[HICache] introduce evict policy (#10190)

Signed-off-by: Xuchun Shang <xuchun.shang@linux.alibaba.com>
Co-authored-by: Teng Ma <sima.mt@alibaba-inc.com>

python/sglang/srt/server_args.py

@@ -185,6 +185,7 @@ class ServerArgs:
     hybrid_kvcache_ratio: Optional[float] = None
     swa_full_tokens_ratio: float = 0.8
     disable_hybrid_swa_memory: bool = False
+    radix_eviction_policy: str = "lru"
 
     # Runtime options
     device: Optional[str] = None
@@ -1907,6 +1908,13 @@ class ServerArgs:
             default=ServerArgs.hicache_write_policy,
             help="The write policy of hierarchical cache.",
         )
+        parser.add_argument(
+            "--radix-eviction-policy",
+            type=str,
+            choices=["lru", "lfu"],
+            default=ServerArgs.radix_eviction_policy,
+            help="The eviction policy of radix trees. 'lru' stands for Least Recently Used, 'lfu' stands for Least Frequently Used.",
+        )
         parser.add_argument(
             "--hicache-io-backend",
             type=str,