refine reallocate of workspace size, test=develop (#19843)

sneaxiy · web-flow · commit 5eb381a3e200 · 2019-09-18T19:14:15.000+08:00
diff --git a/paddle/fluid/platform/device_context.h b/paddle/fluid/platform/device_context.h
@@ -218,6 +218,8 @@ class CudnnWorkspaceHandle {
     if (required_workspace_bytes <= WorkspaceSize()) {
       return;
     }
+    // reset allocation first before re-allocate to save memory
+    allocation_.reset();
     allocation_ = memory::Alloc(device_context_, required_workspace_bytes);
   }
 

Original file line number	Diff line number	Diff line change
`@@ -218,6 +218,8 @@ class CudnnWorkspaceHandle {`
`218`	`218`	`if (required_workspace_bytes <= WorkspaceSize()) {`
`219`	`219`	`return;`
`220`	`220`	`}`
	`221`	`+ // reset allocation first before re-allocate to save memory`
	`222`	`+ allocation_.reset();`
`221`	`223`	`allocation_ = memory::Alloc(device_context_, required_workspace_bytes);`
`222`	`224`	`}`
`223`	`225`