add doc for #14386 (#14655)

python/sglang/srt/managers/schedule_batch.py

@@ -360,6 +360,9 @@ class MultimodalInputs:
         ret.mm_items = [item for item in ret.mm_items if item.is_valid()]
 
         if envs.SGLANG_MM_BUFFER_SIZE_MB.get() > 0:
+            # Multi-modal feature hashing optimization:
+            # When SGLANG_MM_BUFFER_SIZE_MB > 0, we temporarily move feature tensors to GPU
+            # for faster hash computation, while avoiding OOM issues.
             from sglang.srt.managers.mm_utils import (
                 init_feature_buffer,
                 is_feature_buffer_initialized,