test_scheduler.py

# SPDX-License-Identifier: Apache-2.0

import time
from collections import deque
from unittest.mock import MagicMock

import pytest  # noqa
from torch import Use  # noqa

from vllm.config import CacheConfig, LoRAConfig, SchedulerConfig
from vllm.core.interfaces import AllocStatus
from vllm.core.scheduler import Scheduler, SchedulingBudget
from vllm.lora.request import LoRARequest
from vllm.sequence import SequenceGroup

from .utils import (append_new_token, append_new_token_seq,
                    append_new_token_seq_group, create_dummy_prompt,
                    get_sequence_groups, schedule_and_update_computed_tokens)


def test_scheduler_add_seq_group():
    block_size = 4
    scheduler_config = SchedulerConfig(
        "generate",
        max_num_batched_tokens=100,
        max_num_seqs=64,
        max_model_len=1,
    )
    cache_config = CacheConfig(block_size, 1.0, 1, cache_dtype="auto")
    cache_config.num_cpu_blocks = 4
    cache_config.num_gpu_blocks = 4
    scheduler = Scheduler(scheduler_config, cache_config, None)

    # Add seq group to scheduler.
    num_seq_group = 4
    for i in range(num_seq_group):
        _, seq_group = create_dummy_prompt(str(i),
                                           block_size,
                                           block_size=block_size)
        scheduler.add_seq_group(seq_group)
        assert scheduler.get_num_unfinished_seq_groups() == i + 1


def test_scheduler_abort_seq_group():
    block_size = 4
    scheduler_config = SchedulerConfig(
        "generate",
        max_num_batched_tokens=100,
        max_num_seqs=64,
        max_model_len=1,
    )
    cache_config = CacheConfig(block_size, 1.0, 1, "auto")
    cache_config.num_cpu_blocks = 4
    cache_config.num_gpu_blocks = 4
    scheduler = Scheduler(scheduler_config, cache_config, None)

    # Add multiple seq groups to scheduler.
    num_seq_group = 4
    request_ids: set[str] = set()
    for i in range(num_seq_group):
        _, seq_group = create_dummy_prompt(str(i), block_size)
        scheduler.add_seq_group(seq_group)
        request_ids.add(str(i))

    # Abort all added seq groups.
    assert scheduler.get_num_unfinished_seq_groups() == num_seq_group
    scheduler.abort_seq_group(request_ids)
    assert scheduler.get_num_unfinished_seq_groups() == 0


def test_scheduler_schedule_simple():
    block_size = 4
    num_seq_group = 4
    max_model_len = 16
    scheduler_config = SchedulerConfig(
        "generate",
        max_num_batched_tokens=64,
        max_num_seqs=num_seq_group,
        max_model_len=max_model_len,
    )
    cache_config = CacheConfig(block_size, 1.0, 1, "auto")
    cache_config.num_cpu_blocks = 8
    cache_config.num_gpu_blocks = 8
    scheduler = Scheduler(scheduler_config, cache_config, None)
    running: list[SequenceGroup] = []

    # Add seq groups to scheduler.
    for i in range(num_seq_group):
        _, seq_group = create_dummy_prompt(str(i),
                                           prompt_length=block_size,
                                           block_size=block_size)
        scheduler.add_seq_group(seq_group)
        running.append(seq_group)

    # Schedule seq groups prompts.
    num_tokens = block_size * num_seq_group
    seq_group_meta, out = schedule_and_update_computed_tokens(scheduler)
    assert set(get_sequence_groups(out)) == set(running)
    assert out.num_batched_tokens == num_tokens
    assert (not out.blocks_to_copy and not out.blocks_to_swap_in
            and not out.blocks_to_swap_out)
    assert len(seq_group_meta) == num_seq_group
    append_new_token(out, 1)

    # Schedule seq groups generation.
    seq_group_meta, out = schedule_and_update_computed_tokens(scheduler)
    assert set(get_sequence_groups(out)) == set(running)
    assert out.num_batched_tokens == num_seq_group
    assert (not out.blocks_to_copy and not out.blocks_to_swap_in
            and not out.blocks_to_swap_out)
    assert len(seq_group_meta) == num_seq_group
    append_new_token(out, 1)


def test_scheduler_prefill_prioritized():
    """Verify running batched tokens are not applied to prefill requests."""
    block_size = 4
    max_model_len = 30
    max_batched_num_tokens = 30
    scheduler_config = SchedulerConfig(
        "generate",
        max_num_batched_tokens=max_batched_num_tokens,
        max_num_seqs=2,
        max_model_len=max_model_len,
    )
    cache_config = CacheConfig(block_size, 1.0, 1, "auto")
    cache_config.num_cpu_blocks = 16
    cache_config.num_gpu_blocks = 16
    scheduler = Scheduler(scheduler_config, cache_config, None)

    # Add seq groups to scheduler.
    _, seq_group_a = create_dummy_prompt("1", 1, block_size=block_size)
    scheduler.add_seq_group(seq_group_a)

    # Schedule seq groups prompts.
    _, out = schedule_and_update_computed_tokens(scheduler)
    assert get_sequence_groups(out) == [seq_group_a]

    # Add a new prefill request B.
    _, seq_group_b = create_dummy_prompt("2", 30, block_size=block_size)
    scheduler.add_seq_group(seq_group_b)

    # Verify prefill requests are prioritized. Since max_batched_num_tokens
    # is 1, new prefill request has to be scheduled first.
    _, out = schedule_and_update_computed_tokens(scheduler)
    assert get_sequence_groups(out) == [seq_group_b]


def test_scheduler_schedule_preempt_abort():
    block_size = 4
    max_model_len = 16
    scheduler_config = SchedulerConfig(
        "generate",
        max_num_batched_tokens=64,
        max_num_seqs=2,
        max_model_len=max_model_len,
    )
    cache_config = CacheConfig(block_size, 1.0, 1, "auto")
    cache_config.num_cpu_blocks = 2
    cache_config.num_gpu_blocks = 2
    scheduler = Scheduler(scheduler_config, cache_config, None)

    # Add seq groups to scheduler.
    seq_a, seq_group_a = create_dummy_prompt("1",
                                             block_size,
                                             block_size=block_size)
    seq_b, seq_group_b = create_dummy_prompt("2",
                                             block_size,
                                             block_size=block_size)
    scheduler.add_seq_group(seq_group_a)
    scheduler.add_seq_group(seq_group_b)

    # Schedule seq groups prompts.
    seq_group_meta, out = schedule_and_update_computed_tokens(scheduler)
    assert get_sequence_groups(out) == [seq_group_a, seq_group_b]
    assert out.num_batched_tokens == block_size * 2  # seq_a and seq_b
    assert (not out.blocks_to_copy and not out.blocks_to_swap_in
            and not out.blocks_to_swap_out)
    assert len(seq_group_meta) == 2
    assert scheduler.get_num_unfinished_seq_groups() == 2

    # Append "generated" tokens, allowing the sequence to mark prompt tokens as
    # processed.
    append_new_token(out, 1)

    # Schedule seq groups generation and preempt seq group b.
    seq_group_meta, out = schedule_and_update_computed_tokens(scheduler)
    assert get_sequence_groups(out) == [seq_group_a]
    assert out.num_batched_tokens == 1
    assert (not out.blocks_to_copy and not out.blocks_to_swap_in
            and not out.blocks_to_swap_out)
    assert len(seq_group_meta) == 1
    assert scheduler.get_num_unfinished_seq_groups() == 2
    assert out.preempted == 1

    # Abort seq group a. Re-schedule seq group b prompt with recomputation.
    scheduler.abort_seq_group("1")
    seq_group_meta, out = schedule_and_update_computed_tokens(scheduler)
    assert get_sequence_groups(out) == [seq_group_b]
    assert out.num_batched_tokens == 5  # 4 prompt + 1 generation.
    assert (not out.blocks_to_copy and not out.blocks_to_swap_in
            and not out.blocks_to_swap_out)
    assert len(seq_group_meta) == 1
    assert scheduler.get_num_unfinished_seq_groups() == 1


def test_scheduler_max_seqs():
    block_size = 4
    num_seq_group = 4
    max_seq_group = 2
    max_model_len = 16
    scheduler_config = SchedulerConfig(
        "generate",
        max_num_batched_tokens=64,
        max_num_seqs=max_seq_group,
        max_model_len=max_model_len,
    )
    cache_config = CacheConfig(block_size, 1.0, 1, "auto")
    cache_config.num_cpu_blocks = 8
    cache_config.num_gpu_blocks = 8
    scheduler = Scheduler(scheduler_config, cache_config, None)

    all_seq_groups: list[SequenceGroup] = []
    # Add seq groups to scheduler.
    for i in range(num_seq_group):
        _, seq_group = create_dummy_prompt(str(i),
                                           prompt_length=block_size,
                                           block_size=block_size)
        all_seq_groups.append(seq_group)

    # Append 1 seq group
    scheduler.add_seq_group(all_seq_groups[0])

    # Schedule seq groups prompts.
    seq_group_meta, out = schedule_and_update_computed_tokens(scheduler)
    assert set(get_sequence_groups(out)) == set([all_seq_groups[0]])
    append_new_token(out, 1)

    # Schedule seq groups generation.
    seq_group_meta, out = schedule_and_update_computed_tokens(scheduler)
    assert set(get_sequence_groups(out)) == set([all_seq_groups[0]])
    append_new_token(out, 1)

    # Append 2 more seq group
    scheduler.add_seq_group(all_seq_groups[1])
    scheduler.add_seq_group(all_seq_groups[2])

    # Schedule seq groups prompts.
    # Only 1 seq group should be scheduled since max_seq_group is 2
    # and one is prompting.
    _, out = schedule_and_update_computed_tokens(scheduler)
    assert set(get_sequence_groups(out)) == set([all_seq_groups[1]])


def test_scheduler_delay_factor():
    block_size = 4
    scheduler_config = SchedulerConfig(
        "generate",
        max_num_batched_tokens=100,
        max_num_seqs=64,
        max_model_len=16,
        delay_factor=0.5,
    )
    cache_config = CacheConfig(block_size, 1.0, 1, "auto")
    cache_config.num_cpu_blocks = 8
    cache_config.num_gpu_blocks = 8
    scheduler = Scheduler(scheduler_config, cache_config, None)

    # schedule first prompt
    seq_group_meta, seq_group = create_dummy_prompt("0",
                                                    prompt_length=block_size,
                                                    block_size=block_size)
    scheduler.add_seq_group(seq_group)
    seq_group_meta, out = schedule_and_update_computed_tokens(scheduler)
    assert out.num_prefill_groups > 0
    assert seq_group_meta[0].request_id == '0'
    append_new_token(out, 1)

    # wait for a second before scheduling next prompt
    time.sleep(1)
    seq_group_meta, seq_group = create_dummy_prompt("1",
                                                    prompt_length=block_size,
                                                    block_size=block_size)
    scheduler.add_seq_group(seq_group)

    # second prompt should *not* be scheduled
    seq_group_meta, out = schedule_and_update_computed_tokens(scheduler)
    assert out.num_prefill_groups == 0
    assert seq_group_meta[0].request_id == '0'
    append_new_token(out, 1)

    # wait for more than 0.5 second and try again
    time.sleep(0.6)
    seq_group_meta, out = schedule_and_update_computed_tokens(scheduler)
    assert out.num_prefill_groups > 0
    assert seq_group_meta[0].request_id == '1'
    append_new_token(out, 1)


def initialize_scheduler(
    *,
    max_num_seqs=1000,
    max_token_budget=1000,
    max_model_len=1000,
    lora_config=None,
    block_size=4,
    num_cpu_blocks=8,
    num_gpu_blocks=8,
    enable_prefix_caching=False,
    enable_chunked_prefill=False,
):
    block_size = block_size
    scheduler_config = SchedulerConfig(
        "generate",
        max_num_batched_tokens=max_token_budget,
        max_num_seqs=max_num_seqs,
        max_model_len=max_model_len,
        enable_chunked_prefill=enable_chunked_prefill,
    )
    cache_config = CacheConfig(
        block_size,
        1.0,
        1,
        "auto",
        enable_prefix_caching=enable_prefix_caching,
    )
    cache_config.num_cpu_blocks = num_cpu_blocks
    cache_config.num_gpu_blocks = num_gpu_blocks
    scheduler = Scheduler(scheduler_config, cache_config, lora_config)
    return scheduler


def create_token_budget(token_budget: int = 10000,
                        max_num_seqs: int = 10000) -> SchedulingBudget:
    return SchedulingBudget(
        token_budget=token_budget,
        max_num_seqs=max_num_seqs,
    )


def add_token_budget(budget: SchedulingBudget,
                     num_batched_tokens: int = 0,
                     num_curr_seqs: int = 0):
    mock_seq_group = create_dummy_prompt('10', prompt_length=60)[1]
    budget.add_num_batched_tokens(mock_seq_group.request_id,
                                  num_batched_tokens)
    budget.add_num_seqs(mock_seq_group.request_id, num_curr_seqs)


def test_prefill_schedule_max_prompt_len():
    """
    Test prompt longer than max_prompt_len is aborted.
    """
    block_size = 4
    scheduler = initialize_scheduler(max_model_len=30, block_size=block_size)
    _, seq_group = create_dummy_prompt("0",
                                       prompt_length=60,
                                       block_size=block_size)
    scheduler.add_seq_group(seq_group)
    budget = create_token_budget()
    output = scheduler._schedule_prefills(budget, None)
    remaining_waiting = scheduler.waiting
    assert len(output.ignored_seq_groups) == 1
    assert len(output.seq_groups) == 0
    assert budget.num_batched_tokens == 0
    assert budget.num_curr_seqs == 0
    assert len(remaining_waiting) == 0


def test_prefill_schedule_token_budget():
    """
    Test token budget respected.
    """
    block_size = 4
    scheduler = initialize_scheduler(block_size=block_size,
                                     num_cpu_blocks=64,
                                     num_gpu_blocks=64)
    budget = create_token_budget(token_budget=0)
    for i in range(2):
        _, seq_group = create_dummy_prompt(str(i),
                                           prompt_length=60,
                                           block_size=block_size)
        scheduler.add_seq_group(seq_group)

    # 0 token budget == nothing is scheduled.
    output = scheduler._schedule_prefills(budget, None)
    remaining_waiting = scheduler.waiting
    assert len(output.ignored_seq_groups) == 0
    assert len(output.seq_groups) == 0
    assert budget.num_batched_tokens == 0
    assert budget.num_curr_seqs == 0
    assert len(remaining_waiting) == 2

    # 60 token budget == 1 request scheduled.
    budget = create_token_budget(token_budget=60)
    output = scheduler._schedule_prefills(budget, None)
    remaining_waiting = scheduler.waiting
    assert len(output.ignored_seq_groups) == 0
    assert len(output.seq_groups) == 1
    assert budget.num_batched_tokens == 60
    assert budget.num_curr_seqs == 1
    assert len(remaining_waiting) == 1

    # Test when current_batched_tokens respected.
    scheduler = initialize_scheduler(block_size=block_size,
                                     num_cpu_blocks=16,
                                     num_gpu_blocks=16)
    budget = create_token_budget(token_budget=60)
    add_token_budget(budget, 30, 0)
    _, seq_group = create_dummy_prompt(str(i),
                                       prompt_length=60,
                                       block_size=block_size)
    # Cannot schedule a prompt that doesn't fit the budget.
    scheduler.add_seq_group(seq_group)
    output = scheduler._schedule_prefills(budget, None)
    remaining_waiting = scheduler.waiting
    assert len(output.ignored_seq_groups) == 0
    assert len(output.seq_groups) == 0
    assert budget.num_batched_tokens == 30
    assert budget.num_curr_seqs == 0
    assert len(remaining_waiting) == 1
    budget = create_token_budget(token_budget=90)
    add_token_budget(budget, 30, 0)
    output = scheduler._schedule_prefills(budget, None)
    remaining_waiting = scheduler.waiting
    assert len(output.seq_groups) == 1
    assert budget.num_batched_tokens == 90
    assert budget.num_curr_seqs == 1
    assert len(remaining_waiting) == 0


def test_prefill_schedule_max_seqs():
    """
    Test max seq respected.
    """
    block_size = 4
    scheduler = initialize_scheduler(block_size=block_size,
                                     num_cpu_blocks=64,
                                     num_gpu_blocks=64)
    budget = create_token_budget(max_num_seqs=2)
    for i in range(3):
        _, seq_group = create_dummy_prompt(str(i),
                                           prompt_length=60,
                                           block_size=block_size)
        scheduler.add_seq_group(seq_group)
    output = scheduler._schedule_prefills(budget, None)
    remaining_waiting = scheduler.waiting
    assert len(output.ignored_seq_groups) == 0
    assert len(output.seq_groups) == 2
    assert budget.num_batched_tokens == 120
    assert budget.num_curr_seqs == 2
    assert len(remaining_waiting) == 1

    # Verify curr_num_seqs respected.
    scheduler.waiting = deque()
    budget = create_token_budget(max_num_seqs=2)
    add_token_budget(budget, 0, 2)
    _, seq_group = create_dummy_prompt(str(i),
                                       prompt_length=60,
                                       block_size=block_size)
    scheduler.add_seq_group(seq_group)
    output = scheduler._schedule_prefills(budget, None)
    remaining_waiting = scheduler.waiting
    assert len(output.ignored_seq_groups) == 0
    assert len(output.seq_groups) == 0
    assert budget.num_batched_tokens == 0
    assert budget.num_curr_seqs == 2
    assert len(remaining_waiting) == 1


def test_prefill_schedule_max_lora():
    """
    Test max lora is respected and prioritized.
    """
    block_size = 4
    lora_config = LoRAConfig(max_lora_rank=8, max_loras=1)
    scheduler = initialize_scheduler(lora_config=lora_config,
                                     block_size=block_size,
                                     num_cpu_blocks=64,
                                     num_gpu_blocks=64)
    budget = create_token_budget(token_budget=120)
    curr_loras: set[int] = set()
    for i in range(2):
        _, seq_group = create_dummy_prompt(str(i),
                                           prompt_length=60,
                                           block_size=block_size,
                                           lora_request=LoRARequest(
                                               lora_name=str(i),
                                               lora_int_id=i + 1,
                                               lora_path="abc"))
        scheduler.add_seq_group(seq_group)
    # Add two more requests to verify lora is prioritized.
    # 0: LoRA, 1: LoRA, 2: regular, 3: regular
    # In the first iteration, index 0, 2 is scheduled.
    # If a request is not scheduled because it hits max lora, it is
    # prioritized. Verify that.
    for i in range(2, 4):
        _, seq_group = create_dummy_prompt(str(i),
                                           prompt_length=60,
                                           block_size=block_size)
        scheduler.add_seq_group(seq_group)
    # Schedule 2 requests (0 and 2)
    output = scheduler._schedule_prefills(budget, curr_loras)
    remaining_waiting = scheduler.waiting
    assert len(output.ignored_seq_groups) == 0
    assert len(output.seq_groups) == 2
    assert budget.num_batched_tokens == 120
    assert budget.num_curr_seqs == 2
    assert len(remaining_waiting) == 2
    assert len(curr_loras) == 1
    # The second lora request is scheduled next as FCFS policy.
    # Reset curr_loras so that it can be scheduled.
    curr_loras = set()
    budget = create_token_budget(token_budget=60)
    output = scheduler._schedule_prefills(budget, curr_loras)
    remaining_waiting = scheduler.waiting
    assert len(output.seq_groups) == 1
    assert output.seq_groups[0].seq_group.request_id == "1"
    assert len(remaining_waiting) == 1
    assert len(curr_loras) == 1
    assert budget.num_batched_tokens == 60


def test_prefill_schedule_no_block_manager_capacity():
    """
    Test sequence cannot be scheduled due to block manager has no capacity.
    """
    block_size = 4
    scheduler = initialize_scheduler(block_size=block_size,
                                     num_gpu_blocks=128,
                                     num_cpu_blocks=128)
    budget = create_token_budget()
    for i in range(3):
        _, seq_group = create_dummy_prompt(str(i),
                                           prompt_length=60,
                                           block_size=block_size)
        scheduler.add_seq_group(seq_group)
    scheduler.block_manager.can_allocate = MagicMock()
    scheduler.block_manager.can_allocate.return_value = AllocStatus.LATER
    output = scheduler._schedule_prefills(budget, None)
    remaining_waiting = scheduler.waiting
    assert len(output.ignored_seq_groups) == 0
    assert len(output.seq_groups) == 0
    assert budget.num_batched_tokens == 0
    assert budget.num_curr_seqs == 0
    assert len(remaining_waiting) == 3

    scheduler = initialize_scheduler()
    budget = create_token_budget()
    for i in range(3):
        _, seq_group = create_dummy_prompt(str(i),
                                           prompt_length=60,
                                           block_size=block_size)
        scheduler.add_seq_group(seq_group)
    scheduler.block_manager.can_allocate = MagicMock()
    scheduler.block_manager.can_allocate.return_value = AllocStatus.NEVER
    output = scheduler._schedule_prefills(budget, None)
    remaining_waiting = scheduler.waiting
    assert len(output.ignored_seq_groups) == 3
    assert len(output.seq_groups) == 0
    assert budget.num_batched_tokens == 0
    assert budget.num_curr_seqs == 0
    assert len(remaining_waiting) == 0


def test_decode_schedule_preempted():
    """
    Test decodes cannot be scheduled and preempted.
    """
    block_size = 4
    scheduler = initialize_scheduler(block_size=block_size,
                                     num_cpu_blocks=64,
                                     num_gpu_blocks=64)
    curr_loras = None
    for i in range(3):
        _, seq_group = create_dummy_prompt(str(i),
                                           prompt_length=60,
                                           block_size=block_size)
        scheduler._allocate_and_set_running(seq_group)
        append_new_token_seq_group(60, seq_group, 1)
        scheduler._add_seq_group_to_running(seq_group)
    scheduler.block_manager.can_append_slots = MagicMock()

    def cannot_append_second_group(seq_group, num_lookahead_slots):
        return seq_group.request_id != "1"

    scheduler.block_manager.can_append_slots.side_effect = (
        cannot_append_second_group)

    # 1 cannot be scheduled, and the lowest priority (request 2)
    # should be preempted. 1 will also be preempted.
    budget = create_token_budget()
    output = scheduler._schedule_running(budget, curr_loras)
    remainig_running = scheduler.running
    assert len(remainig_running) == 0
    assert len(output.decode_seq_groups) == 1
    assert len(output.prefill_seq_groups) == 0
    assert output.decode_seq_groups[0].seq_group.request_id == "0"
    assert len(output.preempted) == 2
    # Verify budgets are updated.
    assert budget.num_batched_tokens == 1
    # NOTE: When enable_chunk is False, num_seqs budget is not updated.
    # assert budget.num_curr_seqs == 1
    # Both should be preempted, not swapped.
    assert output.blocks_to_swap_out == []
    # Nothing is copied.
    assert output.blocks_to_copy == []


def test_schedule_decode_blocks_to_copy_update():
    """
    Verify blocks_to_copy is updated.
    """
    block_size = 4
    scheduler = initialize_scheduler(block_size=4,
                                     num_cpu_blocks=16,
                                     num_gpu_blocks=16)
    _, seq_group = create_dummy_prompt("1",
                                       prompt_length=60,
                                       block_size=block_size)
    curr_loras = None
    scheduler._allocate_and_set_running(seq_group)
    append_new_token_seq_group(60, seq_group, 1)
    scheduler._add_seq_group_to_running(seq_group)

    # The last request should be swapped out.
    scheduler.block_manager.append_slots = MagicMock()
    scheduler.block_manager.append_slots.return_value = [(2, 3)]

    budget = create_token_budget()
    output = scheduler._schedule_running(budget, curr_loras)
    remaining_running = scheduler.running
    assert len(remaining_running) == 0
    assert len(output.decode_seq_groups) == 1
    assert len(output.prefill_seq_groups) == 0
    assert len(output.preempted) == 0
    assert len(output.swapped_out) == 0
    # Nothing is preempted.
    assert output.blocks_to_swap_out == []
    # Since append_slot returns the source -> dist mapping, it should
    # applied.
    assert output.blocks_to_copy == [(2, 3)]


def test_schedule_swapped_max_loras():
    block_size = 4
    lora_config = LoRAConfig(max_lora_rank=8, max_loras=1)
    scheduler = initialize_scheduler(lora_config=lora_config,
                                     block_size=block_size,
                                     num_cpu_blocks=32,
                                     num_gpu_blocks=32)
    curr_loras: set[int] = set()
    blocks_to_swap_out: list[tuple[int, int]] = []
    for i in range(2):
        _, seq_group = create_dummy_prompt(str(i),
                                           prompt_length=60,
                                           block_size=block_size,
                                           lora_request=LoRARequest(
                                               lora_name=str(i),
                                               lora_int_id=i + 1,
                                               lora_path="abc"))
        scheduler._allocate_and_set_running(seq_group)
        append_new_token_seq_group(60, seq_group, 1)
        scheduler._swap_out(seq_group, blocks_to_swap_out)
        scheduler._add_seq_group_to_swapped(seq_group)

    budget = create_token_budget()
    output = scheduler._schedule_swapped(budget, curr_loras)
    remaining_swapped = scheduler.swapped
    assert len(remaining_swapped) == 1
    assert budget.num_batched_tokens == 1
    assert budget.num_curr_seqs == 1
    assert len(output.decode_seq_groups) == 1
    assert len(output.prefill_seq_groups) == 0
    assert len(curr_loras) == 1


def test_schedule_swapped_cannot_swap_in():
    block_size = 4
    scheduler = initialize_scheduler(block_size=block_size,
                                     num_cpu_blocks=32,
                                     num_gpu_blocks=32)
    curr_loras = None
    blocks_to_swap_out: list[tuple[int, int]] = []
    for i in range(2):
        _, seq_group = create_dummy_prompt(str(i),
                                           prompt_length=60,
                                           block_size=block_size)
        scheduler._allocate_and_set_running(seq_group)
        append_new_token_seq_group(60, seq_group, 1)
        scheduler._swap_out(seq_group, blocks_to_swap_out)
        scheduler._add_seq_group_to_swapped(seq_group)

    # The last request should be swapped out.
    scheduler.block_manager.can_swap_in = MagicMock()
    scheduler.block_manager.can_swap_in.return_value = AllocStatus.LATER
    # Since we cannot swap in, none of the requests are swapped in.
    budget = create_token_budget()
    output = scheduler._schedule_swapped(budget, curr_loras)
    remaining_swapped = scheduler.swapped
    assert len(remaining_swapped) == 2
    assert budget.num_batched_tokens == 0
    assert budget.num_curr_seqs == 0
    assert len(output.decode_seq_groups) == 0
    assert len(output.prefill_seq_groups) == 0


def test_infeasible_swap():
    block_size = 4
    scheduler = initialize_scheduler(block_size=block_size,
                                     num_cpu_blocks=32,
                                     num_gpu_blocks=32)
    curr_loras = None
    blocks_to_swap_out: list[tuple[int, int]] = []
    for i in range(2):
        _, seq_group = create_dummy_prompt(str(i),
                                           prompt_length=60,
                                           block_size=block_size)
        scheduler._allocate_and_set_running(seq_group)
        append_new_token_seq_group(60, seq_group, 1)
        scheduler._swap_out(seq_group, blocks_to_swap_out)
        scheduler._add_seq_group_to_swapped(seq_group)

    # The last request should be swapped out.
    scheduler.block_manager.can_swap_in = MagicMock()
    scheduler.block_manager.can_swap_in.return_value = AllocStatus.NEVER
    # Since we cannot swap in, none of the requests are swapped in.
    budget = create_token_budget()
    output = scheduler._schedule_swapped(budget, curr_loras)
    remaining_swapped = scheduler.swapped
    assert len(remaining_swapped) == 0
    assert len(output.infeasible_seq_groups) == 2
    assert budget.num_batched_tokens == 0
    assert budget.num_curr_seqs == 0
    assert len(output.decode_seq_groups) == 0
    assert len(output.prefill_seq_groups) == 0


def test_schedule_swapped_blocks_to_copy():
    block_size = 4
    scheduler = initialize_scheduler(block_size=block_size,
                                     num_cpu_blocks=32,
                                     num_gpu_blocks=32)
    curr_loras = None
    _, seq_group = create_dummy_prompt("1",
                                       prompt_length=60,
                                       block_size=block_size)
    scheduler._allocate_and_set_running(seq_group)
    append_new_token_seq_group(60, seq_group, 1)
    blocks_to_swap_out: list[tuple[int, int]] = []
    scheduler._swap_out(seq_group, blocks_to_swap_out)
    scheduler._add_seq_group_to_swapped(seq_group)

    # The last request should be swapped out.
    scheduler.block_manager.append_slots = MagicMock()
    scheduler.block_manager.append_slots.return_value = [(2, 3)]

    budget = create_token_budget()
    output = scheduler._schedule_swapped(budget, curr_loras)
    remaining_swapped = scheduler.swapped
    assert len(remaining_swapped) == 0
    assert len(output.decode_seq_groups) == 1
    assert len(output.prefill_seq_groups) == 0
    assert output.blocks_to_copy == [(2, 3)]


def test_scheduling_budget():
    TOKEN_BUDGET = 4
    MAX_SEQS = 4
    budget = SchedulingBudget(token_budget=TOKEN_BUDGET, max_num_seqs=MAX_SEQS)
    assert budget.can_schedule(num_new_tokens=1, num_new_seqs=1)
    assert budget.can_schedule(num_new_tokens=4, num_new_seqs=4)
    assert not budget.can_schedule(num_new_tokens=1, num_new_seqs=5)
    assert not budget.can_schedule(num_new_tokens=5, num_new_seqs=1)
    assert not budget.can_schedule(num_new_tokens=5, num_new_seqs=5)
    assert budget.remaining_token_budget() == TOKEN_BUDGET

    # Verify add/subtract num batched tokens.
    _, seq_group = create_dummy_prompt("1", 3)
    budget.add_num_batched_tokens(seq_group.request_id, 2)
    assert budget.remaining_token_budget() == 2
    assert budget.num_batched_tokens == 2
    assert budget.can_schedule(num_new_tokens=2, num_new_seqs=1)
    assert not budget.can_schedule(num_new_tokens=3, num_new_seqs=1)
    # Verify adding another seq group is no-op.
    budget.add_num_batched_tokens(seq_group.request_id, 2)
    assert budget.remaining_token_budget() == 2
    assert budget.num_batched_tokens == 2
    budget.subtract_num_batched_tokens(seq_group.request_id, 2)
    assert budget.remaining_token_budget() == 4
    assert budget.num_batched_tokens == 0
    budget.subtract_num_batched_tokens(seq_group.request_id, 2)
    assert budget.remaining_token_budget() == 4
    assert budget.num_batched_tokens == 0

    # Verify add/subtract max seqs.
    _, seq_group = create_dummy_prompt("1", 3)
    budget.add_num_seqs(seq_group.request_id, 2)
    assert budget.can_schedule(num_new_tokens=1, num_new_seqs=2)
    assert not budget.can_schedule(num_new_tokens=1, num_new_seqs=3)
    assert budget.num_curr_seqs == 2
    # Verify adding another seq group is no-op.
    budget.add_num_seqs(seq_group.request_id, 2)
    assert budget.num_curr_seqs == 2
    budget.subtract_num_seqs(seq_group.request_id, 2)
    assert budget.num_curr_seqs == 0
    budget.subtract_num_seqs(seq_group.request_id, 2)
    assert budget.num_curr_seqs == 0


@pytest.mark.parametrize("enable_prefix_caching", [True, False])
def test_prefix_caching_aware_prefills(enable_prefix_caching):
    """
    Test the below scenario:

    For 3 sequences, seqA, seqB, seqC, share the first block as prefix.

    The test verifies the below scenarios:
    1.  SeqA is first scheduled.
    2.  SeqB and SeqC can be prefilled together in a single schedule round
    even though there are not enough token budgets to prefill both without
    considering prefix caching.
    """

    block_size = 4
    max_num_batched_tokens = 12
    max_seq_group = 3
    scheduler = initialize_scheduler(
        block_size=block_size,
        num_cpu_blocks=16,
        num_gpu_blocks=16,
        max_token_budget=max_num_batched_tokens,
        max_num_seqs=max_seq_group,
        max_model_len=max_num_batched_tokens,
        enable_prefix_caching=enable_prefix_caching,
    )

    seqA_tokens = list(range(8))
    num_shared_tokens = 4
    seqB_tokens = seqA_tokens[:num_shared_tokens] + list(range(
        12, 16))  # Shared prefix first 4.
    seqC_tokens = seqA_tokens[:num_shared_tokens] + list(range(
        16, 20))  # Shared prefix first 4.

    seqA, seqA_group = create_dummy_prompt("0",
                                           prompt_tokens=seqA_tokens,
                                           block_size=block_size)
    seqB, seqB_group = create_dummy_prompt("1",
                                           prompt_tokens=seqB_tokens,
                                           block_size=block_size)
    seqC, seqC_group = create_dummy_prompt("2",
                                           prompt_tokens=seqC_tokens,
                                           block_size=block_size)

    # Schedule seqA prefill.
    scheduler.add_seq_group(seqA_group)
    metas, out, _ = scheduler.schedule()
    assert (len(out.scheduled_seq_groups) == 1
            and out.scheduled_seq_groups[0].seq_group == seqA_group)
    assert out.scheduled_seq_groups[0].token_chunk_size == len(seqA_tokens)

    # Schedule seqA decode.
    append_new_token_seq_group(len(seqA_tokens), seqA_group, 999)
    metas, out, _ = scheduler.schedule()

    assert len(out.scheduled_seq_groups) == 1
    assert out.scheduled_seq_groups[0].seq_group == seqA_group
    assert out.scheduled_seq_groups[0].token_chunk_size == 1

    # Schedule seqB and seqC prefills should work with prefix caching.
    scheduler.add_seq_group(seqB_group)
    scheduler.add_seq_group(seqC_group)
    metas, out, _ = scheduler.schedule()

    if enable_prefix_caching:
        assert len(out.scheduled_seq_groups) == 2
        assert set([
            out.scheduled_seq_groups[0].seq_group,
            out.scheduled_seq_groups[1].seq_group,
        ]) == set([seqB_group, seqC_group])
        assert len(metas) == 2
        for meta in metas:
            assert meta.token_chunk_size == 8
            assert (len(meta.computed_block_nums) == num_shared_tokens //
                    block_size)  # 1 Block for the 8 tokens.
    else:
        assert len(out.scheduled_seq_groups) == 1
        assert len(metas) == 1
        assert metas[0].token_chunk_size == 8
        assert len(metas[0].computed_block_nums) == 0  # No blocks computed.


def test_no_multiple_partial_prefills_with_chunked_prefill_and_prefix_caching(
):
    """
    This test verifies that we don't schedule new prefills if there's already
    a continuous prefill in progress even though the new prefills with shared
    prefix can fit in the token budget:

    - SeqA is being chunked prefill.
    - SeqB with the same prompt shouldn't be scheduled for prefill even though
    there's enough token budget to prefill the cached tokens.
    - Neither should seqC be scheduled.

    - When seqA is in decoding phase, seqB and seqC can be scheduled.
        - Entire seqB should be prefilled since it's a full prefix cache hit.
        - SeqC would be partially prefilled with the prefix shared, and the
        remaining unique tokens would be prefilled (rounded down to be
        block-size aligned).
    """

    block_size = 2
    max_num_batched_tokens = 4
    max_seq_group = 3
    scheduler = initialize_scheduler(
        block_size=block_size,
        num_cpu_blocks=16,
        num_gpu_blocks=16,
        max_token_budget=max_num_batched_tokens,
        max_num_seqs=max_seq_group,
        max_model_len=100,
        enable_prefix_caching=True,
        enable_chunked_prefill=True,
    )

    seqA_tokens = list(range(8))
    seqB_tokens = seqA_tokens
    seqC_shared_prefix_len = 4
    seqC_tokens = seqA_tokens[:seqC_shared_prefix_len] + list(range(12, 20))

    seqA, seqA_group = create_dummy_prompt("0",
                                           prompt_tokens=seqA_tokens,
                                           block_size=block_size)
    seqB, seqB_group = create_dummy_prompt("1",
                                           prompt_tokens=seqB_tokens,
                                           block_size=block_size)

    # Chunked prefill seqA.
    scheduler.add_seq_group(seqA_group)
    metas, out = schedule_and_update_computed_tokens(scheduler)
    assert len(out.scheduled_seq_groups) == 1
    assert out.scheduled_seq_groups[0].seq_group == seqA_group
    assert out.scheduled_seq_groups[0].token_chunk_size == 4

    # seqB should not be scheduled with ongoing prefills.
    scheduler.add_seq_group(seqB_group)
    metas, out = schedule_and_update_computed_tokens(scheduler)
    assert len(out.scheduled_seq_groups) == 1
    assert out.scheduled_seq_groups[0].seq_group == seqA_group
    assert out.scheduled_seq_groups[0].token_chunk_size == 4

    # both seqB and seqC can now be scheduled with seqA is over.
    # seqA is in decoding phase.
    append_new_token_seq(seqA, 999)
    seqC, seqC_group = create_dummy_prompt("2",
                                           prompt_tokens=seqC_tokens,
                                           block_size=block_size)
    scheduler.add_seq_group(seqC_group)
    metas, out = schedule_and_update_computed_tokens(scheduler)
    assert len(out.scheduled_seq_groups) == 3

    metas = {meta.request_id: meta for meta in metas}
    assert metas[seqA_group.request_id].token_chunk_size == 1  # Decode
    assert (metas[seqB_group.request_id].token_chunk_size == 8
            )  # Fully cached prefill
    assert (
        metas[seqC_group.request_id].token_chunk_size == 6
    ), "A partial prefix of C (4 tokens) should be prefilled, with the "
    "remaining tokens fit into 3 token budget (4-1 from the seqA). It will "
    "then be rounded down to 2 tokens on block size, thus 6 tokens in total."