refactor: PagedCache Facade 模式，提取 PagePool/PrefixCache/TaskTable

- cache.py: 提取 PagePool (位图+LRU)、PrefixCache (前缀哈希)、TaskTable (任务页表)
  PagedCache 降为 Facade 组合三者 + 张量存储，公开 API 不变
- executor.py: 移除 allocate_pages_for_activation/free_task_pages/get_cached_tokens
  三冗余委托方法，去掉 page_size 构造参数(改用 page_cache.page_size)
- scheduler.py: 直接调用 self._page_cache.* 代替已移除的 Executor 委托
- 移除 CacheView.__slots__、PagePool.ref_count、PagedCache.alloc/pages_needed/inc_ref
  PrefixCache.evict 等死/冗余方法

astrai/inference/cache.py

@@ -1,4 +1,5 @@
-from typing import Dict, List, Tuple
+from collections import OrderedDict
+from typing import Callable, Dict, List, Optional, Tuple
 
 import torch
 from torch import Tensor
@@ -13,8 +14,136 @@ def page_hash(token_ids: List[int], page_idx: int, page_size: int) -> int:
     return h
 
 
+class PagePool:
+    """Bitmask page allocator with ref-counting and LRU eviction."""
+
+    def __init__(self, n_pages: int, on_evict: Optional[Callable[[int], None]] = None):
+        self._free_mask = (1 << n_pages) - 1
+        self._refs: List[int] = [0] * n_pages
+        self._lru: OrderedDict[int, None] = OrderedDict()
+        self._on_evict = on_evict
+
+    def alloc(self) -> int:
+        if self._free_mask:
+            lsb = self._free_mask & -self._free_mask
+            idx = lsb.bit_length() - 1
+            self._free_mask ^= lsb
+            self._refs[idx] = 1
+            return idx
+        if self._lru:
+            idx, _ = self._lru.popitem(last=False)
+            if self._on_evict:
+                self._on_evict(idx)
+            self._refs[idx] = 1
+            self._free_mask &= ~(1 << idx)
+            return idx
+        return -1
+
+    def free(self, idx: int, keep_cached: bool = False) -> None:
+        self._refs[idx] -= 1
+        if self._refs[idx] == 0:
+            if keep_cached:
+                self._lru[idx] = None
+            else:
+                self._free_mask |= 1 << idx
+
+    def inc_ref(self, idx: int) -> None:
+        self._refs[idx] += 1
+
+    def touch(self, idx: int) -> None:
+        self._lru.move_to_end(idx)
+
+    def remove_from_lru(self, idx: int) -> None:
+        self._lru.pop(idx, None)
+
+
+class PrefixCache:
+    """Hash-based prefix matching: maps page hashes to physical page indices."""
+
+    def __init__(self, page_size: int):
+        self._page_size = page_size
+        self._page_to_hash: Dict[int, int] = {}
+        self._hash_to_page: Dict[int, int] = {}
+
+    def on_evict(self, idx: int) -> None:
+        h = self._page_to_hash.pop(idx, None)
+        if h is not None:
+            self._hash_to_page.pop(h, None)
+
+    def has_page(self, idx: int) -> bool:
+        return idx in self._page_to_hash
+
+    def lookup(self, token_ids: List[int], pool: PagePool) -> List[int]:
+        full_pages = len(token_ids) // self._page_size
+        hits: List[int] = []
+        for i in range(full_pages):
+            h = page_hash(token_ids, i, self._page_size)
+            p = self._hash_to_page.get(h)
+            if p is None:
+                break
+            pool.touch(p)
+            hits.append(p)
+        return hits
+
+    def record(
+        self,
+        page_idx: int,
+        token_ids: List[int],
+        logical_page_idx: int,
+        pool: PagePool,
+    ) -> None:
+        h = page_hash(token_ids, logical_page_idx, self._page_size)
+        old_h = self._page_to_hash.pop(page_idx, None)
+        if old_h is not None:
+            self._hash_to_page.pop(old_h, None)
+        self._page_to_hash[page_idx] = h
+        self._hash_to_page[h] = page_idx
+        pool.remove_from_lru(page_idx)
+
+
+class TaskTable:
+    """Maps task_ids to page tables and cached token counts."""
+
+    def __init__(self, pool: PagePool, page_size: int):
+        self._pool = pool
+        self._page_size = page_size
+        self._pages: Dict[str, List[int]] = {}
+        self._cached: Dict[str, int] = {}
+
+    def set(self, task_id: str, page_table: List[int], cached: int) -> None:
+        self._pages[task_id] = page_table
+        self._cached[task_id] = cached
+
+    def get(self, task_id: str) -> List[int]:
+        return self._pages.get(task_id, [])
+
+    def get_cached(self, task_id: str) -> int:
+        return self._cached.get(task_id, 0)
+
+    def pop(self, task_id: str) -> Tuple[List[int], int]:
+        pages = self._pages.pop(task_id, [])
+        cached = self._cached.pop(task_id, 0)
+        return pages, cached
+
+    def extend(self, task_id: str, pos: int) -> bool:
+        page_table = self._pages[task_id]
+        needed = (pos + 1 + self._page_size - 1) // self._page_size
+        while len(page_table) < needed:
+            p = self._pool.alloc()
+            if p < 0:
+                return False
+            page_table.append(p)
+        return True
+
+    def table_tensor(self, task_ids: List[str], device: torch.device) -> Tensor:
+        states = [self._pages.get(tid, []) for tid in task_ids]
+        max_pages = max((len(s) for s in states), default=0)
+        rows = [s + [-1] * (max_pages - len(s)) for s in states]
+        return torch.tensor(rows, dtype=torch.long, device=device)
+
+
 class PagedCache:
-    """Paged KV cache: page pool, prefix-cache lookup, LRU eviction, task-page mapping."""
+    """Facade: paged KV-cache backed by PagePool, PrefixCache, and TaskTable."""
 
     def __init__(
         self,
@@ -27,8 +156,10 @@ class PagedCache:
         dtype: torch.dtype,
     ):
         self.page_size = page_size
-        self._free_mask = (1 << n_pages) - 1
+        self._prefix = PrefixCache(page_size)
-        self._refs: List[int] = [0] * n_pages
+        self._pool = PagePool(n_pages, on_evict=self._prefix.on_evict)
+        self._table = TaskTable(self._pool, page_size)
+
         self.k_cache = torch.empty(
             (n_layers, n_pages, page_size, n_kv_heads, head_dim),
             device=device,
@@ -39,160 +170,81 @@ class PagedCache:
             device=device,
             dtype=dtype,
         )
-        self._page_to_hash: Dict[int, int] = {}
-        self._hash_to_page: Dict[int, int] = {}
-        self._lru: List[int] = []
-        self._pin: List[bool] = [False] * n_pages
-        self._task_pages: Dict[str, List[int]] = {}
-        self._task_cached: Dict[str, int] = {}
 
-    def pages_needed(self, n_tokens: int) -> int:
+    def alloc_n(self, n: int) -> List[int]:
-        return (n_tokens + self.page_size - 1) // self.page_size
+        pages: List[int] = []
+        for _ in range(n):
+            p = self._pool.alloc()
+            if p < 0:
+                for page in pages:
+                    self.free(page)
+                return []
+            pages.append(p)
+        return pages
+
+    def free(self, idx: int) -> None:
+        cached = self._prefix.has_page(idx)
+        self._pool.free(idx, keep_cached=cached)
+        if not cached:
+            self._prefix.on_evict(idx)
 
     def task_alloc(self, task_id: str, prompt_ids: List[int]) -> bool:
-        hit_pages = self.lookup_prefix(prompt_ids)
+        hits = self._prefix.lookup(prompt_ids, self._pool)
-        cached_tokens = len(hit_pages) * self.page_size
+        cached = len(hits) * self.page_size
-        for p in hit_pages:
+        for p in hits:
-            self.inc_ref(p)
+            self._pool.inc_ref(p)
 
-        remaining = len(prompt_ids) - cached_tokens
+        remaining = len(prompt_ids) - cached
-        n_new = self.pages_needed(remaining) if remaining > 0 else 0
+        n_new = (
-        new_pages = self.alloc_n(n_new) if n_new > 0 else []
+            (remaining + self.page_size - 1) // self.page_size if remaining > 0 else 0
+        )
+        new_pages: List[int] = []
+        if n_new > 0:
+            for _ in range(n_new):
+                p = self._pool.alloc()
+                if p < 0:
+                    for hp in hits:
+                        self.free(hp)
+                    for np in new_pages:
+                        self.free(np)
+                    return False
+                new_pages.append(p)
 
-        if remaining > 0 and not new_pages:
+        self._table.set(task_id, hits + new_pages, cached)
-            for p in hit_pages:
-                self.free(p)
-            return False
-
-        page_table = hit_pages + new_pages
-        self._task_pages[task_id] = page_table
-        self._task_cached[task_id] = cached_tokens
         return True
 
     def task_free(self, task_id: str) -> None:
-        page_table = self._task_pages.pop(task_id, None)
+        page_table, _ = self._table.pop(task_id)
-        self._task_cached.pop(task_id, None)
+        for idx in page_table:
-        if page_table:
+            self.free(idx)
-            for idx in page_table:
-                self.free(idx)
 
     def task_extend(self, task_id: str, pos: int) -> bool:
-        needed = self.pages_needed(pos + 1)
+        return self._table.extend(task_id, pos)
-        page_table = self._task_pages[task_id]
-        while len(page_table) < needed:
-            p = self.alloc()
-            if p < 0:
-                return False
-            page_table.append(p)
-        return True
 
     def task_cached(self, task_id: str) -> int:
-        return self._task_cached.get(task_id, 0)
+        return self._table.get_cached(task_id)
-
-    def task_page_table(self, task_id: str) -> List[int]:
-        return self._task_pages.get(task_id, [])
-
-    def task_n_pages(self, task_id: str) -> int:
-        return len(self._task_pages.get(task_id, []))
 
     def task_record_hashes(
         self, task_id: str, prompt_ids: List[int], start_logical_page: int = 0
     ) -> None:
-        page_table = self._task_pages[task_id]
+        page_table = self._table.get(task_id)
         full_pages = len(prompt_ids) // self.page_size
         for i in range(start_logical_page, full_pages):
-            self.record_page(page_table[i], prompt_ids, i)
+            self._prefix.record(page_table[i], prompt_ids, i, self._pool)
 
     def make_table_tensor(self, task_ids: List[str], device: torch.device) -> Tensor:
-        states = [self._task_pages.get(tid, []) for tid in task_ids]
+        return self._table.table_tensor(task_ids, device)
-        max_pages = max((len(s) for s in states), default=0)
-        rows = [s + [-1] * (max_pages - len(s)) for s in states]
-        return torch.tensor(rows, dtype=torch.long, device=device)
-
-    def _touch(self, idx: int) -> None:
-        if self._refs[idx] == 0 and idx in self._lru:
-            self._lru.remove(idx)
-            self._lru.append(idx)
-
-    def _evict_one(self) -> int:
-        while self._lru:
-            idx = self._lru.pop(0)
-            h = self._page_to_hash.pop(idx, None)
-            if h is not None:
-                self._hash_to_page.pop(h, None)
-            self._pin[idx] = False
-            self._refs[idx] = 1
-            return idx
-        return -1
-
-    def record_page(
-        self, page_idx: int, token_ids: List[int], logical_page_idx: int
-    ) -> None:
-        h = page_hash(token_ids, logical_page_idx, self.page_size)
-        old_h = self._page_to_hash.pop(page_idx, None)
-        if old_h is not None:
-            self._hash_to_page.pop(old_h, None)
-        self._page_to_hash[page_idx] = h
-        self._hash_to_page[h] = page_idx
-        self._pin[page_idx] = True
-        if page_idx in self._lru:
-            self._lru.remove(page_idx)
-
-    def lookup_prefix(self, token_ids: List[int]) -> List[int]:
-        full_pages = len(token_ids) // self.page_size
-        hits: List[int] = []
-        for i in range(full_pages):
-            h = page_hash(token_ids, i, self.page_size)
-            p = self._hash_to_page.get(h)
-            if p is None:
-                break
-            self._touch(p)
-            hits.append(p)
-        return hits
-
-    def inc_ref(self, idx: int) -> None:
-        self._refs[idx] += 1
-        if self._refs[idx] == 1 and idx in self._lru:
-            self._lru.remove(idx)
-
-    def alloc(self) -> int:
-        if self._free_mask:
-            lsb = self._free_mask & -self._free_mask
-            idx = lsb.bit_length() - 1
-            self._free_mask ^= lsb
-            self._refs[idx] = 1
-            if idx in self._lru:
-                self._lru.remove(idx)
-            return idx
-        return self._evict_one()
-
-    def alloc_n(self, n: int) -> List[int]:
-        pages = [self.alloc() for _ in range(n)]
-        if any(p < 0 for p in pages):
-            for p in pages:
-                if p >= 0:
-                    self.free(p)
-            return []
-        return pages
-
-    def free(self, idx: int) -> None:
-        self._refs[idx] -= 1
-        if self._refs[idx] == 0:
-            h = self._page_to_hash.get(idx)
-            if h is not None and self._pin[idx]:
-                self._lru.append(idx)
-            else:
-                self._free_mask |= 1 << idx
-                h = self._page_to_hash.pop(idx, None)
-                if h is not None:
-                    self._hash_to_page.pop(h, None)
-                self._pin[idx] = False
 
     def bind(self, page_table: Tensor, total_len: int = 0) -> "CacheView":
         return CacheView(self, page_table, total_len)
 
     def write(
-        self, layer_id: int, page_table: Tensor, start_pos: int, k: Tensor, v: Tensor
+        self,
+        layer_id: int,
+        page_table: Tensor,
+        start_pos: int,
+        k: Tensor,
+        v: Tensor,
     ) -> None:
         seq_len = k.size(1)
         if seq_len == 0:
@@ -232,8 +284,6 @@ class PagedCache:
 class CacheView:
     """Bundles PagedCache + page_table + total_len for attention layers."""
 
-    __slots__ = ("_cache", "_page_table", "_total_len")
-
     def __init__(self, cache: PagedCache, page_table: Tensor, total_len: int = 0):
         self._cache = cache
         self._page_table = page_table

astrai/inference/executor.py

@@ -13,33 +13,22 @@ logger = logging.getLogger(__name__)
 
 
 class Executor:
-    """Model forward passes for prefill and decode; delegates page ops to PagedCache."""
+    """Model forward passes for prefill and decode phases."""
 
     def __init__(
         self,
         model: AutoModel,
         tokenizer: AutoTokenizer,
         page_cache: PagedCache,
-        page_size: int = 64,
         device: Optional[str] = None,
         dtype: Optional[torch.dtype] = None,
     ):
         self.model = model
         self.tokenizer = tokenizer
         self.page_cache = page_cache
-        self.page_size = page_size
         self.device = device or next(model.parameters()).device
         self.dtype = dtype or next(model.parameters()).dtype
 
-    def allocate_pages_for_activation(self, task: Task) -> bool:
-        return self.page_cache.task_alloc(task.task_id, task.prompt_ids)
-
-    def free_task_pages(self, task: Task) -> None:
-        self.page_cache.task_free(task.task_id)
-
-    def get_cached_tokens(self, task: Task) -> int:
-        return self.page_cache.task_cached(task.task_id)
-
     def execute_prefill(
         self, tasks: List[Task], prompt_len: int, start_pos: int = 0
     ) -> None:
@@ -71,7 +60,7 @@ class Executor:
                 paged_cache=self.page_cache.bind(page_tables, total_len=prompt_len),
             )
 
-        start_logical_page = start_pos // self.page_size
+        start_logical_page = start_pos // self.page_cache.page_size
         for t in tasks:
             self.page_cache.task_record_hashes(
                 t.task_id, t.prompt_ids, start_logical_page=start_logical_page

astrai/inference/scheduler.py

@@ -33,19 +33,16 @@ class InferenceScheduler:
         self.device = device or next(model.parameters()).device
         self.dtype = dtype or next(model.parameters()).dtype
 
-        n_kv_heads = config.n_kv_heads
-        head_dim = config.dim // config.n_heads
-        n_layers = config.n_layers
         n_pages = (
             max_batch_size * (self.max_seq_len + page_size) + page_size - 1
         ) // page_size
 
-        page_cache = PagedCache(
+        self._page_cache = PagedCache(
-            n_layers,
+            config.n_layers,
             n_pages,
             page_size,
-            n_kv_heads,
+            config.n_kv_heads,
-            head_dim,
+            config.dim // config.n_heads,
             self.device,
             self.dtype,
         )
@@ -60,8 +57,7 @@ class InferenceScheduler:
         self._executor = Executor(
             model=model,
             tokenizer=tokenizer,
-            page_cache=page_cache,
+            page_cache=self._page_cache,
-            page_size=page_size,
             device=self.device,
             dtype=self.dtype,
         )
@@ -73,7 +69,7 @@ class InferenceScheduler:
 
     def remove_task(self, task_id: str) -> None:
         for task in self._task_mgr.remove_task(task_id):
-            self._executor.free_task_pages(task)
+            self._page_cache.task_free(task.task_id)
 
     def get_stats(self) -> Dict[str, Any]:
         return self._task_mgr.get_stats()
@@ -85,7 +81,7 @@ class InferenceScheduler:
                     self._task_mgr.tokenizer.stop_ids
                 )
                 for task in finished:
-                    self._executor.free_task_pages(task)
+                    self._page_cache.task_free(task.task_id)
 
                 available = self._task_mgr.max_batch_size - len(
                     self._task_mgr.active_tasks
@@ -94,7 +90,7 @@ class InferenceScheduler:
                     candidates = self._task_mgr.pull_candidates(available)
                     failed = []
                     for task in candidates:
-                        if self._executor.allocate_pages_for_activation(task):
+                        if self._page_cache.task_alloc(task.task_id, task.prompt_ids):
                             self._task_mgr.activate(task)
                         else:
                             failed.append(task)
@@ -114,7 +110,10 @@ class InferenceScheduler:
 
                     groups: Dict[Tuple[int, int], List[Task]] = {}
                     for t in to_prefill:
-                        key = (len(t.prompt_ids), self._executor.get_cached_tokens(t))
+                        key = (
+                            len(t.prompt_ids),
+                            self._page_cache.task_cached(t.task_id),
+                        )
                         groups.setdefault(key, []).append(t)
 
                     for (prompt_len, start_pos), group in groups.items():