support c4 attn && fix cache

fastdeploy/model_executor/layers/attention/append_attn_backend.py

@@ -18,7 +18,7 @@ from __future__ import annotations
 
 import os
 from dataclasses import dataclass, field
-from typing import TYPE_CHECKING, List, Optional, Tuple
+from typing import TYPE_CHECKING, List, Optional
 
 import paddle
 
@@ -191,16 +191,25 @@ class AppendAttentionBackend(AttentionBackend):
     def get_kv_cache_shape(
         self,
         max_num_blocks: int,
-    ) -> Tuple[int, int, int, int]:
+        kv_cache_quant_type: str = None,
+    ):
         """
         Caculate kv cache shape
         """
-        return (
-            max_num_blocks,
-            self.kv_num_heads,
-            self.block_size,
-            self.head_dim,
-        )
+        if kv_cache_quant_type is not None and kv_cache_quant_type == "int4_zp":
+            return (
+                max_num_blocks,
+                self.kv_num_heads,
+                self.block_size,
+                self.head_dim // 2,
+            )
+        else:
+            return (
+                max_num_blocks,
+                self.kv_num_heads,
+                self.block_size,
+                self.head_dim,
+            )
 
     def forward_mixed(
         self,