Evict swa kv cache during decoding (#17220)

python/sglang/srt/mem_cache/chunk_cache.py

@@ -84,62 +84,20 @@ class ChunkCache(BasePrefixCache):
 
 
 class SWAChunkCache(ChunkCache):
-    """ChunkCache with support for hybrid KV cache operations."""
+    """ChunkCache with support for sliding window attention."""
 
-    def __init__(self, params: CacheInitParams):
+    def __init__(self, params: CacheInitParams, sliding_window_size: int):
         assert isinstance(params.token_to_kv_pool_allocator, SWATokenToKVPoolAllocator)
         super().__init__(params)
 
-        assert (
-            params.sliding_window_size is not None
-            or params.attention_chunk_size is not None
-        ), "Sliding window size or attention chunk size must be set for SWAChunkCache"
-
-        if (
-            params.sliding_window_size is not None
-            and params.attention_chunk_size is not None
-        ):
-            logger.warning(
-                "Sliding window size and attention chunk size are both set, use sliding window size for chunk cache eviction."
-            )
-
-        self.sliding_window_size = params.sliding_window_size
-        self.attention_chunk_size = params.attention_chunk_size
-        self.window_size = self.sliding_window_size or self.attention_chunk_size
-
+        self.sliding_window_size = sliding_window_size
         self.chunked_prefill_size = params.chunked_prefill_size
 
     def supports_swa(self) -> bool:
+        assert (
+            self.sliding_window_size is not None
+        ), "sliding_window_size must be set for SWAChunkCache"
         return True
 
-    def evict_swa(
-        self,
-        req: Req,
-        prelen: int,
-    ):
-        if self.sliding_window_size is not None:
-            # Sliding window attention (e.g. mimo-v2-flash, gpt-oss)
-            new_evicted_seqlen_local = max(
-                req.evicted_seqlen_local, prelen - self.sliding_window_size
-            )
-        elif self.attention_chunk_size is not None:
-            # Local attention (e.g. llama4)
-            new_evicted_seqlen_local = max(
-                req.evicted_seqlen_local,
-                prelen // self.attention_chunk_size * self.attention_chunk_size,
-            )
-
-        if self.page_size > 1:
-            new_evicted_seqlen_local = (
-                new_evicted_seqlen_local // self.page_size
-            ) * self.page_size
-
-        if new_evicted_seqlen_local > req.evicted_seqlen_local:
-            free_slots = self.req_to_token_pool.req_to_token[
-                req.req_pool_idx, req.evicted_seqlen_local : new_evicted_seqlen_local
-            ]
-            self.token_to_kv_pool_allocator.free_swa(free_slots)
-            req.evicted_seqlen_local = new_evicted_seqlen_local
-
     def evict(self, num_tokens: int):
         pass