[LLM] vLLM: Add Preempt for scheduler (#9568)

Implement Preempt_by_recompute method for vllm.

python/llm/src/bigdl/llm/vllm/core/scheduler.py

@@ -34,6 +34,7 @@
 # bigdl-llm Intel specified code change
 #
 
+import enum
 import time
 from typing import Dict, Iterable, List, Optional, Tuple, Union
 
@@ -48,6 +49,21 @@ from bigdl.llm.utils.common import invalidInputError
 logger = init_logger(__name__)
 
 
+class PreemptionMode(enum.Enum):
+    """Preemption modes.
+
+    1. Swapping: Swap out the blocks of the preempted sequences to CPU memory
+    and swap them back in when the sequences are resumed.
+    2. Recomputation: Discard the blocks of the preempted sequences and
+    recompute them when the sequences are resumed, treating the sequences as
+    new prompts.
+
+    bigdl: currently only support RECOMPUTE
+    """
+    SWAP = enum.auto()
+    RECOMPUTE = enum.auto()
+
+
 class SchedulerOutputs:
 
     def __init__(
@@ -101,6 +117,7 @@ class FixedWindowScheduler:
         self.cleaned: List[int] = []
         self.kv_cache = kv_cache
         # Co(gc): We no longer have the swapped space as we are not deciding which to swap
+        self.swapped: List[SequenceGroup] = []
         # bigdl-llm change end
 
     def add_seq_group(self, seq_group: SequenceGroup) -> None:
@@ -147,8 +164,9 @@ class FixedWindowScheduler:
         num_curr_seqs = sum(seq_group.get_max_num_running_seqs()
                             for seq_group in self.running)
         num_batched_tokens = 0
+        # logger.info(f"swap: {self.swapped}, wait: {self.waiting}, run: {self.running}")
 
-        if self.waiting:
+        if not self.swapped:
             # We restrict how many requests that can be run using these three arguments
             # Co(gc): If there are waiting requests, we will just try to add it into the
             # running state if not exceeds the stage
@@ -209,6 +227,7 @@ class FixedWindowScheduler:
                 num_curr_seqs += num_new_seqs
                 scheduled.append(seq_group)
 
+            if scheduled or ignored_seq_groups:
                 scheduler_outputs = SchedulerOutputs(
                     scheduled_seq_groups=scheduled,
                     prompt_run=True,
@@ -221,6 +240,57 @@ class FixedWindowScheduler:
         # Now consider all the requests in decoding stage
         self.running = self.policy.sort_by_priority(now, self.running)
 
+        # Reserve new token slots for the running sequence groups.
+        running: List[SequenceGroup] = []
+        preempted: List[SequenceGroup] = []
+        while self.running:
+            seq_group = self.running.pop(0)
+            # while self.seq_ability < 0:
+            #     if self.running:
+            #         # Preempt the lowest-priority sequence groups.
+            #         victim_seq_group = self.running.pop(-1)
+            #         self._preempt(victim_seq_group)
+            #         preempted.append(victim_seq_group)
+            #     else:
+            #         # No other sequence groups can be preempted.
+            #         # Preempt the current sequence group.
+            #         self._preempt(seq_group)
+            #         preempted.append(seq_group)
+            #         break
+            # else:
+            #     # Append new slots to the sequence group.
+            #     # self._append_slot(seq_group, blocks_to_copy)
+            running.append(seq_group)
+        self.running = running
+
+        # TODO (txy): inplement below methods
+        # # Swap in the sequence groups in the SWAPPED state if possible.
+        # self.swapped = self.policy.sort_by_priority(now, self.swapped)
+        # if not preempted:
+        #     num_curr_seqs = sum(seq_group.get_max_num_running_seqs()
+        #                         for seq_group in self.running)
+
+        #     while self.swapped:
+        #         seq_group = self.swapped[0]
+        #         # If the sequence group cannot be swapped in, stop.
+        #         # if not self.block_manager.can_swap_in(seq_group):
+        #         #     break
+        #         if self.seq_ability <= 0:
+        #             break
+
+        #         # The total number of sequences in the RUNNING state should not
+        #         # exceed the maximum number of sequences.
+        #         num_new_seqs = seq_group.get_max_num_running_seqs()
+        #         if (num_curr_seqs + num_new_seqs >
+        #                 self.scheduler_config.max_num_seqs):
+        #             break
+
+        #         seq_group = self.swapped.pop(0)
+        #         # self._swap_in(seq_group, blocks_to_swap_in)
+        #         # self._append_slot(seq_group, blocks_to_copy)
+        #         num_curr_seqs += num_new_seqs
+        #         self.running.append(seq_group)
+
         # Each sequence in the generation phase only takes one token slot.
         # Therefore, the number of batched tokens is equal to the number of
         # sequences in the RUNNING state.
@@ -280,3 +350,85 @@ class FixedWindowScheduler:
             seq_group for seq_group in self.running
             if not seq_group.is_finished()
         ]
+
+    def _preempt(
+        self,
+        seq_group: SequenceGroup,
+        blocks_to_swap_out: Optional[Dict[int, int]]=None,
+        preemption_mode: Optional[PreemptionMode]=None,
+    ) -> None:
+        # If preemption mode is not specified, we determine the mode as follows:
+        # We use recomputation by default since it incurs lower overhead than
+        # swapping. However, when the sequence group has multiple sequences
+        # (e.g., beam search), recomputation is not currently supported. In
+        # such a case, we use swapping instead.
+        # FIXME(woosuk): This makes our scheduling policy a bit bizarre.
+        # As swapped sequences are prioritized over waiting sequences,
+        # sequence groups with multiple sequences are implicitly prioritized
+        # over sequence groups with a single sequence.
+        # TODO(woosuk): Support recomputation for sequence groups with multiple
+        # sequences. This may require a more sophisticated CUDA kernel.
+        if preemption_mode is None:
+            if seq_group.get_max_num_running_seqs() == 1:
+                preemption_mode = PreemptionMode.RECOMPUTE
+            else:
+                preemption_mode = PreemptionMode.SWAP
+        if preemption_mode == PreemptionMode.RECOMPUTE:
+            self._preempt_by_recompute(seq_group)
+        elif preemption_mode == PreemptionMode.SWAP:
+            self._preempt_by_swap(seq_group, blocks_to_swap_out)
+        else:
+            raise AssertionError("Invalid preemption mode.")  # noqa
+
+    def _preempt_by_recompute(
+        self,
+        seq_group: SequenceGroup,
+    ) -> None:
+        seqs = seq_group.get_seqs(status=SequenceStatus.RUNNING)
+        # len(seqs) should be 1
+        for seq in seqs:
+            seq.status = SequenceStatus.WAITING
+            # self.block_manager.free(seq)
+            if not self.kv_cache[0][0].get(seq.seq_id) is None:
+                for i in range(len(self.kv_cache)):
+                    for j in range(2):
+                        del self.kv_cache[i][j][seq.seq_id]
+
+        # NOTE: For FCFS, we insert the preempted sequence group to the front
+        # of the waiting queue.
+        self.waiting.insert(0, seq_group)
+
+    # TODO (txy): inplement below methods
+    def _preempt_by_swap(
+        self,
+        seq_group: SequenceGroup,
+        blocks_to_swap_out: Dict[int, int],
+    ) -> None:
+        self._swap_out(seq_group, blocks_to_swap_out)
+        self.swapped.append(seq_group)
+
+    def _swap_in(
+        self,
+        seq_group: SequenceGroup,
+        blocks_to_swap_in: Dict[int, int],
+    ) -> None:
+        mapping = self.block_manager.swap_in(seq_group)
+        blocks_to_swap_in.update(mapping)
+        for seq in seq_group.get_seqs(status=SequenceStatus.SWAPPED):
+            seq.status = SequenceStatus.RUNNING
+
+    def _swap_out(
+        self,
+        seq_group: SequenceGroup,
+        blocks_to_swap_out: Dict[int, int],
+    ) -> None:
+        if not self.block_manager.can_swap_out(seq_group):
+            # FIXME(woosuk): Abort the sequence group instead of aborting the
+            # entire engine.
+            raise RuntimeError(  # noqa
+                "Aborted due to the lack of CPU swap space. Please increase "
+                "the swap space to avoid this error.")
+        mapping = self.block_manager.swap_out(seq_group)
+        blocks_to_swap_out.update(mapping)
+        for seq in seq_group.get_seqs(status=SequenceStatus.RUNNING):
+            seq.status = SequenceStatus.SWAPPED

python/llm/src/bigdl/llm/vllm/model_executor/models/bigdl_llama.py

@@ -172,6 +172,7 @@ class BigDLLlamaForCausalLM(BigDLModelForCausalLM):
                 # "return_dict": True,
             }
         # pdb.set_trace()
+
         if self.device.type == 'xpu':
             torch.xpu.empty_cache()
         st_timestamp = time.perf_counter()

python/llm/src/bigdl/llm/vllm/model_executor/models/bigdl_model.py

@@ -21,6 +21,10 @@ from transformers import LlamaConfig
 
 from bigdl.llm.vllm.sequence import SequenceOutputs, SequenceGroupMetadata
 from bigdl.llm.transformers.models.utils import extend_kv_cache
+from bigdl.llm.vllm.logger import init_logger
+
+logger = init_logger(__name__)
+
 
 zero_cache_dict = {}