[Bug Fix] Fix mm performance degradation (#3942)

* [Bug Fix] Fix mm performance degradation

* formate

---------

Co-authored-by: Jiang-Jia-Jun <163579578+Jiang-Jia-Jun@users.noreply.github.com>
Co-authored-by: chenjian <1435317881@qq.com>

Author: 3 people

fastdeploy/engine/common_engine.py

@@ -527,8 +527,14 @@ def _fetch_request():
                 self.cfg.max_prefill_batch,
             )
 
+            if self.cfg.model_config.enable_mm:
+                self.resource_manager.check_and_free_block_tables()
+                available_blocks = self.resource_manager.available_block_num()
+            else:
+                available_blocks = self.cfg.cache_config.max_block_num_per_seq
+
             tasks = self.scheduler.get_requests(
-                available_blocks=self.cfg.cache_config.max_block_num_per_seq,
+                available_blocks=available_blocks,
                 block_size=self.cfg.cache_config.block_size,
                 reserved_output_blocks=self.cfg.cache_config.enc_dec_block_num,
                 max_num_batched_tokens=self.cfg.max_model_len,