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[None][feat] Add TRTLLM_NIXL_KVCACHE_BACKEND environment variable for NIXL backend selection #9075

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Merged
merged 1 commit into from
Nov 17, 2025
Merged

[None][feat] Add TRTLLM_NIXL_KVCACHE_BACKEND environment variable for NIXL backend selection #9075

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22 changes: 22 additions & 0 deletions cpp/tensorrt_llm/common/envUtils.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -318,6 +318,28 @@ std::string getEnvNixlInterface()
return nixlInterface;
}

std::string getEnvNixlBackend()
{
static std::once_flag flag;
static std::string nixlBackend;

std::call_once(flag,
[&]()
{
char const* nixl_backend = std::getenv("TRTLLM_NIXL_KVCACHE_BACKEND");
if (nixl_backend)
{
nixlBackend = nixl_backend;
}
else
{
// Default to UCX if not specified
nixlBackend = "UCX";
}
});
return nixlBackend;
}

bool getEnvDisaggLayerwise()
{
static bool const disaggLayerwise = getBoolEnv("TRTLLM_DISAGG_LAYERWISE");
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2 changes: 2 additions & 0 deletions cpp/tensorrt_llm/common/envUtils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,8 @@ std::string getEnvUCXInterface();

std::string getEnvNixlInterface();

std::string getEnvNixlBackend();

bool getEnvDisaggLayerwise();

bool getEnvParallelCacheSend();
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19 changes: 16 additions & 3 deletions cpp/tensorrt_llm/executor/cache_transmission/nixl_utils/transferAgent.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@
#include <netdb.h>
#include <netinet/in.h>
#include <nixl_types.h>
#include <set>
#include <sys/file.h>
#include <sys/stat.h>
#include <unistd.h>
Expand Down Expand Up @@ -345,15 +346,27 @@ NixlTransferAgent::NixlTransferAgent(BaseAgentConfig const& config)
mRawAgent = std::make_unique<nixlAgent>(config.mName, std::move(nixlConfig));
}

std::string nixlBackend = common::getEnvNixlBackend();
// List of supported backends - extend this list as new backends are added
static const std::set<std::string> kSUPPORTED_BACKENDS = {"UCX"};

if (kSUPPORTED_BACKENDS.find(nixlBackend) == kSUPPORTED_BACKENDS.end())
{
TLLM_LOG_ERROR("Unsupported NIXL backend: %s, fallback to UCX", nixlBackend.c_str());
nixlBackend = "UCX";
}

TLLM_LOG_INFO("NixlTransferAgent::NixlTransferAgent using NIXL backend: %s", nixlBackend.c_str());

nixl_b_params_t init1;
nixl_mem_list_t mems1;
status = mRawAgent->getPluginParams("UCX", mems1, init1);
status = mRawAgent->getPluginParams(nixlBackend.c_str(), mems1, init1);
TLLM_CHECK(status == NIXL_SUCCESS);

status = mRawAgent->createBackend("UCX", init1, mRawBackend);
status = mRawAgent->createBackend(nixlBackend.c_str(), init1, mRawBackend);
if (status != NIXL_SUCCESS || !mRawBackend)
{
TLLM_THROW("Failed to create NIXL backend");
TLLM_THROW("Failed to create NIXL backend: %s", nixlBackend.c_str());
}
mExtraParams.backends.push_back(mRawBackend);
TLLM_LOG_INFO("NixlTransferAgent::NixlTransferAgent mAddress: %s", mAddress.c_str());
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