2.18.1-1

Add support for IB SHARP to NVLS (NVLink SHARP algorithm).
Add NVLS+Tree algorithm.
Add support for memory management using cuMem* functions.
Use all NICs for Send/Receive operations on systems with more than
one NIC per GPU (#804).
Add ncclCommSplit primitive, with resource sharing option in config.
Fix alltoallv hang (#788)
Increase number of channels on H100 when we're not limited by NVLink.
Improve error reporting in case of IB failure, printing local and
remote ID (#779).
Add build option to allow compilation against RDMA includes instead
of dynamically loading IB verbs symbols (#802).
Fix context creation for progress thread (#803).
NET/IB: add option to use multiple QPs in round-robin mode.
Fix tree performance issue when NVB is disabled on HCM topologies.

src/misc/cudawrap.cc

@@ -6,10 +6,46 @@
 
 #include "nccl.h"
 #include "debug.h"
+#include "param.h"
 #include "cudawrap.h"
 
 #include <dlfcn.h>
 
+// This env var (NCCL_CUMEM_ENABLE) toggles cuMem API usage
+NCCL_PARAM(CuMemEnable, "CUMEM_ENABLE", 0);
+
+static int ncclCuMemSupported = 0;
+
+// Determine whether CUMEM & VMM RDMA is supported on this platform
+int ncclIsCuMemSupported() {
+#if CUDART_VERSION < 11030
+  return 0;
+#else
+  CUdevice currentDev;
+  int cudaDev;
+  int cudaDriverVersion;
+  int flag = 0;
+  ncclResult_t ret = ncclSuccess;
+  CUDACHECKGOTO(cudaDriverGetVersion(&cudaDriverVersion), ret, error);
+  if (cudaDriverVersion < 12000) return 0;  // Need CUDA_VISIBLE_DEVICES support
+  CUDACHECKGOTO(cudaGetDevice(&cudaDev), ret, error);
+  if (CUPFN(cuMemCreate) == NULL) return 0;
+  CUCHECKGOTO(cuDeviceGet(&currentDev, cudaDev), ret, error);
+  // Query device to see if CUMEM VMM support is available
+  CUCHECKGOTO(cuDeviceGetAttribute(&flag, CU_DEVICE_ATTRIBUTE_VIRTUAL_MEMORY_MANAGEMENT_SUPPORTED, currentDev), ret, error);
+  if (!flag) return 0;
+  // Query device to see if CUMEM RDMA support is available
+  CUCHECKGOTO(cuDeviceGetAttribute(&flag, CU_DEVICE_ATTRIBUTE_GPU_DIRECT_RDMA_WITH_CUDA_VMM_SUPPORTED, currentDev), ret, error);
+  if (!flag) return 0;
+error:
+  return (ret == ncclSuccess);
+#endif
+}
+
+int ncclCuMemEnable() {
+  return ((ncclParamCuMemEnable() == -2 && ncclCuMemSupported) || ncclParamCuMemEnable());
+}
+
 #define DECLARE_CUDA_PFN(symbol,version) PFN_##symbol##_v##version pfn_##symbol = nullptr
 
 #if CUDART_VERSION >= 11030
@@ -35,6 +71,7 @@ DECLARE_CUDA_PFN(cuMemExportToShareableHandle, 10020);
 DECLARE_CUDA_PFN(cuMemImportFromShareableHandle, 10020);
 DECLARE_CUDA_PFN(cuMemMap, 10020);
 DECLARE_CUDA_PFN(cuMemRelease, 10020);
+DECLARE_CUDA_PFN(cuMemRetainAllocationHandle, 11000);
 DECLARE_CUDA_PFN(cuMemSetAccess, 10020);
 DECLARE_CUDA_PFN(cuMemUnmap, 10020);
 #if CUDA_VERSION >= 11070
@@ -89,7 +126,6 @@ static ncclResult_t cudaPfnFuncLoader(void) {
   LOAD_SYM(cuCtxSetCurrent, 4000, 1);
   LOAD_SYM(cuCtxGetDevice, 2000, 1);
 /* cuMem API support */
-#if CUDA_VERSION >= 11030
   LOAD_SYM(cuMemAddressReserve, 10020, 1);
   LOAD_SYM(cuMemAddressFree, 10020, 1);
   LOAD_SYM(cuMemCreate, 10020, 1);
@@ -98,9 +134,9 @@ static ncclResult_t cudaPfnFuncLoader(void) {
   LOAD_SYM(cuMemImportFromShareableHandle, 10020, 1);
   LOAD_SYM(cuMemMap, 10020, 1);
   LOAD_SYM(cuMemRelease, 10020, 1);
+  LOAD_SYM(cuMemRetainAllocationHandle, 11000, 1);
   LOAD_SYM(cuMemSetAccess, 10020, 1);
   LOAD_SYM(cuMemUnmap, 10020, 1);
-#endif
 #if CUDA_VERSION >= 11070
   LOAD_SYM(cuMemGetHandleForAddressRange, 11070, 1); // DMA-BUF support
 #endif
@@ -135,7 +171,7 @@ static void initOnceFunc() {
   if (ncclCudaPath == NULL)
     snprintf(path, 1024, "%s", "libcuda.so");
   else
-    snprintf(path, 1024, "%s%s", ncclCudaPath, "libcuda.so");
+    snprintf(path, 1024, "%s/%s", ncclCudaPath, "libcuda.so");
 
   (void) dlerror(); // Clear any previous errors
   cudaLib = dlopen(path, RTLD_LAZY);
@@ -195,6 +231,9 @@ static void initOnceFunc() {
   }
   #endif
 
+  // Determine whether we support the cuMem APIs or not
+  ncclCuMemSupported = ncclIsCuMemSupported();
+
   initResult = ncclSuccess;
   return;
 error: