[v1][Bugfix] Add extra_keys to block_hash for prefix caching (vllm-pr…

…oject#12603)

This pr adds extra key to block hash, to generate different hash value
for two blocks with the same token string but different extra_keys in
their parent blocks. For example, it can generate different hash value
for the second block of the following two requests:
```python
request1 = make_request(
        request_id=0,
        prompt_token_ids=[_ for _ in range(6)],
        mm_positions=[{
            "offset": 0,
            "length": 3
        }, {
            "offset": 3,
            "length": 3
        }],
        mm_hashes=["hash1", "hash2"],
    )
    request2 = make_request(
        request_id=1,
        prompt_token_ids=[_ for _ in range(6)],
        mm_positions=[{
            "offset": 0,
            "length": 3
        }, {
            "offset": 3,
            "length": 3
        }],
        mm_hashes=["hash3", "hash2"],
    )
```

---------

Signed-off-by: Chen Zhang <zhangch99@outlook.com>
Signed-off-by: Isotr0py <2037008807@qq.com>

tests/v1/core/test_kv_cache_utils.py

@@ -192,7 +192,7 @@ def test_hash_block_tokens():
                                    extra_keys)
     assert isinstance(block_hash, BlockHashType)
     assert block_hash.hash_value == hash(
-        (parent_block_hash, *curr_block_token_ids))
+        (parent_block_hash, curr_block_token_ids, extra_keys))
     assert block_hash.token_ids == curr_block_token_ids
     assert block_hash.extra_keys == extra_keys
 
@@ -227,6 +227,38 @@ def test_hash_request_tokens():
     assert block_hashes[1].extra_keys == ("hash2", )
 
 
+def test_hash_tokens_different_mm_input():
+    request1 = make_request(
+        request_id=0,
+        prompt_token_ids=[_ for _ in range(6)],
+        mm_positions=[{
+            "offset": 0,
+            "length": 3
+        }, {
+            "offset": 3,
+            "length": 3
+        }],
+        mm_hashes=["hash1", "hash2"],
+    )
+    request2 = make_request(
+        request_id=1,
+        prompt_token_ids=[_ for _ in range(6)],
+        mm_positions=[{
+            "offset": 0,
+            "length": 3
+        }, {
+            "offset": 3,
+            "length": 3
+        }],
+        mm_hashes=["hash3", "hash2"],
+    )
+    block_size = 3
+    block_hashes1 = hash_request_tokens(block_size, request1)
+    block_hashes2 = hash_request_tokens(block_size, request2)
+    assert block_hashes1[0] != block_hashes2[0]
+    assert block_hashes1[1] != block_hashes2[1]
+
+
 def test_hash_request_tokens_no_mm_inputs():
     request = make_request(
         request_id=0,

vllm/v1/core/kv_cache_utils.py

@@ -262,8 +262,10 @@ def hash_block_tokens(
         The hash value of the block and the token ids in the block.
         The entire tuple is used as the hash key of the block.
     """
-    return BlockHashType(hash((parent_block_hash, *curr_block_token_ids)),
-                         tuple(curr_block_token_ids), extra_keys)
+    curr_block_token_ids_tuple = tuple(curr_block_token_ids)
+    return BlockHashType(
+        hash((parent_block_hash, curr_block_token_ids_tuple, extra_keys)),
+        curr_block_token_ids_tuple, extra_keys)
 
 
 def hash_request_tokens(block_size: int,