fix global_step error in multi-cases

mindspore/ccsrc/backend/optimizer/mem_reuse/mem_dynamic_allocator.h

@@ -87,6 +87,7 @@ class DynamicMemPoolBestFit {
   void ReleaseDeviceRes();
   // Display the information of memory block and memory buf.
   void DumpDynamicMemPoolInfo();
+  SizeMapMemBuf GetIdleMemBufMap() { return global_idle_mem_buf_map_; }
 
   // Get the related memory statistics information.
   size_t total_mem_statistics() const { return total_mem_statistics_; }

mindspore/ccsrc/backend/session/ascend_session.h

@@ -29,6 +29,7 @@
 #include "backend/kernel_compiler/kernel.h"
 #include "backend/session/session_factory.h"
 #include "backend/session/ascend_control_parser.h"
+#include "runtime/device/ascend/ascend_memory_pool.h"
 
 namespace mindspore {
 namespace session {
@@ -37,7 +38,7 @@ enum GraphType : int { COMMON_GRAPH = 0, CONDITION_GRAPH = 1, BRANCH_START = 2,
 class AscendSession : public SessionBasic {
  public:
   AscendSession() { final_graph_id_ = kInvalidGraphId; }
-  ~AscendSession() override = default;
+  ~AscendSession() override { mindspore::device::ascend::AscendMemoryPool::GetInstance().ResetIdleMemBuf(); }
   void Init(uint32_t device_id) override {
     SessionBasic::Init(device_id);
     context_ = std::make_shared<Context>(kAscendDevice, device_id);

mindspore/ccsrc/runtime/device/ascend/ascend_memory_pool.cc

@@ -43,6 +43,13 @@ bool AscendMemoryPool::FreeDeviceMem(const DeviceMemPtr &addr) {
   return true;
 }
 
+void AscendMemoryPool::ResetIdleMemBuf() {
+  auto idle_mem_buf_map = DynamicMemPoolBestFit::GetIdleMemBufMap();
+  for (auto &it : idle_mem_buf_map) {
+    rtMemset(it.second->device_addr_, it.first, 0, it.first);
+  }
+}
+
 size_t AscendMemoryPool::AlignMemorySize(size_t size) const {
   if (size == 0) {
     MS_LOG(EXCEPTION) << "The align memory size is a zero !";

mindspore/ccsrc/runtime/device/ascend/ascend_memory_pool.h

@@ -31,6 +31,7 @@ class AscendMemoryPool : public DynamicMemPoolBestFit {
 
   size_t AllocDeviceMem(size_t size, DeviceMemPtr *addr) override;
   bool FreeDeviceMem(const DeviceMemPtr &addr) override;
+  void ResetIdleMemBuf();
   void set_device_mem_size(uint64_t device_mem_size);
   void set_device_mem_pool_base(uint8_t *device_mem_pool_base);
   void set_device_mem_pool_offset(uint64_t device_mem_pool_offset);