[HiCache] Configurable and Dynamic Prefetch Timeout (#10512)

Co-authored-by: Zhiqiang Xie <xiezhq@stanford.edu>

python/sglang/srt/managers/cache_controller.py

@@ -250,7 +250,7 @@ class HiCacheController:
         storage_backend: Optional[str] = None,
         prefetch_threshold: int = 256,
         model_name: Optional[str] = None,
-        storage_backend_extra_config: Optional[str] = None,
+        storage_backend_extra_config: Optional[dict] = None,
     ):
         self.mem_pool_device_allocator = token_to_kv_pool_allocator
         self.mem_pool_device = token_to_kv_pool_allocator.get_kvcache()
@@ -361,7 +361,7 @@ class HiCacheController:
     def _generate_storage_config(
         self,
         model_name: Optional[str] = None,
-        storage_backend_extra_config: Optional[str] = None,
+        storage_backend_extra_config: Optional[dict] = None,
     ):
 
         if is_dp_attention_enabled():
@@ -376,23 +376,13 @@ class HiCacheController:
         # Currently, AscendMLAPagedTokenToKVPool is the subclass of MLATokenToKVPool.
         is_mla_backend = isinstance(self.mem_pool_device, MLATokenToKVPool)
 
-        # Parse extra config JSON if provided
-        extra_config = None
-        if storage_backend_extra_config:
-            try:
-                import json
-
-                extra_config = json.loads(storage_backend_extra_config)
-            except Exception as e:
-                logger.error(f"Invalid backend extra config JSON: {e}")
-
         return HiCacheStorageConfig(
             tp_rank=self.tp_rank,
             tp_size=self.tp_size,
             is_mla_model=is_mla_backend,
             is_page_first_layout=self.mem_pool_host.layout == "page_first",
             model_name=model_name,
-            extra_config=extra_config,
+            extra_config=storage_backend_extra_config,
         )
 
     def reset(self):

python/sglang/srt/mem_cache/hiradix_cache.py

@@ -1,8 +1,8 @@
 import heapq
+import json
 import logging
 import threading
 import time
-from queue import Queue
 from typing import List, Optional
 
 import torch
@@ -78,9 +78,19 @@ class HiRadixCache(RadixCache):
         self.enable_storage = hicache_storage_backend is not None
         self.enable_storage_metrics = self.enable_storage and enable_metrics
 
-        # todo: customizable storage prefetch threshold and timeout
-        self.prefetch_threshold = 256
-        self.prefetch_timeout = 3  # seconds
+        (
+            extra_config,
+            prefetch_threshold,
+            prefetch_timeout_base,
+            prefetch_timeout_per_ki_token,
+        ) = self._parse_storage_backend_extra_config(storage_backend_extra_config)
+        self.prefetch_threshold = prefetch_threshold
+        self.prefetch_timeout_base = prefetch_timeout_base
+        self.prefetch_timeout_per_page = (
+            page_size / 1024 * prefetch_timeout_per_ki_token
+        )
+        # TODO: support more timeout check functions
+        self.is_prefetch_timeout = self._prefetch_timeout_check_linear_func
         self.prefetch_stop_policy = hicache_storage_prefetch_policy
 
         self.load_cache_event = threading.Event()
@@ -95,7 +105,7 @@ class HiRadixCache(RadixCache):
             storage_backend=hicache_storage_backend,
             prefetch_threshold=self.prefetch_threshold,
             model_name=model_name,
-            storage_backend_extra_config=storage_backend_extra_config,
+            storage_backend_extra_config=extra_config,
         )
         if self.enable_storage_metrics:
             # TODO: support pp
@@ -127,6 +137,53 @@ class HiRadixCache(RadixCache):
             eviction_policy=eviction_policy,
         )
 
+    def _parse_storage_backend_extra_config(
+        self, storage_backend_extra_config: Optional[str]
+    ):
+        """
+        Parse storage backend extra config JSON and extract specific parameters.
+
+        Args:
+            storage_backend_extra_config: JSON string containing extra configuration
+
+        Returns:
+            tuple: (extra_config_dict, prefetch_threshold, prefetch_timeout_base, prefetch_timeout_per_ki_token)
+        """
+        # Parse extra config JSON if provided
+        extra_config = {}
+        if storage_backend_extra_config:
+            try:
+                extra_config = json.loads(storage_backend_extra_config)
+            except Exception as e:
+                logger.error(f"Invalid backend extra config JSON: {e}")
+                raise e
+
+        prefetch_threshold = extra_config.pop("prefetch_threshold", 256)  # tokens
+        prefetch_timeout_base = extra_config.pop("prefetch_timeout_base", 1)  # seconds
+        prefetch_timeout_per_ki_token = extra_config.pop(
+            "prefetch_timeout_per_ki_token", 0.25
+        )  # seconds per 1024 tokens
+
+        if not isinstance(prefetch_threshold, int):
+            raise ValueError(
+                f"prefetch_threshold must be int, got {type(prefetch_threshold).__name__}"
+            )
+        if not isinstance(prefetch_timeout_base, (int, float)):
+            raise ValueError(
+                f"prefetch_timeout_base must be number, got {type(prefetch_timeout_base).__name__}"
+            )
+        if not isinstance(prefetch_timeout_per_ki_token, (int, float)):
+            raise ValueError(
+                f"prefetch_timeout_per_ki_token must be number, got {type(prefetch_timeout_per_ki_token).__name__}"
+            )
+
+        return (
+            extra_config,
+            prefetch_threshold,
+            float(prefetch_timeout_base),
+            float(prefetch_timeout_per_ki_token),
+        )
+
     def reset(self):
         TreeNode.counter = 0
         self.cache_controller.reset()
@@ -490,6 +547,15 @@ class HiRadixCache(RadixCache):
             host_indices = torch.cat(host_indices_list, dim=0)
             cc.mem_pool_host.free(host_indices)
 
+    # Timeout is linearly increasing with the number of pages
+    def _prefetch_timeout_check_linear_func(self, operation: PrefetchOperation):
+        # If hash_value has not been computed in timeout_base seconds, terminate it.
+        return (
+            time.monotonic() - operation.start_time
+            > self.prefetch_timeout_base
+            + len(operation.hash_value) * self.prefetch_timeout_per_page
+        )
+
     def can_terminate_prefetch(self, operation: PrefetchOperation):
         can_terminate = True
 
@@ -506,9 +572,7 @@ class HiRadixCache(RadixCache):
         if self.prefetch_stop_policy == "wait_complete":
             can_terminate = completed
         elif self.prefetch_stop_policy == "timeout":
-            can_terminate = completed or (
-                time.monotonic() - operation.start_time > self.prefetch_timeout
-            )
+            can_terminate = completed or self.is_prefetch_timeout(operation)
         else:
             # unknown prefetch stop policy, just return True
             return True