[Unity] Disco: A Framework-Agnostic SPMD Runtime for Distributed Infe…

…rence/Training (#15622)

* [CMake] Add NCCL to TVM and TVM Runtime (#15605)

This PR introduces NCCL in the cmake system.
NCCL is NVIDIA's library for distributed communication.

* [Runtime] Expose ModuleGetFunction as PackedFunc (#15623)

This PR exposes `Module.GetFunction` as a global PackedFunc.
Previously, the only way to access this method is via TVM's
C API, but the C++ PackedFunc API is missing. This PR patches
this issue.

* [Runtime] Utils to Stringify Device (#15630)

There exist some basic functionality to convert Device and DLDeviceType
to std::string, but they are not following the common naming convention
in TVM, and thus less discoverable. This commit makes changes
accordingly:
- `runtime::DeviceName` to `runtime::DLDeviceType2Str`
- move declaration of `operator << (std::ostream&, Device)` from
  `runtime/device_api.h` to `runtime/packed_func.h`

* [RPC] Enhance RPC Protocol to support TVM Object (#15631)

This PR introduces object support in TVM RPC protocol by introducing three
new interfaces in `rpc_reference.h`:
- `uint64_t GetObjectBytes(Object* obj)`, which is a required
  implementation that returns the length of the object during serialization;
- `void WriteObject(Object* obj)` used to serialize an object to a
  writable channel;
- `void ReadObject(int* type_code, TVMValue* value)`, which deserializes
  a TVM Object from a channel.

To serialize an object, a recommended paradigm is to write its
`type_index` first, and then its content. For example, `ShapeTuple` can
be serialized as:

```C++
// pseudocode
void WriteObject(Object* obj) {
  if (obj is ShapeTuple) {
    this->Write<uint32_t>(type_index of ShapeTuple);
    this->Write<int32_t>(obj->ndim);
    this->WriteArray<int64_t>(obj->shape);
  } else {
    throw Unsupported;
  }
}

uint64_t GetObjectBytes(Object* obj) {
  uint64_t result = 0;
  if (obj is ShapeTuple) {
    result += sizeof(uint32_t); # for `type_index`
    result += sizeof(int32_t);  # for `ndim`
    result += sizeof(int64_t) * obj->ndim; # for content of the shape
  } else {
    throw Unsupported;
  }
  return result;
}
```

To deserialize an object, similar to serialization, the recommended
approach paradigm is to read `type_index` and disptch based on it.

Caveat on deserialization: RPC Reference itself does not own or allocate
any memory to store objects, meaning extra logic is usually required in
`ReadObject` to keep their liveness.

* [Unity] Disco: A Framework-Agnostic SPMD Runtime for Distributed Inference/Training

Disco is a distributed runtime that consists of a controler and a cluster of workers. The
controler is responsible for managing the workers by broadcasting commands to all the workers
together, and the workers are responsible for executing the commands and. The controler and
workers communicate with each other through a bi-directional channel.

Different from a generic system, Disco is designed to as "single-program-multiple-data" (SPMD)
runtime, which means that all the workers execute the same instruction at the same time, but the
data they are working on may be different. For example, in data parallelism, each worker may
work on a different batches of the data, but they all execute the same set of instructions.
Therefore, imagine there is a virtual machine that executes the program, the structures of
workers' register files could be considered as "identical" (single program) although the values
may differ (multiple data).

**DRef.** Following the design above, consider the program in SPMD in a virtual ISA, then each
worker is a virtual machine instance to execute the ISA maintaining its own register file.
The controler denotes each of their register files with a unique integer "register id",
and the workers use this id to refer to the register file that resides on itself.
DRef is a control-side object backed by such a register id. The data it contains is not assumed
to be directly accessible by the controler, with an exception for worker-0, which is a special
worker that is always co-located with the controler.

**Worker-0.** Worker-0 is a special worker that is always co-located with the controler.
It is assumed that the controler can synchronize with and access the registers of worker-0.
The Disco session provides multiple APIs to interact specifically with the worker-0.
To shared data with other workers, a common paradigm in Disco is to copy data from the
controler-side NDArray to the worker-0, and then copy it to other workers using primitives on
the data plane, for example, `broadcast` and `send`.

**Control plane.** The controler broadcasts commands to all the workers as control signals.
For example, the control may ask all workers to load a library or call a function respectively.
Common control signals include: shutdown, retrievel a global PackedFunc, call packed function,
etc. The controler is assumed to keep a message channel to each worker to implement the broadcast
behavior, and the message channel may vary depends on usecases.

**Data plane.** The data channel is usually used to exchange data between workers, especially for
tensor data which is usually large. For example, performing an allreduce operator for sharded
matrix multiplication, or broadcasting for an input tensor. For efficiency, the data channel is
usually backed by NCCL on NVIDIA GPUs, RCCL on AMD GPUs, or MPI on CPUs.

**Session.** A Disco session is a primary interface to interact with the Disco runtime, serving
as a global context that manages the control and workers. It could be implemented as a
multi-threaded with a pool of workers for single-node multi-gpu scenarios, or TCP sockets for
workloads that span over a cluster of nodes.

**Channel.** Disco channel is a bi-directional communication channel between the controler and
workers for exchanging control signals. It is no different from a generic RPC channel, but
adopts TVM's PackedFunc calling convention to support polymorphic and variadic arguments.

Co-Authored-by: Lesheng Jin <[email protected]>

---------

Co-authored-by: Lesheng Jin <[email protected]>

CMakeLists.txt

@@ -6,6 +6,7 @@ include(cmake/utils/Utils.cmake)
 include(cmake/utils/Summary.cmake)
 include(cmake/utils/Linker.cmake)
 include(cmake/utils/FindCUDA.cmake)
+include(cmake/utils/FindNCCL.cmake)
 include(cmake/utils/FindOpenCL.cmake)
 include(cmake/utils/FindVulkan.cmake)
 include(cmake/utils/FindLLVM.cmake)
@@ -25,6 +26,7 @@ endif()
 # and add set(OPTION VALUE) to override these build options.
 # Alernatively, use cmake -DOPTION=VALUE through command-line.
 tvm_option(USE_CUDA "Build with CUDA" OFF)
+tvm_option(USE_NCCL "Build with NCCL" OFF)
 tvm_option(USE_OPENCL "Build with OpenCL" OFF)
 tvm_option(USE_OPENCL_ENABLE_HOST_PTR "Enable OpenCL memory object access to host" OFF)
 tvm_option(USE_OPENCL_GTEST "Path to OpenCL specific gtest version for runtime cpp tests." /path/to/opencl/gtest)
@@ -350,6 +352,7 @@ list(APPEND COMPILER_SRCS "src/target/datatype/myfloat/myfloat.cc")
 tvm_file_glob(GLOB RUNTIME_SRCS
   src/runtime/*.cc
   src/runtime/vm/*.cc
+  src/runtime/disco/*.cc
   src/runtime/minrpc/*.cc
   src/runtime/relax_vm/*.cc
 )
@@ -434,6 +437,13 @@ if(USE_PROFILER)
   list(APPEND RUNTIME_SRCS ${RUNTIME_VM_PROFILER_SRCS})
 endif(USE_PROFILER)
 
+if(USE_CUDA AND USE_NCCL)
+  message(STATUS "Build with NCCL...")
+  find_nccl(${USE_NCCL})
+  tvm_file_glob(GLOB RUNTIME_NCCL_SRC src/runtime/disco/nccl/*.cc)
+  list(APPEND RUNTIME_SRCS ${RUNTIME_NCCL_SRC})
+endif()
+
 if(USE_AOT_EXECUTOR)
   message(STATUS "Build with AOT Executor support...")
   file(GLOB RUNTIME_AOT_EXECUTOR_SRCS src/runtime/aot_executor/*.cc)
@@ -850,3 +860,8 @@ if(USE_CUDA AND USE_CUTLASS)
   target_link_libraries(tvm PRIVATE -Wl,--no-as-needed flash_attn)
   target_link_libraries(tvm_runtime PRIVATE -Wl,--no-as-needed flash_attn)
 endif()
+
+if(USE_CUDA AND USE_NCCL)
+  target_link_libraries(tvm_runtime PRIVATE nccl)
+  target_link_libraries(tvm PRIVATE nccl)
+endif()

cmake/config.cmake

@@ -48,6 +48,12 @@
 # - /path/to/cuda: use specific path to cuda toolkit
 set(USE_CUDA OFF)
 
+# Whether to enable NCCL support:
+# - ON: enable NCCL with cmake's auto search
+# - OFF: disable NCCL
+# - /path/to/nccl: use specific path to nccl
+set(USE_NCCL OFF)
+
 # Whether enable ROCM runtime
 #
 # Possible values:

cmake/modules/LibInfo.cmake

@@ -64,6 +64,7 @@ function(add_lib_info src_file)
     TVM_INFO_USE_CPP_RTVM="${USE_CPP_RTVM}"
     TVM_INFO_USE_CUBLAS="${USE_CUBLAS}"
     TVM_INFO_USE_CUDA="${USE_CUDA}"
+    TVM_INFO_USE_NCCL="${USE_NCCL}"
     TVM_INFO_USE_CUDNN="${USE_CUDNN}"
     TVM_INFO_USE_CUSTOM_LOGGING="${USE_CUSTOM_LOGGING}"
     TVM_INFO_USE_CUTLASS="${USE_CUTLASS}"

cmake/utils/FindNCCL.cmake

@@ -0,0 +1,56 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+# Variables used by this module, they can change the default behaviour and need
+# to be set before calling find_package:
+#
+#  NCCL_ROOT - When set, this path is inspected instead of standard library
+#              locations as the root of the NCCL installation.
+#              The environment variable NCCL_ROOT overrides this variable.
+#
+# This module defines
+#  Nccl_FOUND, whether nccl has been found
+#  NCCL_INCLUDE_DIR, directory containing header
+#  NCCL_LIBRARY, directory containing nccl library
+# This module assumes that the user has already called find_package(CUDA)
+
+macro(find_nccl use_nccl)
+  if(${use_nccl} MATCHES ${IS_FALSE_PATTERN})
+    return()
+  endif()
+  if(${use_nccl} MATCHES ${IS_TRUE_PATTERN})
+    find_path(NCCL_INCLUDE_DIR NAMES nccl.h)
+    find_library(NCCL_LIBRARY NAMES nccl)
+  else()
+    find_path(NCCL_INCLUDE_DIR NAMES nccl.h HINTS ${use_nccl} ${use_nccl}/include)
+    find_library(NCCL_LIBRARY NAMES nccl HINTS ${use_nccl} ${use_nccl}/lib)
+  endif()
+  include(FindPackageHandleStandardArgs)
+  find_package_handle_standard_args(Nccl DEFAULT_MSG NCCL_INCLUDE_DIR NCCL_LIBRARY)
+  if (Nccl_FOUND)
+    message(STATUS "Found NCCL_LIBRARY: ${NCCL_LIBRARY}")
+    message(STATUS "Found NCCL_INCLUDE_DIR: ${NCCL_INCLUDE_DIR}")
+    add_library(nccl SHARED IMPORTED)
+    set_target_properties(nccl
+      PROPERTIES
+      INTERFACE_INCLUDE_DIRECTORIES "${NCCL_INCLUDE_DIR}"
+      IMPORTED_LOCATION             "${NCCL_LIBRARY}")
+  else()
+    message(STATUS "NCCL not found")
+  endif()
+  mark_as_advanced(NCCL_INCLUDE_DIR NCCL_LIBRARY)
+endmacro(find_nccl)

include/tvm/relax/attrs/ccl.h

@@ -0,0 +1,46 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+/*!
+ * \file tvm/relax/attrs/ccl.h
+ * \brief Attributes for ccl operators.
+ */
+#ifndef TVM_RELAX_ATTRS_CCL_H_
+#define TVM_RELAX_ATTRS_CCL_H_
+
+#include <tvm/relax/expr.h>
+
+namespace tvm {
+namespace relax {
+
+/*! \brief Attributes used in allreduce operators */
+struct AllReduceAttrs : public tvm::AttrsNode<AllReduceAttrs> {
+  String op_type;
+
+  TVM_DECLARE_ATTRS(AllReduceAttrs, "relax.attrs.AllReduceAttrs") {
+    TVM_ATTR_FIELD(op_type).describe(
+        "The type of reduction operation to be applied to the input data. Now only sum is "
+        "supported.");
+  }
+};  // struct AllReduceAttrs
+
+}  // namespace relax
+}  // namespace tvm
+
+#endif  // TVM_RELAX_ATTRS_CCL_H_

include/tvm/runtime/data_type.h

@@ -339,6 +339,7 @@ inline const char* DLDataTypeCode2Str(DLDataTypeCode type_code) {
     default:
       LOG(FATAL) << "unknown type_code=" << static_cast<int>(type_code);
   }
+  throw;
 }
 
 inline std::ostream& operator<<(std::ostream& os, DLDataType t) {  // NOLINT(*)

include/tvm/runtime/device_api.h

@@ -245,54 +245,6 @@ class TVM_DLL DeviceAPI {
 constexpr int kRPCSessMask = 128;
 static_assert(kRPCSessMask >= TVMDeviceExtType_End);
 
-/*!
- * \brief The name of Device API factory.
- * \param type The device type.
- * \return the device name.
- */
-inline const char* DeviceName(int type) {
-  switch (type) {
-    case kDLCPU:
-      return "cpu";
-    case kDLCUDA:
-      return "cuda";
-    case kDLCUDAHost:
-      return "cuda_host";
-    case kDLCUDAManaged:
-      return "cuda_managed";
-    case kDLOpenCL:
-      return "opencl";
-    case kDLSDAccel:
-      return "sdaccel";
-    case kDLAOCL:
-      return "aocl";
-    case kDLVulkan:
-      return "vulkan";
-    case kDLMetal:
-      return "metal";
-    case kDLVPI:
-      return "vpi";
-    case kDLROCM:
-      return "rocm";
-    case kDLROCMHost:
-      return "rocm_host";
-    case kDLExtDev:
-      return "ext_dev";
-    case kDLOneAPI:
-      return "oneapi";
-    case kDLWebGPU:
-      return "webgpu";
-    case kDLHexagon:
-      return "hexagon";
-    case kOpenGL:
-      return "opengl";
-    case kDLMicroDev:
-      return "microdev";
-    default:
-      LOG(FATAL) << "unknown type =" << type;
-  }
-}
-
 /*!
  * \brief Return true if a Device is owned by an RPC session.
  */
@@ -324,7 +276,7 @@ inline std::ostream& operator<<(std::ostream& os, DLDevice dev) {  // NOLINT(*)
     os << "remote[" << tvm::runtime::GetRPCSessionIndex(dev) << "]-";
     dev = tvm::runtime::RemoveRPCSessionMask(dev);
   }
-  os << tvm::runtime::DeviceName(static_cast<int>(dev.device_type)) << "(" << dev.device_id << ")";
+  os << tvm::runtime::DLDeviceType2Str(static_cast<int>(dev.device_type)) << ":" << dev.device_id;
   return os;
 }