!22327 dataset add shared memory note

Merge pull request !22327 from xiefangqi/md_add_shared_memory_note

mindspore/dataset/core/config.py

@@ -448,6 +448,9 @@ def set_enable_shared_mem(enable):
     """
     if not isinstance(enable, bool):
         raise TypeError("enable must be of type bool.")
+    logger.warning("The shared memory is on, multiprocessing performance will be improved. "
+                   "Note: the required shared memory can't exceeds 80% of the available shared memory. "
+                   "You can reduce max_rowsize or reduce num_parallel_workers to reduce shared memory usage.")
     _config.set_enable_shared_mem(enable)
 
 

mindspore/dataset/engine/datasets.py

@@ -3582,6 +3582,7 @@ def _check_shm_usage(num_worker, queue_size, max_rowsize, num_queues=1):
             if shm_estimate_usage >= threshold_ratio * shm_available:
                 raise RuntimeError(
                     "Insufficient shared memory available. Required: {}, Available: {}. "
+                    "The required memory can't exceed 80% of the available shared memory. "
                     "Recommend to set_enable_shared_mem to False, reduce max_rowsize or reduce num_parallel_workers."
                     .format(shm_estimate_usage, shm_available))
         except FileNotFoundError: