Clarify "--data-directory" flag (triton-inference-server#587)

* Clarify "--data-directory" flag

* User provided data must match expected byte size

src/clients/c++/concurrency_manager.cc

@@ -270,12 +270,12 @@ ConcurrencyManager::PrepareInfer(
     // if available, use provided data instead
     auto it = input_data_.find(input->Name());
     if (it != input_data_.end()) {
-      if (batch1_size > it->second.size()) {
+      if (batch1_size != it->second.size()) {
         return nic::Error(
             ni::RequestStatusCode::INVALID_ARG,
             "input '" + input->Name() + "' requires " +
                 std::to_string(batch1_size) +
-                " bytes for each batch, but provided data only has " +
+                " bytes for each batch, but provided data has " +
                 std::to_string(it->second.size()) + " bytes");
       }
       data = (const uint8_t*)&(it->second)[0];

src/clients/c++/perf_client.cc

@@ -367,7 +367,9 @@ Usage(char** argv, const std::string& msg = std::string())
       << " be a binary file for each input required by the model."
       << " The file must be named the same as the input and must contain data"
       << " required for sending the input in a batch-1 request. The perf client"
-      << " will reuse the data to match the specified batch size." << std::endl;
+      << " will reuse the data to match the specified batch size."
+      << " Note that the files should contain only the raw binary"
+      << " representation of the data in row major order." << std::endl;
 
   exit(1);
 }