not use shm cache default (#50089)

paddle/phi/core/flags.cc

@@ -1198,11 +1198,11 @@ PADDLE_DEFINE_EXPORTED_bool(trt_ibuilder_cache,
  * mmap_allocator related FLAG
  * Name: use_shm_cache
  * Since Version: 2.5.0
- * Value Range: bool, default=true
+ * Value Range: bool, default=false
  * Example:
  * Note: . If True, mmap_allocator will cache shm file to decrease munmap
  * operation.
  */
 PADDLE_DEFINE_EXPORTED_bool(use_shm_cache,
-                            true,
+                            false,
                             "Use shm cache in mmap_allocator.");

python/paddle/fluid/dataloader/dataloader_iter.py

@@ -410,13 +410,22 @@ class _DataLoaderIterMultiProcess(_DataLoaderIterBase):
         # Note(zhangbo): shm_buffer_size is used for MemoryMapAllocationPool.
         # MemoryMapAllocationPool is used to cache and reuse shm, thus reducing munmap in dataloader.
         # For more details, please see: paddle/fluid/memory/allocation/mmap_allocator.h
-        try:
-            self._worker_shm_buffer_size = (2 + 1) * len(self._dataset[0])
-        except:
+        if os.environ.get('FLAGS_use_shm_cache', False) in [
+            1,
+            '1',
+            True,
+            'True',
+            'true',
+        ]:
+            try:
+                self._worker_shm_buffer_size = (2 + 1) * len(self._dataset[0])
+            except:
+                self._worker_shm_buffer_size = 0
+                warnings.warn(
+                    "Setting the shm cache buffer size to 0, equivalent to not using the shm cache policy."
+                )
+        else:
             self._worker_shm_buffer_size = 0
-            warnings.warn(
-                "Setting the shm cache buffer size to 0, equivalent to not using the shm cache policy."
-            )
         self._main_thread_shm_buffer_size = (
             (self._worker_shm_buffer_size) * 2 * self._num_workers
         )