ipc: patch RDMAVan IPC transport with BYTEPS_ENCODING_SCHEME_VERSION (dmlc#102)

* ipc: patch RDMAVan IPC transport with BYTEPS_ENCODING_SCHEME_VERSION

* fix lint

Author: eric-haibin-lin

src/rdma_transport.h

@@ -521,6 +521,9 @@ class IPCTransport : public RDMATransport {
     val = Environment::Get()->find("BYTEPS_PARTITION_BYTES");
     byteps_partition_bytes_ = val ? atoi(val) : 4096000;
 
+    val = Environment::Get()->find("BYTEPS_ENCODING_SCHEME_VERSION");
+    encoding_scheme_version_ = val ? atoi(val) : 0;
+
     val = Environment::Get()->find("BYTEPS_LOCAL_SIZE");
     auto byteps_local_size = val ? atoi(val) : 8;
     byteps_partition_bytes_ = RoundUp(
@@ -637,6 +640,24 @@ class IPCTransport : public RDMATransport {
     std::lock_guard<std::mutex> lock(shm_mu_);
     auto worker_key = DecodeWorkerKey(key);
     auto seq_num = worker_key % (1 << 16);
+    // Total key space is [0, 2^64 - 1]
+    // It will be divided to N PS servers, for now we assume N <= 2^16
+    // Then we have 2^48 key space left.
+    // Encoding scheme version 0:
+    //   Then we have 2^48 key space left (top 16 bits for different servers)
+    //   MXNet server has a bug dealing with keys larger than 2^32
+    //   Below we support up to 2^16 tensors, and up to 2^16 partitions per
+    //   tensor
+    // Encoding scheme version 1:
+    //   Top 16 bits out of the 48 bits encodes the sender rank
+    //   Mid 16 bits out of the 48 bits encodes the tensor id
+    //   The next 6 bits encodes request types (pushpull, send, etc)
+    //   The last 10 bits encodes the partition id
+    //   Therefore, we support up to 2^16 tensors, and up to 2^10 partitions per
+    //   tensor
+    if (encoding_scheme_version_ == 1) {
+      seq_num = worker_key % (1 << 10);
+    }
     auto base_key = worker_key - seq_num;
     uint64_t offset = byteps_partition_bytes_ * seq_num;
     if (key_shm_addr_.find(base_key) != key_shm_addr_.end()) {
@@ -657,8 +678,8 @@ class IPCTransport : public RDMATransport {
     CHECK_NE(base_ptr, (void *)-1) << strerror(errno);
     key_shm_addr_[base_key] = base_ptr;
 
-    PS_VLOG(1) << "open Shared Memory: " << shm_name << ", offset=" << offset
-               << ", (in bytes) size=" << total_shm_size;
+    PS_VLOG(1) << "open Shared Memory: " << shm_name << " offset=" << offset
+               << " (in bytes) size=" << total_shm_size;
     return (void *)((char *)key_shm_addr_[base_key] + offset);
   }
 
@@ -675,7 +696,7 @@ class IPCTransport : public RDMATransport {
   std::unordered_map<uint64_t, void *> key_shm_addr_;
 
   bool enable_async_copy_;
-
+  int encoding_scheme_version_ = 0;
 };  // class IPCTransport
 
 };  // namespace ps

src/rdma_van.h

@@ -41,8 +41,12 @@ class RDMAVan : public Van {
 
     auto val = Environment::Get()->find("BYTEPS_ENABLE_IPC");
     disable_ipc_ = val ? !atoi(val) : true;
-    if (disable_ipc_) LOG(INFO) << "Shared memory IPC has been disabled";
-
+    if (disable_ipc_) {
+      LOG(INFO) << "Shared memory IPC has been disabled";
+    } else {
+      std::string role = Environment::Get()->find("DMLC_ROLE");
+      CHECK(role != "joint") << "RDMAVan in joint mode does not support IPC";
+    }
     if (event_channel_ == nullptr) {
       event_channel_ = rdma_create_event_channel();
       CHECK(event_channel_) << "Create RDMA event channel failed";