refine with comments

test=develop

paddle/fluid/framework/ir/runtime_context_cache_pass.cc

@@ -25,7 +25,7 @@ std::unique_ptr<ir::Graph> RuntimeContextCachePass::ApplyImpl(
   VLOG(3) << "Applies Runtime Context Cache strategy.";
   for (const Node* n : graph->Nodes()) {
     if (n->IsOp()) {
-      n->Op()->SetAttr(kEnableRuntimeContext, true);
+      n->Op()->SetAttr(kEnableCacheRuntimeContext, true);
     }
   }
   return graph;

paddle/fluid/framework/operator.cc

@@ -876,7 +876,7 @@ std::vector<KernelConfig>* OperatorWithKernel::GetKernelConfig(
 
 RuntimeContext* OperatorWithKernel::GetRuntimeContext(
     const Scope& scope) const {
-  if (!HasAttr(kEnableRuntimeContext)) {
+  if (!HasAttr(kEnableCacheRuntimeContext)) {
     return new RuntimeContext(Inputs(), Outputs(), scope);
   } else {
     const Scope* cur_scope = &scope;

paddle/fluid/framework/operator.h

@@ -63,12 +63,12 @@ constexpr char kZeroVarSuffix[] = "@ZERO";
 constexpr char kNewGradSuffix[] = "@NEWGRAD@";
 
 /// RuntimeContext is used to relate input/output names of Operator with
-/// the corresponding variables in Scope.
-/// If an Op has attribute kEnableRuntimeContext, it means that in a same Scope,
-/// since the input/output names of this Op do not change in the execution,
-/// RuntimeContext could be created only at the first iteration of this Op's
-/// execution to save the elapsed time.
-constexpr char kEnableRuntimeContext[] = "@ENABLE_RUNTIME_CONTEXT@";
+/// the corresponding variables in name scope.
+/// If an Op has attribute kEnableCacheRuntimeContext, it means that in a same
+/// name scope, since the input/output names of this Op do not change in the
+/// execution, RuntimeContext could be created only at the first iteration of
+/// this Op's execution to save the elapsed time.
+constexpr char kEnableCacheRuntimeContext[] = "@ENABLE_CACHE_RUNTIME_CONTEXT@";
 
 /// If an Op has this attribute, all its kernels should calculate output
 /// variable's shape in the corresponding Compute() function. And