id = get_lane_id();
@@ -189,10 +188,6 @@ dispatch(void* packed_recv_x, void* packed_recv_x_scales,
             #pragma unroll
             for (int i = lane_id; i < num_experts; i += 32)
                 atomic_add_release_global(atomic_finish_counter_per_expert + i, FINISHED_SUM_TAG);
-        } else if (sm_id == 1) {
-            // The second SM is also responsible for notifying PCIe usage
-            if (lane_id == 0)
-                atomicAdd_system(usage_flag, 1);
         }
 
         // This SM should be responsible for some destination experts, read `topk_idx` for them
@@ -341,9 +336,8 @@ void dispatch(void* packed_recv_x, void* packed_recv_x_scales,
               int num_tokens, int hidden, int num_max_dispatch_tokens_per_rank,
               int num_topk, int num_experts, int rank, int num_ranks,
               bool use_fp8, bool round_scale, bool use_ue8m0,
-              void* workspace, int* usage_flag,
+              void* workspace, int num_device_sms,
-              int num_device_sms, cudaStream_t stream,
+              cudaStream_t stream, int phases) {
-              int phases) {
     constexpr int kNumMaxTopK = 9;
     const int num_warp_groups = ceil_div(num_experts, num_device_sms);
     const int num_warps_per_group = 32 / num_warp_groups;
@@ -380,9 +374,8 @@ LAUNCH_KERNEL(&cfg, dispatch_func, \
               next_clean, num_next_clean_int, \
               num_tokens, num_max_dispatch_tokens_per_rank, \
               num_topk, num_experts, rank, num_ranks, \
-              round_scale, usage_flag, \
               num_warp_groups, num_warps_per_group, \
-              phases); } break
+              round_scale, phases); } break
 
     SETUP_LAUNCH_CONFIG(num_sms, num_warps * 32, stream);
     SWITCH_HIDDEN(DISPATCH_LAUNCH_CASE);
@@ -400,7 +393,6 @@ combine(void* combined_x,
         int num_combined_tokens, int hidden, int num_topk,
         int num_max_dispatch_tokens_per_rank,
         int num_experts, int rank, int num_ranks,
-        int* usage_flag,
         int num_warp_groups, int num_warps_per_group,
         int phases, bool zero_copy) {
     const auto sm_id = static_cast<int>(blockIdx.x);
@@ -497,13 +489,11 @@ combine(void* combined_x,
     if ((phases & LOW_LATENCY_RECV_PHASE) == 0)
         return;
 
-    // Wait all ranks to arrive and notify usages
+    // Wait all ranks to arrive
     if (responsible_expert_idx < num_experts) {
         EP_DEVICE_ASSERT(num_warps_per_group > 1);
         if (sub_warp_id == 0 and lane_id == 0) {
             while (ld_acquire_sys_global(rdma_recv_flag + responsible_expert_idx) == 0);
-        } else if (sm_id == 0 and sub_warp_id == 1 and lane_id == 0) {
-            atomicAdd_system(usage_flag, 1);
         }
     }
     cg::this_grid().sync();
@@ -555,9 +545,8 @@ void combine(void* combined_x,
              int* next_clean, int num_next_clean_int,
              int num_combined_tokens, int hidden, int num_max_dispatch_tokens_per_rank,
              int num_topk, int num_experts, int rank, int num_ranks,
-             void* workspace, int* usage_flag,
+             void* workspace, int num_device_sms,
-             int num_device_sms, cudaStream_t stream,
+             cudaStream_t stream, int phases, bool zero_copy) {
-             int phases, bool zero_copy) {
     constexpr int kNumMaxTopk = 9;
     const int num_warp_groups = ceil_div(num_experts, num_device_sms);
     const int num_warps_per_group = 32 / num_warp_groups;
@@ -582,7 +571,6 @@ LAUNCH_KERNEL(&cfg, combine_func, \
               num_combined_tokens, hidden, num_topk, \
               num_max_dispatch_tokens_per_rank, \
               num_experts, rank, num_ranks, \
-              usage_flag, \
               num_warp_groups, num_warps_per_group, \
               phases, zero_copy); } break
 

deep_ep/buffer.py

@@ -457,19 +457,6 @@ class Buffer:
             async_finish, allocate_on_comm_stream)
         return combined_x, combined_topk_weights, EventOverlap(event)
 
-    def get_low_latency_usage_flag(self):
-        """
-        Return a host-side integer flag, which indicates the stages of low-latency kernels.
-        The initial value is 0, the low-latency dispatch will add 1 before communication, the low-latency combine
-            will add 1 after communication.
-        This is useful when there is no two-batch overlap, and you want to overlap H2D/D2H transfer with attention layers.
-
-        Returns:
-            flag: the host-side integer flag pointer. The value is in `int`, but returns a `uint64_t` pointer. Please
-                `reinterpret_cast` the returned value into `int*`.
-        """
-        return self.runtime.get_low_latency_usage_flag()
-
     def clean_low_latency_buffer(self, num_max_dispatch_tokens_per_rank: int, hidden: int, num_experts: int) -> None:
         """
         As low-latency kernels require part of the buffer to be zero-initialized, so it is vital to clean the buffer

tests/test_low_latency.py

@@ -166,7 +166,6 @@ def test_loop(local_rank: int, num_local_ranks: int):
         print(f'Allocating buffer size: {num_rdma_bytes / 1e6} MB ...', flush=True)
     buffer = deep_ep.Buffer(group, num_rdma_bytes=num_rdma_bytes, low_latency_mode=True,
                             num_qps_per_rank=num_experts // num_ranks)
-    buffer.get_low_latency_usage_flag()
     test_main(num_tokens, hidden, num_experts, num_topk, rank, num_ranks, group, buffer, seed=1)
 
     do_pressure_test = False