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Reduce memory footprint for allreduce8 and allgather6 #644

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Merged
Binyang2014 merged 2 commits into from
Oct 3, 2025
Merged

Reduce memory footprint for allreduce8 and allgather6 #644

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b73552f
Reduce memory footprint
Binyang2014 Oct 3, 2025
1274510
update
Binyang2014 Oct 3, 2025
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7 changes: 3 additions & 4 deletions apps/nccl/src/allgather.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ AllgatherAlgo6::AllgatherAlgo6() : disableChannelCache_(false) {
void AllgatherAlgo6::initialize(std::shared_ptr<mscclpp::Communicator> comm,
std::unordered_map<std::string, std::shared_ptr<void>>&) {
this->conns_ = setupConnections(comm);
this->memorySemaphores_ = std::move(setupMemorySemaphores(comm, this->conns_, nChannelsPerConnection_));
}

ncclResult_t AllgatherAlgo6::allgatherKernelFunc(const std::shared_ptr<mscclpp::AlgorithmCtx> ctx, const void* input,
Expand Down Expand Up @@ -61,15 +62,13 @@ ncclResult_t AllgatherAlgo6::allgatherKernelFunc(const std::shared_ptr<mscclpp::
std::shared_ptr<mscclpp::AlgorithmCtx> AllgatherAlgo6::initAllgatherContext(std::shared_ptr<mscclpp::Communicator> comm,
const void*, void* output, size_t count,
ncclDataType_t dtype) {
constexpr int nChannelsPerConnection = 35;

auto ctx = std::make_shared<mscclpp::AlgorithmCtx>();
ctx->rank = comm->bootstrap()->getRank();
ctx->workSize = comm->bootstrap()->getNranks();
ctx->nRanksPerNode = comm->bootstrap()->getNranksPerNode();

// setup semaphores
ctx->memorySemaphores = std::move(setupMemorySemaphores(comm, this->conns_, nChannelsPerConnection));
ctx->memorySemaphores = this->memorySemaphores_;

size_t bytes = count * ncclTypeSize(dtype);
size_t recvBytes;
Expand All @@ -88,7 +87,7 @@ std::shared_ptr<mscclpp::AlgorithmCtx> AllgatherAlgo6::initAllgatherContext(std:
comm->registerMemory((void*)recvBasePtr, recvBytes, mscclpp::Transport::CudaIpc);
std::vector<mscclpp::RegisteredMemory> remoteMemories = setupRemoteMemories(comm, ctx->rank, localMemory);
ctx->memoryChannels = std::move(
setupMemoryChannels(this->conns_, ctx->memorySemaphores, remoteMemories, localMemory, nChannelsPerConnection));
setupMemoryChannels(this->conns_, ctx->memorySemaphores, remoteMemories, localMemory, nChannelsPerConnection_));
ctx->memoryChannelDeviceHandles = setupMemoryChannelDeviceHandles(ctx->memoryChannels);

// keep registered memories reference
Expand Down
2 changes: 2 additions & 0 deletions apps/nccl/src/allgather.hpp
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Expand Up @@ -217,6 +217,8 @@ class AllgatherAlgo6 : public mscclpp::AlgorithmBuilder {
private:
bool disableChannelCache_;
std::vector<std::shared_ptr<mscclpp::Connection>> conns_;
std::vector<std::shared_ptr<mscclpp::MemoryDevice2DeviceSemaphore>> memorySemaphores_;
const int nChannelsPerConnection_ = 35;

void initialize(std::shared_ptr<mscclpp::Communicator> comm, std::unordered_map<std::string, std::shared_ptr<void>>&);
ncclResult_t allgatherKernelFunc(const std::shared_ptr<mscclpp::AlgorithmCtx> ctx, const void* input, void* output,
Expand Down
10 changes: 6 additions & 4 deletions apps/nccl/src/allreduce.cu
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Expand Up @@ -460,7 +460,8 @@ void Allreduce8::initialize(std::shared_ptr<mscclpp::Communicator> comm,
nChannelsPerConnection_ = 64;
comm_ = comm;
// setup semaphores
this->deviceSemaphores_ = setupMemorySemaphores(comm, this->conns_, nChannelsPerConnection_);
this->outputSemaphores_ = setupMemorySemaphores(comm, this->conns_, nChannelsPerConnection_);
this->inputScratchSemaphores_ = setupMemorySemaphores(comm, this->conns_, nChannelsPerConnection_);
mscclpp::RegisteredMemory localMemory =
comm->registerMemory(scratchBuffer_.get(), scratchBufferSize_, mscclpp::Transport::CudaIpc);
this->remoteScratchMemories_ = setupRemoteMemories(comm, comm->bootstrap()->getRank(), localMemory);
Expand All @@ -483,8 +484,9 @@ ncclResult_t Allreduce8::allreduceKernelFunc(const std::shared_ptr<mscclpp::Algo
} else {
mscclpp::RegisteredMemory localMemory =
comm_->registerMemory(const_cast<void*>(input), bytes, mscclpp::Transport::CudaIpc);
std::vector<mscclpp::MemoryChannel> channels = setupMemoryChannels(
this->conns_, this->deviceSemaphores_, this->remoteScratchMemories_, localMemory, nChannelsPerConnection_);
std::vector<mscclpp::MemoryChannel> channels =
setupMemoryChannels(this->conns_, this->inputScratchSemaphores_, this->remoteScratchMemories_, localMemory,
nChannelsPerConnection_);
this->memoryChannelsMap_[input] = std::make_pair(channels, setupMemoryChannelDeviceHandles(channels));
}
inputChannelHandles = this->memoryChannelsMap_[input].second;
Expand Down Expand Up @@ -525,7 +527,7 @@ std::shared_ptr<mscclpp::AlgorithmCtx> Allreduce8::initAllreduceContext(std::sha
ctx->nRanksPerNode = comm->bootstrap()->getNranksPerNode();

// setup semaphores
ctx->memorySemaphores = setupMemorySemaphores(comm, this->conns_, nChannelsPerConnection_);
ctx->memorySemaphores = this->outputSemaphores_;
// setup memories and channels
size_t recvBytes;
CUdeviceptr recvBasePtr;
Expand Down
3 changes: 2 additions & 1 deletion apps/nccl/src/allreduce.hpp
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Expand Up @@ -887,7 +887,8 @@ class Allreduce8 : public mscclpp::AlgorithmBuilder {
int nChannelsPerConnection_;
std::vector<std::shared_ptr<mscclpp::Connection>> conns_;
std::shared_ptr<char> scratchBuffer_;
std::vector<std::shared_ptr<mscclpp::MemoryDevice2DeviceSemaphore>> deviceSemaphores_;
std::vector<std::shared_ptr<mscclpp::MemoryDevice2DeviceSemaphore>> outputSemaphores_;
std::vector<std::shared_ptr<mscclpp::MemoryDevice2DeviceSemaphore>> inputScratchSemaphores_;
std::vector<mscclpp::RegisteredMemory> remoteScratchMemories_;
mscclpp::RegisteredMemory localScratchMemory_;
std::unordered_map<const void*, std::pair<std::vector<mscclpp::MemoryChannel>,
Expand Down
5 changes: 1 addition & 4 deletions apps/nccl/src/nccl.cu
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Expand Up @@ -875,10 +875,7 @@ NCCL_API ncclResult_t ncclAllToAllv(const void* sendbuff, [[maybe_unused]] const
}

NCCL_API ncclResult_t ncclGroupStart() {
if (!tryLoadNcclSharedLib()) {
WARN("Failed to load the shared library for nccl/rccl");
return ncclInternalError;
}
tryLoadNcclSharedLib();
if (mscclppNcclDlopenSharedLib == true) {
return mscclppNcclOps.GroupStart();
}
Expand Down
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