diff --git a/src/glmtuner/api/app.py b/src/glmtuner/api/app.py
index 63dbd72..ba1fb7d 100644
--- a/src/glmtuner/api/app.py
+++ b/src/glmtuner/api/app.py
@@ -57,7 +57,9 @@ async def create_chat_completion(request: ChatCompletionRequest):
 
         prev_messages = request.messages[:-1]
         if len(prev_messages) > 0 and prev_messages[0].role == Role.SYSTEM:
-            query = prev_messages.pop(0).content + query
+            prefix = prev_messages.pop(0).content
+        else:
+            prefix = None
 
         history = []
         if len(prev_messages) % 2 == 0:
@@ -66,17 +68,17 @@ async def create_chat_completion(request: ChatCompletionRequest):
                     history.append([prev_messages[i].content, prev_messages[i+1].content])
 
         if request.stream:
-            generate = predict(query, history, request)
+            generate = predict(query, history, prefix, request)
             return EventSourceResponse(generate, media_type="text/event-stream")
 
-        response = chat_model.chat(
-            query, history, temperature=request.temperature, top_p=request.top_p, max_new_tokens=request.max_tokens
+        response, (prompt_length, response_length) = chat_model.chat(
+            query, history, prefix, temperature=request.temperature, top_p=request.top_p, max_new_tokens=request.max_tokens
         )
 
-        usage = ChatCompletionResponseUsage( # too complex to compute
-            prompt_tokens=1,
-            completion_tokens=1,
-            total_tokens=2
+        usage = ChatCompletionResponseUsage(
+            prompt_tokens=prompt_length,
+            completion_tokens=response_length,
+            total_tokens=prompt_length+response_length
         )
 
         choice_data = ChatCompletionResponseChoice(
@@ -87,7 +89,7 @@ async def create_chat_completion(request: ChatCompletionRequest):
 
         return ChatCompletionResponse(model=request.model, choices=[choice_data], usage=usage)
 
-    async def predict(query: str, history: List[Tuple[str, str]], request: ChatCompletionRequest):
+    async def predict(query: str, history: List[Tuple[str, str]], prefix: str, request: ChatCompletionRequest):
         choice_data = ChatCompletionResponseStreamChoice(
             index=0,
             delta=DeltaMessage(role=Role.ASSISTANT),
@@ -97,7 +99,7 @@ async def predict(query: str, history: List[Tuple[str, str]], request: ChatCompl
         yield json.dumps(chunk, ensure_ascii=False)
 
         for new_text in chat_model.stream_chat(
-            query, history, temperature=request.temperature, top_p=request.top_p, max_new_tokens=request.max_tokens
+            query, history, prefix, temperature=request.temperature, top_p=request.top_p, max_new_tokens=request.max_tokens
         ):
             if len(new_text) == 0:
                 continue
diff --git a/src/glmtuner/chat/stream_chat.py b/src/glmtuner/chat/stream_chat.py
index d2d3f11..ae56df2 100644
--- a/src/glmtuner/chat/stream_chat.py
+++ b/src/glmtuner/chat/stream_chat.py
@@ -1,8 +1,11 @@
 import torch
 from typing import Any, Dict, Generator, List, Optional, Tuple
+from threading import Thread
+from transformers import TextIteratorStreamer
 
+from glmtuner.extras.misc import get_logits_processor
 from glmtuner.extras.misc import auto_configure_device_map
-from glmtuner.hparams import ModelArguments, FinetuningArguments, GeneratingArguments
+from glmtuner.hparams import ModelArguments, DataArguments, FinetuningArguments, GeneratingArguments
 from glmtuner.tuner import load_model_and_tokenizer
 
 
@@ -11,6 +14,7 @@ class ChatModel:
     def __init__(
         self,
         model_args: ModelArguments,
+        data_args: DataArguments,
         finetuning_args: FinetuningArguments,
         generating_args: GeneratingArguments
     ) -> None:
@@ -23,10 +27,30 @@ def __init__(
         else:
             self.model = self.model.cuda()
 
-        self.model.eval()
+        self.source_prefix = data_args.source_prefix if data_args.source_prefix else ""
         self.generating_args = generating_args
 
-    def process_args(self, **input_kwargs) -> Dict[str, Any]:
+    def get_prompt(
+        self, query: str, history: Optional[List[Tuple[str, str]]] = None, prefix: Optional[str] = None
+    ) -> str:
+        prefix = prefix + "\n" if prefix else "" # add separator for non-empty prefix
+        history = history if history else []
+        prompt = ""
+        for i, (old_query, response) in enumerate(history):
+            prompt += "[Round {}]\n\n问：{}\n\n答：{}\n\n".format(i+1, old_query, response)
+        prompt += "[Round {}]\n\n问：{}\n\n答：".format(len(history)+1, query)
+        prompt = prefix + prompt
+        return prompt
+
+    def process_args(
+        self, query: str, history: Optional[List[Tuple[str, str]]] = None, prefix: Optional[str] = None, **input_kwargs
+    ) -> Tuple[Dict[str, Any], int]:
+        prefix = prefix if prefix else self.source_prefix
+
+        inputs = self.tokenizer([self.get_prompt(query, history, prefix)], return_tensors="pt")
+        inputs = inputs.to(self.model.device)
+        prompt_length = len(inputs["input_ids"][0])
+
         temperature = input_kwargs.pop("temperature", None)
         top_p = input_kwargs.pop("top_p", None)
         top_k = input_kwargs.pop("top_k", None)
@@ -36,10 +60,12 @@ def process_args(self, **input_kwargs) -> Dict[str, Any]:
 
         gen_kwargs = self.generating_args.to_dict()
         gen_kwargs.update(dict(
+            input_ids=inputs["input_ids"],
             temperature=temperature or gen_kwargs["temperature"],
             top_p=top_p or gen_kwargs["top_p"],
             top_k=top_k or gen_kwargs["top_k"],
-            repetition_penalty=repetition_penalty or gen_kwargs["repetition_penalty"]
+            repetition_penalty=repetition_penalty or gen_kwargs["repetition_penalty"],
+            logits_processor=get_logits_processor()
         ))
 
         if max_length:
@@ -50,24 +76,29 @@ def process_args(self, **input_kwargs) -> Dict[str, Any]:
             gen_kwargs.pop("max_length", None)
             gen_kwargs["max_new_tokens"] = max_new_tokens
 
-        return gen_kwargs
+        return gen_kwargs, prompt_length
 
     @torch.inference_mode()
-    def chat(self, query: str, history: Optional[List[Tuple[str, str]]] = None, **input_kwargs) -> str:
-        gen_kwargs = self.process_args(**input_kwargs)
-        response = self.model.chat(self.tokenizer, query, history, **gen_kwargs)
-        return response
+    def chat(
+        self, query: str, history: Optional[List[Tuple[str, str]]] = None, prefix: Optional[str] = None, **input_kwargs
+    ) -> Tuple[str, Tuple[int, int]]:
+        gen_kwargs, prompt_length = self.process_args(query, history, prefix, **input_kwargs)
+        generation_output = self.model.generate(**gen_kwargs)
+        outputs = generation_output.tolist()[0][prompt_length:]
+        response = self.tokenizer.decode(outputs, skip_special_tokens=True)
+        response_length = len(outputs)
+        return response, (prompt_length, response_length)
 
     @torch.inference_mode()
     def stream_chat(
-        self, query: str, history: Optional[List[Tuple[str, str]]] = None, **input_kwargs
+        self, query: str, history: Optional[List[Tuple[str, str]]] = None, prefix: Optional[str] = None, **input_kwargs
     ) -> Generator[str, None, None]:
-        gen_kwargs = self.process_args(**input_kwargs)
-        current_length = 0
-        for new_response, _ in self.model.stream_chat(self.tokenizer, query, history, **gen_kwargs):
-            if len(new_response) == current_length:
-                continue
-
-            new_text = new_response[current_length:]
-            current_length = len(new_response)
+        gen_kwargs, _ = self.process_args(query, history, prefix, **input_kwargs)
+        streamer = TextIteratorStreamer(self.tokenizer, timeout=60.0, skip_prompt=True, skip_special_tokens=True)
+        gen_kwargs["streamer"] = streamer
+
+        thread = Thread(target=self.model.generate, kwargs=gen_kwargs)
+        thread.start()
+
+        for new_text in streamer:
             yield new_text
diff --git a/src/glmtuner/tuner/core/parser.py b/src/glmtuner/tuner/core/parser.py
index 0fa8a8a..409c63d 100644
--- a/src/glmtuner/tuner/core/parser.py
+++ b/src/glmtuner/tuner/core/parser.py
@@ -102,20 +102,20 @@ def get_train_args(
 
 def get_infer_args(
     args: Optional[Dict[str, Any]] = None
-) -> Tuple[ModelArguments, FinetuningArguments, GeneratingArguments]:
+) -> Tuple[ModelArguments, DataArguments, FinetuningArguments, GeneratingArguments]:
 
-    parser = HfArgumentParser((ModelArguments, FinetuningArguments, GeneratingArguments))
+    parser = HfArgumentParser((ModelArguments, DataArguments, FinetuningArguments, GeneratingArguments))
 
     if args is not None:
-        model_args, finetuning_args, generating_args = parser.parse_dict(args)
+        model_args, data_args, finetuning_args, generating_args = parser.parse_dict(args)
     elif len(sys.argv) == 2 and sys.argv[1].endswith(".yaml"):
-        model_args, finetuning_args, generating_args = parser.parse_yaml_file(os.path.abspath(sys.argv[1]))
+        model_args, data_args, finetuning_args, generating_args = parser.parse_yaml_file(os.path.abspath(sys.argv[1]))
     elif len(sys.argv) == 2 and sys.argv[1].endswith(".json"):
-        model_args, finetuning_args, generating_args = parser.parse_json_file(os.path.abspath(sys.argv[1]))
+        model_args, data_args, finetuning_args, generating_args = parser.parse_json_file(os.path.abspath(sys.argv[1]))
     else:
-        model_args, finetuning_args, generating_args = parser.parse_args_into_dataclasses()
+        model_args, data_args, finetuning_args, generating_args = parser.parse_args_into_dataclasses()
 
     assert model_args.checkpoint_dir is None or finetuning_args.finetuning_type == "lora" \
         or len(model_args.checkpoint_dir) == 1, "Only LoRA tuning accepts multiple checkpoints."
 
-    return model_args, finetuning_args, generating_args
+    return model_args, data_args, finetuning_args, generating_args
diff --git a/src/glmtuner/tuner/sft/metric.py b/src/glmtuner/tuner/sft/metric.py
index 541c45c..284c935 100644
--- a/src/glmtuner/tuner/sft/metric.py
+++ b/src/glmtuner/tuner/sft/metric.py
@@ -14,8 +14,6 @@
 class ComputeMetrics:
     r"""
     Wraps the tokenizer into metric functions, used in Seq2SeqTrainerForChatGLM.
-
-    Borrowed from: https://github.com/THUDM/ChatGLM-6B/blob/0c2806fea82683349194e21996dd6b3acc3c265b/ptuning/main.py#L307
     """
 
     tokenizer: PreTrainedTokenizer
@@ -25,7 +23,7 @@ def __call__(self, eval_preds: Sequence[Union[np.ndarray, Tuple[np.ndarray]]]) -
         Uses the model predictions to compute metrics.
         """
         preds, labels = eval_preds
-        score_dict = {"rouge-1": [], "rouge-2": [], "rouge-l": [], "bleu-4": []}
+        score_dict = {"accuracy": [], "rouge-1": [], "rouge-2": [], "rouge-l": [], "bleu-4": []}
 
         preds = np.where(preds != IGNORE_INDEX, preds, self.tokenizer.pad_token_id)
         labels = np.where(labels != IGNORE_INDEX, labels, self.tokenizer.pad_token_id)
@@ -49,5 +47,6 @@ def __call__(self, eval_preds: Sequence[Union[np.ndarray, Tuple[np.ndarray]]]) -
 
             bleu_score = sentence_bleu([list(label)], list(pred), smoothing_function=SmoothingFunction().method3)
             score_dict["bleu-4"].append(round(bleu_score * 100, 4))
+            score_dict["accuracy"].append(float(len(label) != 0 and pred[:len(label)] == label))
 
         return {k: float(np.mean(v)) for k, v in score_dict.items()}
diff --git a/src/glmtuner/webui/chat.py b/src/glmtuner/webui/chat.py
index 5c7d449..2c9e868 100644
--- a/src/glmtuner/webui/chat.py
+++ b/src/glmtuner/webui/chat.py
@@ -76,7 +76,9 @@ def predict(
     ):
         chatbot.append([query, ""])
         response = ""
-        for new_text in self.stream_chat(query, history, max_length=max_length, top_p=top_p, temperature=temperature):
+        for new_text in self.stream_chat(
+            query, history, max_length=max_length, top_p=top_p, temperature=temperature
+        ):
             response += new_text
             new_history = history + [(query, response)]
             chatbot[-1] = [query, response]
diff --git a/src/glmtuner/webui/components/eval.py b/src/glmtuner/webui/components/eval.py
index f681ac3..7fe16e5 100644
--- a/src/glmtuner/webui/components/eval.py
+++ b/src/glmtuner/webui/components/eval.py
@@ -21,8 +21,10 @@ def create_eval_tab(top_elems: Dict[str, Component], runner: Runner) -> Dict[str
     preview_btn.click(get_preview, [dataset_dir, dataset], [preview_count, preview_samples, preview_box])
 
     with gr.Row():
+        max_source_length = gr.Slider(value=512, minimum=3, maximum=4096, step=1)
+        max_target_length = gr.Slider(value=512, minimum=3, maximum=4096, step=1)
         max_samples = gr.Textbox(value="100000")
-        batch_size = gr.Slider(value=8, minimum=1, maximum=128, step=1)
+        batch_size = gr.Slider(value=8, minimum=1, maximum=512, step=1)
         predict = gr.Checkbox(value=True)
 
     with gr.Row():
@@ -42,6 +44,8 @@ def create_eval_tab(top_elems: Dict[str, Component], runner: Runner) -> Dict[str
             top_elems["source_prefix"],
             dataset_dir,
             dataset,
+            max_source_length,
+            max_target_length,
             max_samples,
             batch_size,
             predict
@@ -57,6 +61,8 @@ def create_eval_tab(top_elems: Dict[str, Component], runner: Runner) -> Dict[str
         preview_count=preview_count,
         preview_samples=preview_samples,
         close_btn=close_btn,
+        max_source_length=max_source_length,
+        max_target_length=max_target_length,
         max_samples=max_samples,
         batch_size=batch_size,
         predict=predict,
diff --git a/src/glmtuner/webui/components/sft.py b/src/glmtuner/webui/components/sft.py
index 7bbed7a..a5d83bb 100644
--- a/src/glmtuner/webui/components/sft.py
+++ b/src/glmtuner/webui/components/sft.py
@@ -23,13 +23,15 @@ def create_sft_tab(top_elems: Dict[str, Component], runner: Runner) -> Dict[str,
     preview_btn.click(get_preview, [dataset_dir, dataset], [preview_count, preview_samples, preview_box])
 
     with gr.Row():
+        max_source_length = gr.Slider(value=512, minimum=3, maximum=4096, step=1)
+        max_target_length = gr.Slider(value=512, minimum=3, maximum=4096, step=1)
         learning_rate = gr.Textbox(value="5e-5")
         num_train_epochs = gr.Textbox(value="3.0")
         max_samples = gr.Textbox(value="100000")
 
     with gr.Row():
-        batch_size = gr.Slider(value=4, minimum=1, maximum=128, step=1)
-        gradient_accumulation_steps = gr.Slider(value=4, minimum=1, maximum=32, step=1)
+        batch_size = gr.Slider(value=4, minimum=1, maximum=512, step=1)
+        gradient_accumulation_steps = gr.Slider(value=4, minimum=1, maximum=512, step=1)
         lr_scheduler_type = gr.Dropdown(
             value="cosine", choices=[scheduler.value for scheduler in SchedulerType]
         )
@@ -37,7 +39,7 @@ def create_sft_tab(top_elems: Dict[str, Component], runner: Runner) -> Dict[str,
 
     with gr.Row():
         logging_steps = gr.Slider(value=5, minimum=5, maximum=1000, step=5)
-        save_steps = gr.Slider(value=100, minimum=10, maximum=2000, step=10)
+        save_steps = gr.Slider(value=100, minimum=10, maximum=5000, step=10)
 
     with gr.Row():
         start_btn = gr.Button()
@@ -62,6 +64,8 @@ def create_sft_tab(top_elems: Dict[str, Component], runner: Runner) -> Dict[str,
             top_elems["source_prefix"],
             dataset_dir,
             dataset,
+            max_source_length,
+            max_target_length,
             learning_rate,
             num_train_epochs,
             max_samples,
@@ -88,6 +92,8 @@ def create_sft_tab(top_elems: Dict[str, Component], runner: Runner) -> Dict[str,
         preview_count=preview_count,
         preview_samples=preview_samples,
         close_btn=close_btn,
+        max_source_length=max_source_length,
+        max_target_length=max_target_length,
         learning_rate=learning_rate,
         num_train_epochs=num_train_epochs,
         max_samples=max_samples,
diff --git a/src/glmtuner/webui/locales.py b/src/glmtuner/webui/locales.py
index 398f3c7..cf41496 100644
--- a/src/glmtuner/webui/locales.py
+++ b/src/glmtuner/webui/locales.py
@@ -129,6 +129,26 @@
             "value": "关闭"
         }
     },
+    "max_source_length": {
+        "en": {
+            "label": "Max source length",
+            "info": "Max tokens in source sequence."
+        },
+        "zh": {
+            "label": "输入序列最大长度",
+            "info": "输入序列分词后的最大长度。"
+        }
+    },
+    "max_target_length": {
+        "en": {
+            "label": "Max target length",
+            "info": "Max tokens in target sequence."
+        },
+        "zh": {
+            "label": "输出序列最大长度",
+            "info": "输出序列分词后的最大长度。"
+        }
+    },
     "learning_rate": {
         "en": {
             "label": "Learning rate",
diff --git a/src/glmtuner/webui/runner.py b/src/glmtuner/webui/runner.py
index 8023631..e355f3d 100644
--- a/src/glmtuner/webui/runner.py
+++ b/src/glmtuner/webui/runner.py
@@ -67,6 +67,8 @@ def run_train(
         source_prefix: str,
         dataset_dir: str,
         dataset: List[str],
+        max_source_length: int,
+        max_target_length: int,
         learning_rate: str,
         num_train_epochs: str,
         max_samples: str,
@@ -100,6 +102,8 @@ def run_train(
             source_prefix=source_prefix,
             dataset_dir=dataset_dir,
             dataset=",".join(dataset),
+            max_source_length=max_source_length,
+            max_target_length=max_target_length,
             learning_rate=float(learning_rate),
             num_train_epochs=float(num_train_epochs),
             max_samples=int(max_samples),
@@ -142,6 +146,8 @@ def run_eval(
         source_prefix: str,
         dataset_dir: str,
         dataset: List[str],
+        max_source_length: int,
+        max_target_length: int,
         max_samples: str,
         batch_size: int,
         predict: bool
@@ -171,6 +177,8 @@ def run_eval(
             source_prefix=source_prefix,
             dataset_dir=dataset_dir,
             dataset=",".join(dataset),
+            max_source_length=max_source_length,
+            max_target_length=max_target_length,
             max_samples=int(max_samples),
             per_device_eval_batch_size=batch_size,
             output_dir=output_dir