Clarify ResetDevice operates on all devices associated with backend.

Change: 144258290

tensorflow/compiler/xla/service/backend.cc

@@ -234,4 +234,8 @@ StatusOr<bool> Backend::devices_equivalent(int device_ordinal_a,
           executor_b->GetDeviceDescription().name());
 }
 
+Status Backend::ResetDevices() {
+  return transfer_manager_->ResetDevices(stream_executors_);
+}
+
 }  // namespace xla

tensorflow/compiler/xla/service/backend.h

@@ -149,6 +149,9 @@ class Backend {
   // used for scheduling work. For other platforms, returns NULL.
   const Eigen::ThreadPoolDevice* eigen_intra_op_thread_pool_device() const;
 
+  // Resets the devices associated with this backend.
+  Status ResetDevices();
+
  private:
   struct EigenThreadPoolWrapper;
   Backend(int64 replica_count, perftools::gputools::Platform* platform,

tensorflow/compiler/xla/service/generic_transfer_manager.cc

@@ -160,7 +160,9 @@ Status GenericTransferManager::TransferLiteralToInfeed(
   return Unimplemented("Infeed is not supported on GPU (b/30467474)");
 }
 
-Status GenericTransferManager::ResetDevice(se::StreamExecutor* executor) {
+Status GenericTransferManager::ResetDevices(
+    tensorflow::gtl::ArraySlice<perftools::gputools::StreamExecutor*>
+        executors) {
   return Unimplemented(
       "Device reset is not yet supported on CPU and GPU (b/30481585)");
 }

tensorflow/compiler/xla/service/generic_transfer_manager.h

@@ -55,7 +55,9 @@ class GenericTransferManager : public TransferManager {
   Status TransferLiteralToInfeed(perftools::gputools::StreamExecutor* executor,
                                  const Literal& literal) override;
 
-  Status ResetDevice(perftools::gputools::StreamExecutor* executor) override;
+  Status ResetDevices(
+      tensorflow::gtl::ArraySlice<perftools::gputools::StreamExecutor*>
+          executors) override;
 
   StatusOr<std::vector<perftools::gputools::DeviceMemoryBase>>
   ShallowCopyTupleFromDevice(

tensorflow/compiler/xla/service/service.cc

@@ -1019,16 +1019,7 @@ tensorflow::Status Service::TransferToInfeed(const TransferToInfeedRequest* arg,
 
 tensorflow::Status Service::ResetDevice(const ResetDeviceRequest* arg,
                                         ResetDeviceResponse* result) {
-  int first_device_ordinal = arg->has_device_handle()
-                                 ? arg->device_handle().handle()
-                                 : execute_backend_->default_device_ordinal();
-  TF_ASSIGN_OR_RETURN(auto executors,
-                      execute_backend_->Replicas(first_device_ordinal));
-  for (se::StreamExecutor* executor : executors) {
-    TF_RETURN_IF_ERROR(
-        execute_backend_->transfer_manager()->ResetDevice(executor));
-  }
-  return tensorflow::Status::OK();
+  return execute_backend_->ResetDevices();
 }
 
 tensorflow::Status Service::TransferToClientInProcess(

tensorflow/compiler/xla/service/service.h

@@ -162,7 +162,15 @@ class Service : public ServiceInterface {
       const TransferToInfeedRequest* arg,
       TransferToInfeedResponse* result) override;
 
-  // Resets the device, clearing all existing state on the device.
+  // Resets devices, clearing all existing state on all the devices associated
+  // with this service (including memory allocated on the devices).
+  //
+  // ResetDevice may only be called where no previous Execution state on the
+  // device is used by the next Execution.
+  //
+  // ResetDevice should be called before an Execution that expect the device to
+  // be in the reset state. For example, if the prior Execution modifies device
+  // state (e.g., architectural state) that the next Execution depends on.
   tensorflow::Status ResetDevice(const ResetDeviceRequest* arg,
                                  ResetDeviceResponse* result) override;
 

tensorflow/compiler/xla/service/transfer_manager.h

@@ -23,6 +23,7 @@ limitations under the License.
 #include "tensorflow/compiler/xla/statusor.h"
 #include "tensorflow/compiler/xla/types.h"
 #include "tensorflow/compiler/xla/xla_data.pb.h"
+#include "tensorflow/core/lib/gtl/array_slice.h"
 #include "tensorflow/core/platform/mutex.h"
 #include "tensorflow/core/platform/stream_executor_no_cuda.h"
 #include "tensorflow/core/platform/thread_annotations.h"
@@ -63,8 +64,10 @@ class TransferManager {
       perftools::gputools::StreamExecutor* executor,
       const Literal& literal) = 0;
 
-  // Resets the device that the given executor runs on.
-  virtual Status ResetDevice(perftools::gputools::StreamExecutor* executor) = 0;
+  // Resets the devices associated with this transfer manager.
+  virtual Status ResetDevices(
+      tensorflow::gtl::ArraySlice<perftools::gputools::StreamExecutor*>
+          executor) = 0;
 
   // Shallow copy a tuple from the device and create a DeviceMemoryBase object
   // for each element in the tuple. A DeviceMemoryBase object refers to the