add flag to prevent unnessary memory free

paddle/fluid/memory/detail/buddy_allocator.cc

@@ -15,6 +15,10 @@ limitations under the License. */
 #include "paddle/fluid/memory/detail/buddy_allocator.h"
 #include "glog/logging.h"
 
+DEFINE_bool(free_idle_memory, false,
+            "If it is true, Paddle will try to free idle memory trunks during "
+            "running time.");
+
 namespace paddle {
 namespace memory {
 namespace detail {
@@ -152,14 +156,15 @@ void BuddyAllocator::Free(void* p) {
   pool_.insert(
       IndexSizeAddress(block->index(cache_), block->total_size(cache_), block));
 
+  if (FLAGS_free_idle_memory) {
     // Clean up if existing too much free memory
-
     // Prefer freeing fallback allocation first
     CleanIdleFallBackAlloc();
 
     // Free normal allocation
     CleanIdleNormalAlloc();
   }
+}
 
 size_t BuddyAllocator::Used() { return total_used_; }
 

python/paddle/fluid/__init__.py

@@ -123,7 +123,7 @@ def __bootstrap__():
     read_env_flags = [
         'use_pinned_memory', 'check_nan_inf', 'benchmark', 'warpctc_dir',
         'eager_delete_scope', 'use_mkldnn', 'initial_cpu_memory_in_mb',
-        'init_allocated_mem'
+        'init_allocated_mem', 'free_idle_memory'
     ]
     if core.is_compiled_with_dist():
         read_env_flags.append('rpc_deadline')