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PR #40967: [xla:gpu] Cache NCCL Communicator properties #41071

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PR #40967: [xla:gpu] Cache NCCL Communicator properties #41071

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34 changes: 22 additions & 12 deletions xla/backends/gpu/collectives/nccl_communicator.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -240,9 +240,23 @@ class NcclCommunicator::NcclRegisteredBufferHandle
};

//==-----------------------------------------------------------------------===//
// NCCL Device Communicator
// NCCL Communicator
//==-----------------------------------------------------------------------===//

NcclCommunicator::NcclCommunicator(se::StreamExecutor* stream_executor,
ncclComm_t comm,
std::unique_ptr<tsl::Executor> executor,
std::shared_ptr<CancellationToken> cancel)
: stream_executor_(stream_executor),
comm_(comm),
executor_(std::move(executor)),
cancel_(std::move(cancel)),
supports_one_sided_comm_(QuerySupportsOneSidedComm()) {
VLOG(1) << absl::StreamFormat("[%d] Created NCCL communicator %s",
stream_executor_->device_ordinal(),
this->ToString());
}

bool NcclCommunicator::SupportsDeviceComm() const {
#if NCCL_VERSION_CODE >= 22800
return true;
Expand All @@ -252,6 +266,10 @@ bool NcclCommunicator::SupportsDeviceComm() const {
}

bool NcclCommunicator::SupportsOneSidedComm() const {
return supports_one_sided_comm_;
}

bool NcclCommunicator::QuerySupportsOneSidedComm() const {
#if NCCL_VERSION_CODE >= 22907
ncclCommProperties_t props = NCCL_COMM_PROPERTIES_INITIALIZER;
if (ncclCommQueryProperties(comm_, &props) == ncclSuccess) {
Expand All @@ -277,19 +295,11 @@ NcclCommunicator::CreateDeviceComm(
#endif // NCCL_VERSION_CODE >= 22800
}

//==-----------------------------------------------------------------------===//
// NCCL Symmetric Memory
//==-----------------------------------------------------------------------===//

absl::StatusOr<std::unique_ptr<SymmetricMemory>>
NcclCommunicator::CreateSymmetricMemory(se::DeviceAddressBase addr) {
return NcclSymmetricMemory::Create(comm_, addr);
}

//==-----------------------------------------------------------------------===//
// NCCL Communicator
//==-----------------------------------------------------------------------===//

absl::StatusOr<std::unique_ptr<NcclCommunicator>> NcclCommunicator::Create(
se::StreamExecutor* stream_executor,
absl::AnyInvocable<absl::StatusOr<ncclComm_t>()> make_comm,
Expand Down Expand Up @@ -757,7 +767,7 @@ absl::Status NcclCommunicator::LaunchAllGather(

// If all buffers are contiguous returns a device address range that covers
// all of them, otherwise returns an empty optional.
static std::optional<se::DeviceAddressBase> IsContinguous(
static std::optional<se::DeviceAddressBase> IsContiguous(
absl::Span<const se::DeviceAddressBase> buffers) {
if (buffers.empty()) {
return std::nullopt;
Expand Down Expand Up @@ -794,8 +804,8 @@ absl::Status NcclCommunicator::LaunchAllToAll(
absl::StrAppendFormat(out, "%p", buffer.opaque());
};

auto send_contiguous = IsContinguous(send_buffers);
auto recv_contiguous = IsContinguous(recv_buffers);
auto send_contiguous = IsContiguous(send_buffers);
auto recv_contiguous = IsContiguous(recv_buffers);

VLOG(3) << absl::StreamFormat(
"[%d] Launch NCCL AllToAll operation; send_buffers=[%s]; "
Expand Down
16 changes: 7 additions & 9 deletions xla/backends/gpu/collectives/nccl_communicator.h
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Original file line number Diff line number Diff line change
Expand Up @@ -172,15 +172,7 @@ class NcclCommunicator : public GpuCommunicator {

NcclCommunicator(se::StreamExecutor* stream_executor, ncclComm_t comm,
std::unique_ptr<tsl::Executor> executor,
std::shared_ptr<CancellationToken> cancel)
: stream_executor_(stream_executor),
comm_(comm),
executor_(std::move(executor)),
cancel_(std::move(cancel)) {
VLOG(1) << absl::StreamFormat("[%d] Created NCCL communicator %s",
stream_executor_->device_ordinal(),
this->ToString());
}
std::shared_ptr<CancellationToken> cancel);

absl::Status GroupStart();
absl::Status GroupEnd();
Expand Down Expand Up @@ -239,6 +231,9 @@ class NcclCommunicator : public GpuCommunicator {
const SignalDesc& signal_desc,
const Executor& executor) final;

// Queries NCCL for one-sided comm support. Called once at construction.
bool QuerySupportsOneSidedComm() const;

// Polls the communicator until any pending non-blocking operations are "done"
// or aborted.
absl::Status PollUntilDone() const;
Expand Down Expand Up @@ -291,6 +286,9 @@ class NcclCommunicator : public GpuCommunicator {
// Has comm_ been aborted?
bool aborted_ = false;

// Cached result of querying NCCL for one-sided comm support.
bool supports_one_sided_comm_ = false;

// Nesting level of current NCCL group
int group_nesting_level_ = 0;

Expand Down
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