1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
|
#include <torch/csrc/distributed/c10d/intra_node_comm.hpp>
#include <torch/csrc/distributed/c10d/DMAConnectivity.hpp>
#include <torch/csrc/distributed/c10d/Utils.hpp>
// #include <cuda_runtime.h>
namespace c10d::intra_node_comm {
// NOLINTNEXTLINE(misc-use-internal-linkage)
bool isIntraNodeCommSupported();
static std::vector<std::string> ENABLE_INTRA_NODE_COMM = {
"ENABLE_INTRA_NODE_COMM"};
// Forces detectedTopology() to return Topology::FULLY_CONNECTED, so
// IntraNodeComm can be used even without NVLink connection. This is only used
// for testing purposes.
static std::vector<std::string> TEST_INTRA_NODE_COMM = {"TEST_INTRA_NODE_COMM"};
static int intraNodeCommIdx = 0;
/**
* Query the nvlink connection among devices.
*/
static NvlMesh getNvlMesh(const std::vector<int>& rankToDeviceIdx) {
auto connectivity = detect_dma_connectivity(c10::DeviceType::CUDA, "nvlink");
NvlMesh nvlMesh = {};
for (size_t srcRank = 0; srcRank < kMaxDevices; ++srcRank) {
for (size_t dstRank = 0; dstRank < kMaxDevices; ++dstRank) {
if (srcRank < rankToDeviceIdx.size() &&
dstRank < rankToDeviceIdx.size()) {
nvlMesh[srcRank][dstRank] =
connectivity
->matrix[rankToDeviceIdx[srcRank]][rankToDeviceIdx[dstRank]];
}
}
}
return nvlMesh;
}
/**
* Detech topology given a NvlMesh.
*/
static Topology detectTopology(const NvlMesh nvlMesh, size_t worldSize) {
if (getCvarBool(TEST_INTRA_NODE_COMM, false)) {
return Topology::FULLY_CONNECTED;
}
bool fullyConnected = true;
for (size_t i = 0; i < worldSize - 1; ++i) {
for (size_t j = i + 1; j < worldSize; ++j) {
if (nvlMesh[i][j] == 0 || nvlMesh[j][i] == 0) {
fullyConnected = false;
}
}
}
if (fullyConnected) {
LOG(INFO) << "IntraNodeComm: Topology::FULLY_CONNECTED";
return Topology::FULLY_CONNECTED;
}
LOG(INFO) << "IntraNodeComm: Topology::UNKNOWN";
return Topology::UNKNOWN;
};
IntraNodeComm::IntraNodeComm(
c10::intrusive_ptr<c10d::Store> store,
size_t rank,
size_t worldSize,
std::optional<size_t> bufferSize)
: store_(std::move(store)),
rank_(rank),
worldSize_(worldSize),
bufferSize_(bufferSize.has_value() ? *bufferSize : kDefaultBufferSize) {}
IntraNodeComm::~IntraNodeComm() {
if (!isInitialized_) {
return;
}
auto allocator = get_allocator(c10::DeviceType::CUDA);
allocator->free(symmetricMemoryPtr_);
}
bool IntraNodeComm::isEnabled() {
return getCvarBool(ENABLE_INTRA_NODE_COMM, false);
}
/**
* Use c10d::Store to perform allgather on a trivially copyable type.
*/
template <typename T>
static std::vector<T> storeAllGather(
const c10::intrusive_ptr<c10d::Store>& store,
const std::string& prefix,
size_t rank,
size_t worldSize,
T val) {
static_assert(std::is_trivially_copyable_v<T>);
std::vector<std::string> peerKeys;
for (size_t r = 0; r < worldSize; ++r) {
std::ostringstream oss;
oss << prefix << "-" << r;
peerKeys.push_back(oss.str());
}
{
std::vector<uint8_t> payload(
reinterpret_cast<uint8_t*>(&val),
reinterpret_cast<uint8_t*>(&val) + sizeof(T));
store->set(peerKeys[rank], payload);
}
std::vector<T> peerVals;
for (size_t r = 0; r < worldSize; ++r) {
if (r == rank) {
peerVals.push_back(val);
continue;
}
store->wait({peerKeys[r]});
auto payload = store->get(peerKeys[r]);
TORCH_CHECK(payload.size() == sizeof(T));
T peerVal{};
std::memcpy(&peerVal, payload.data(), sizeof(T));
peerVals.push_back(peerVal);
}
return peerVals;
}
bool IntraNodeComm::rendezvous() {
if (isInitialized_) {
return true;
}
#if !defined(USE_ROCM) && defined(PYTORCH_C10_DRIVER_API_SUPPORTED)
if (!isIntraNodeCommSupported() || worldSize_ < 2 ||
worldSize_ > kMaxDevices) {
return false;
}
// NOLINTNEXTLINE(bugprone-signed-char-misuse)
deviceIdx_ = at::cuda::current_device();
// Exchange hostname and device bus ID
struct DevInfo {
// NOLINTNEXTLINE
char hostname[HOST_NAME_MAX + 1];
int deviceIdx;
};
DevInfo devInfo{};
gethostname(devInfo.hostname, sizeof(devInfo.hostname));
devInfo.deviceIdx = deviceIdx_;
auto peerDevInfos =
storeAllGather(store_, "handshake-0", rank_, worldSize_, devInfo);
std::vector<int> rankToDeviceIdx;
for (const auto& info : peerDevInfos) {
if (strcmp(info.hostname, peerDevInfos.front().hostname) != 0) {
LOG(WARNING) << "Aborting IntraNodeComm::rendezvous because some "
"participants are not on the same host ("
<< info.hostname << ", " << devInfo.hostname << ")";
return false;
}
rankToDeviceIdx.emplace_back(info.deviceIdx);
}
{
std::unordered_set uniqueDeviceIdxs(
rankToDeviceIdx.begin(), rankToDeviceIdx.end());
if (uniqueDeviceIdxs.size() != worldSize_) {
LOG(WARNING)
<< "Skipping IntraNodeComm::rendezvous() because participants have "
"overlapping devices. To resolve this, call torch.cuda.set_device() "
"before init_process_group().";
return false;
}
}
// Query nvlink connection
auto nvlMesh = getNvlMesh(rankToDeviceIdx);
// Detect topology
topology_ = detectTopology(nvlMesh, worldSize_);
if (topology_ != Topology::FULLY_CONNECTED) {
return false;
}
auto groupName = "IntraNodeComm" + std::to_string(intraNodeCommIdx++);
set_group_info(
groupName, static_cast<int>(rank_), static_cast<int>(worldSize_), store_);
auto allocator = get_allocator(c10::DeviceType::CUDA);
symmetricMemoryPtr_ = allocator->alloc(bufferSize_, deviceIdx_, groupName);
symmetricMemory_ = allocator->rendezvous(symmetricMemoryPtr_, std::nullopt);
isInitialized_ = true;
return true;
#endif
return false;
}
} // namespace c10d::intra_node_comm
|
