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vLLM/tests/v1/worker/test_kv_block_zeroer.py
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# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
import pytest
import torch
from vllm.v1.worker.utils import KVBlockZeroer, _zero_kv_blocks_kernel
@pytest.mark.skipif(not torch.cuda.is_available(), reason="CUDA required")
def test_block_ids_are_not_overwritten_while_copy_is_in_flight():
device = torch.device("cuda")
num_blocks = 4
page_size_el = 4
storage = torch.ones((num_blocks, page_size_el), dtype=torch.int32, device=device)
# Build the minimal zeroer state directly so the test can focus on the
# in-flight copy behavior without constructing model attention groups.
zeroer = KVBlockZeroer.__new__(KVBlockZeroer)
zeroer.device = device
zeroer._meta = (
torch.tensor([storage.data_ptr()], dtype=torch.uint64, device=device),
torch.tensor([page_size_el], dtype=torch.int64, device=device),
page_size_el // page_size_el, # max_chunks = 1
page_size_el, # blk_size
1, # n_segs
)
stream = torch.cuda.Stream()
with torch.cuda.stream(stream):
# Keep the first nonblocking H2D copy pending while the host submits the
# second call. Each call must stage from its own pinned source so the
# first copy is not corrupted before it runs.
torch.cuda._sleep(10_000_000)
zeroer.zero_block_ids([1])
zeroer.zero_block_ids([2])
stream.synchronize()
assert torch.all(storage[0] == 1)
assert torch.all(storage[1] == 0)
assert torch.all(storage[2] == 0)
assert torch.all(storage[3] == 1)
@pytest.mark.skipif(not torch.cuda.is_available(), reason="CUDA required")
def test_non_uniform_page_sizes():
"""Two segments with different page sizes (e.g. MLA + DSA indexer)."""
device = torch.device("cuda")
num_blocks = 4
page_size_a = 10496 # int32 elements
page_size_b = 2112
storage_a = torch.ones((num_blocks, page_size_a), dtype=torch.int32, device=device)
storage_b = torch.ones((num_blocks, page_size_b), dtype=torch.int32, device=device)
zeroer = KVBlockZeroer.__new__(KVBlockZeroer)
zeroer.device = device
seg_page_sizes = [page_size_a, page_size_b]
max_ps = max(seg_page_sizes)
def largest_power_of_2_divisor(n):
return n & -n
blk_size = min(min(largest_power_of_2_divisor(ps) for ps in seg_page_sizes), 1024)
zeroer._meta = (
torch.tensor(
[storage_a.data_ptr(), storage_b.data_ptr()],
dtype=torch.uint64,
device=device,
),
torch.tensor(seg_page_sizes, dtype=torch.int64, device=device),
max_ps // blk_size,
blk_size,
2,
)
stream = torch.cuda.Stream()
with torch.cuda.stream(stream):
zeroer.zero_block_ids([1, 2])
stream.synchronize()
for storage in (storage_a, storage_b):
assert torch.all(storage[0] == 1)
assert torch.all(storage[1] == 0)
assert torch.all(storage[2] == 0)
assert torch.all(storage[3] == 1)
@pytest.mark.skipif(not torch.cuda.is_available(), reason="CUDA required")
def test_warmup_compiles_every_n_blocks_specialization():
"""After warmup, no launch should trigger a first-request JIT compile.
``n_blocks`` is ``do_not_specialize``, so a single warmup launch must
cover every block count.
"""
device = torch.device("cuda")
num_blocks = 64
page_size_el = 4
storage = torch.ones((num_blocks, page_size_el), dtype=torch.int32, device=device)
zeroer = KVBlockZeroer.__new__(KVBlockZeroer)
zeroer.device = device
zeroer._meta = (
torch.tensor([storage.data_ptr()], dtype=torch.uint64, device=device),
torch.tensor([page_size_el], dtype=torch.int64, device=device),
1, # max_chunks
page_size_el, # blk_size
1, # n_segs
)
def compiled_variants() -> set:
return {
key
for caches in _zero_kv_blocks_kernel.device_caches.values()
for key in caches[0]
}
zeroer.warmup(num_blocks)
torch.accelerator.synchronize()
warmed = compiled_variants()
assert warmed
for n_blocks in (1, 2, 3, 16, 32):
zeroer.zero_block_ids(list(range(n_blocks)))
torch.accelerator.synchronize()
assert compiled_variants() == warmed
@pytest.mark.skipif(not torch.cuda.is_available(), reason="CUDA required")
def test_warmup_respects_available_block_count():
"""An empty KV cache must not be warmed with out-of-range block IDs."""
device = torch.device("cuda")
page_size_el = 4
storage = torch.ones((1, page_size_el), dtype=torch.int32, device=device)
zeroer = KVBlockZeroer.__new__(KVBlockZeroer)
zeroer.device = device
zeroer._meta = (
torch.tensor([storage.data_ptr()], dtype=torch.uint64, device=device),
torch.tensor([page_size_el], dtype=torch.int64, device=device),
1,
page_size_el,
1,
)
zeroer.warmup(0)
torch.accelerator.synchronize()
assert torch.all(storage == 1)