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Partial fix CUDA_LAUNCH_BLOCKING=1 #774

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Partial fix CUDA_LAUNCH_BLOCKING=1 #774

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19 changes: 17 additions & 2 deletions src/enqueue.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,19 @@
#include <cstring> // std::memcpy
#include <cinttypes> // PRIx64

static pthread_once_t initOnceControl = PTHREAD_ONCE_INIT;
static bool isCudaLaunchBlocking = false;

static void initOnceFunc() {
char* val = getenv("CUDA_LAUNCH_BLOCKING");
isCudaLaunchBlocking = val!=nullptr && val[0]!=0 && !(val[0]=='0' && val[1]==0);
}

static void initOnce() {
pthread_once(&initOnceControl, initOnceFunc);
}


static void* const ncclKernelGeneric = (void*)NCCL_KERN_NAME(SendRecv, RING, SIMPLE, Sum, int8_t);

struct ncclKernelMatch {
Expand Down Expand Up @@ -964,7 +977,8 @@ ncclResult_t ncclLaunchPrepare(struct ncclComm* comm) {
}
NCCLCHECKGOTO(ncclStrongStreamWaitStream(tasks->capturingGraph, launchStream, &comm->deviceStream), result, failure);

if (persistent || comm->persistentRefs != 0) {
initOnce(); // isCudaLaunchBlocking
if (persistent || comm->persistentRefs != 0 || isCudaLaunchBlocking) {
// We have to launch host tasks to push proxy args. We are careful to only
// do this if necessary since host tasks impose a high performance cost in CUDA.
bool acquired = false;
Expand Down Expand Up @@ -1087,7 +1101,8 @@ ncclResult_t ncclLaunchKernel(struct ncclComm* comm, struct ncclKernelPlan* plan
}

ncclResult_t ncclLaunchKernelAfter_NoCuda(struct ncclComm* comm, struct ncclKernelPlan* plan) {
if (comm->persistentRefs == 0) { // implies !plan->persistent
initOnce(); // isCudaLaunchBlocking
if (!(plan->persistent || comm->persistentRefs != 0 || isCudaLaunchBlocking)) {
// If this isn't being captured and there aren't any CUDA graphs alive
// then we don't need to do our proxyOp pushing on the host stream.
NCCLCHECK(hostStreamPlanTask(comm, plan));
Expand Down