diff --git a/docs/references/environment_variables.md b/docs/references/environment_variables.md
index 8621dcc78e55..a24eac334683 100644
--- a/docs/references/environment_variables.md
+++ b/docs/references/environment_variables.md
@@ -37,6 +37,7 @@ SGLang supports various environment variables that can be used to configure its
 | `SGLANG_SCHEDULER_RECV_SKIPPER_WEIGHT_DECODE` | Weight increment for decode forward mode in scheduler recv skipper. Works with `--scheduler-recv-interval` to control polling frequency during decode phase. | `1` |
 | `SGLANG_SCHEDULER_RECV_SKIPPER_WEIGHT_VERIFY` | Weight increment for target verify forward mode in scheduler recv skipper. Works with `--scheduler-recv-interval` to control polling frequency during verification phase. | `1` |
 | `SGLANG_SCHEDULER_RECV_SKIPPER_WEIGHT_NONE` | Weight increment when forward mode is None in scheduler recv skipper. Works with `--scheduler-recv-interval` to control polling frequency when no specific forward mode is active. | `1` |
+| `SGLANG_MM_BUFFER_SIZE_MB` | Size of preallocated GPU buffer (in MB) for multi-modal feature hashing optimization. When set to a positive value, temporarily moves features to GPU for faster hash computation, then moves them back to CPU to save GPU memory. Larger features benefit more from GPU hashing. Set to `0` to disable. | `0` |
 | `SGLANG_MM_PRECOMPUTE_HASH` | Enable precomputing of hash values for MultimodalDataItem | `false` |
 
 
diff --git a/python/sglang/srt/managers/schedule_batch.py b/python/sglang/srt/managers/schedule_batch.py
index 7bfa712ffd2e..81ce51f7c9d8 100644
--- a/python/sglang/srt/managers/schedule_batch.py
+++ b/python/sglang/srt/managers/schedule_batch.py
@@ -360,6 +360,9 @@ def from_dict(obj: dict):
         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,