perf: accelerate decode linear with bf16 gemv

- add decode-shape benchmark harness
- add bf16 GEMV CUDA primitive with head-dim generic kernel
- dispatch decode-time linear layers to gemv for M=1
- extend gemv coverage to small decode batches
This commit is contained in:
0z5a
2026-09-02 13:11:25 +08:00
parent 9c3ef0c2a1
commit a144d7f306
14 changed files with 1242 additions and 3 deletions
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import pytest
import torch
import torch.nn.functional as F
from astrai.extension import bf16_gemv, is_available
GEMV_AVAILABLE = (
torch.cuda.is_available()
and is_available("bf16_gemv")
and torch.cuda.get_device_capability() >= (8, 0)
)
skip_no_gemv = pytest.mark.skipif(
not GEMV_AVAILABLE,
reason="BF16 GEMV requires a built kernel and compute capability 8.0+",
)
@skip_no_gemv
@pytest.mark.parametrize(
"n,k",
[(256, 1536), (1536, 1536), (6912, 1536), (1536, 6912), (100000, 1536)],
)
def test_bf16_gemv_matches_linear_shape_families(n, k):
torch.manual_seed(17)
x = torch.randn(k, device="cuda", dtype=torch.bfloat16)
weight = torch.randn(n, k, device="cuda", dtype=torch.bfloat16)
actual = bf16_gemv(x, weight)
expected = F.linear(x, weight)
assert actual.shape == (n,)
torch.testing.assert_close(actual, expected, rtol=0.02, atol=0.25)
@skip_no_gemv
@pytest.mark.parametrize("m", [2, 4, 8])
@pytest.mark.parametrize("n,k", [(256, 1536), (1536, 1536), (1536, 6912)])
def test_bf16_gemv_matches_small_decode_batches(m, n, k):
torch.manual_seed(19 + m)
x = torch.randn(m, k, device="cuda", dtype=torch.bfloat16)
weight = torch.randn(n, k, device="cuda", dtype=torch.bfloat16)
actual = bf16_gemv(x, weight)
expected = F.linear(x, weight)
assert actual.shape == (m, n)
torch.testing.assert_close(actual, expected, rtol=0.02, atol=0.5)
@skip_no_gemv
def test_bf16_gemv_preserves_singleton_batch_and_fuses_bias():
torch.manual_seed(23)
x = torch.randn(1, 1536, device="cuda", dtype=torch.bfloat16)
weight = torch.randn(1536, 1536, device="cuda", dtype=torch.bfloat16)
bias = torch.randn(1536, device="cuda", dtype=torch.bfloat16)
actual = bf16_gemv(x, weight, bias)
expected = F.linear(x, weight, bias)
assert actual.shape == (1, 1536)
torch.testing.assert_close(actual, expected, rtol=0.02, atol=0.25)
@skip_no_gemv
def test_bf16_gemv_small_batch_fuses_bias():
torch.manual_seed(25)
x = torch.randn(4, 1536, device="cuda", dtype=torch.bfloat16)
weight = torch.randn(256, 1536, device="cuda", dtype=torch.bfloat16)
bias = torch.randn(256, device="cuda", dtype=torch.bfloat16)
actual = bf16_gemv(x, weight, bias)
expected = F.linear(x, weight, bias)
torch.testing.assert_close(actual, expected, rtol=0.02, atol=0.25)
@skip_no_gemv
def test_bf16_gemv_uses_current_stream():
x = torch.randn(1536, device="cuda", dtype=torch.bfloat16)
weight = torch.randn(256, 1536, device="cuda", dtype=torch.bfloat16)
stream = torch.cuda.Stream()
with torch.cuda.stream(stream):
actual = bf16_gemv(x, weight)
expected = F.linear(x, weight)
stream.synchronize()
torch.testing.assert_close(actual, expected, rtol=0.02, atol=0.25)
@skip_no_gemv
def test_bf16_gemv_cuda_graph_replay():
torch.manual_seed(29)
x = torch.randn(1536, device="cuda", dtype=torch.bfloat16)
weight = torch.randn(1536, 1536, device="cuda", dtype=torch.bfloat16)
for _ in range(3):
bf16_gemv(x, weight)
graph = torch.cuda.CUDAGraph()
with torch.cuda.graph(graph):
actual = bf16_gemv(x, weight)
x.copy_(torch.randn_like(x))
graph.replay()
expected = F.linear(x, weight)
torch.testing.assert_close(actual, expected, rtol=0.02, atol=0.25)
@skip_no_gemv
def test_bf16_gemv_small_batch_cuda_graph_replay():
torch.manual_seed(31)
x = torch.randn(8, 1536, device="cuda", dtype=torch.bfloat16)
weight = torch.randn(1536, 1536, device="cuda", dtype=torch.bfloat16)
for _ in range(3):
bf16_gemv(x, weight)
graph = torch.cuda.CUDAGraph()
with torch.cuda.graph(graph):
actual = bf16_gemv(x, weight)
x.copy_(torch.randn_like(x))
graph.replay()
expected = F.linear(x, weight)
torch.testing.assert_close(actual, expected, rtol=0.02, atol=0.25)
@skip_no_gemv
@pytest.mark.parametrize(
"make_args,error",
[
(
lambda: (
torch.randn(3, 16, device="cuda", dtype=torch.bfloat16),
torch.randn(8, 16, device="cuda", dtype=torch.bfloat16),
),
"M must",
),
(
lambda: (
torch.randn(15, device="cuda", dtype=torch.bfloat16),
torch.randn(8, 15, device="cuda", dtype=torch.bfloat16),
),
"even",
),
(
lambda: (
torch.randn(16, device="cuda", dtype=torch.float16),
torch.randn(8, 16, device="cuda", dtype=torch.float16),
),
"bf16",
),
(
lambda: (
torch.randn(
16, device="cuda", dtype=torch.bfloat16, requires_grad=True
),
torch.randn(8, 16, device="cuda", dtype=torch.bfloat16),
),
"autograd",
),
],
)
def test_bf16_gemv_rejects_unsupported_inputs(make_args, error):
with pytest.raises(RuntimeError, match=error):
bf16_gemv(*make_args())
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import logging
import pytest
import torch
import torch.nn.functional as F
from astrai.extension import explain, is_available, linear, op_backend
from astrai.extension.backend import linear as public_linear
from astrai.model.components.linear import Linear
GEMV_AVAILABLE = (
torch.cuda.is_available()
and is_available("bf16_gemv")
and torch.cuda.get_device_capability() >= (8, 0)
)
skip_no_gemv = pytest.mark.skipif(
not GEMV_AVAILABLE,
reason="BF16 GEMV requires a built kernel and compute capability 8.0+",
)
def test_linear_backend_is_public():
assert linear is public_linear
def test_model_linear_routes_through_backend(monkeypatch):
sentinel = torch.randn(2, 4)
def fake_linear(x, weight, bias):
assert x.shape == (2, 3)
assert weight.shape == (4, 3)
assert bias is None
return sentinel
monkeypatch.setattr("astrai.model.components.linear.linear", fake_linear)
layer = Linear(3, 4)
assert layer(torch.randn(2, 3)) is sentinel
def test_cpu_and_training_calls_fall_back_to_torch(monkeypatch):
monkeypatch.setenv("ASTRAI_GEMV", "1")
x = torch.randn(2, 8, requires_grad=True)
weight = torch.randn(4, 8, requires_grad=True)
actual = linear(x, weight)
expected = F.linear(x, weight)
torch.testing.assert_close(actual, expected)
actual.sum().backward()
assert x.grad is not None
assert weight.grad is not None
def test_invalid_mode_warns_and_uses_auto(monkeypatch, caplog):
monkeypatch.setenv("ASTRAI_GEMV", "invalid-test-mode")
with caplog.at_level(logging.WARNING):
trace = explain("linear", torch.randn(1, 8), torch.randn(4, 8))
assert "using auto" in caplog.text
assert "=> torch" in trace
@skip_no_gemv
def test_mode_zero_disables_gemv(monkeypatch):
monkeypatch.setenv("ASTRAI_GEMV", "0")
x = torch.randn(1, 1536, device="cuda", dtype=torch.bfloat16)
weight = torch.randn(1536, 1536, device="cuda", dtype=torch.bfloat16)
with torch.no_grad():
assert "=> torch" in explain("linear", x, weight)
torch.testing.assert_close(linear(x, weight), F.linear(x, weight))
@skip_no_gemv
def test_mode_one_forces_capable_unmeasured_shape(monkeypatch):
monkeypatch.setenv("ASTRAI_GEMV", "1")
x = torch.randn(1, 64, device="cuda", dtype=torch.bfloat16)
weight = torch.randn(32, 64, device="cuda", dtype=torch.bfloat16)
with torch.no_grad():
assert "=> gemv" in explain("linear", x, weight)
torch.testing.assert_close(
linear(x, weight), F.linear(x, weight), rtol=0.02, atol=0.25
)
@skip_no_gemv
@pytest.mark.parametrize("m", [2, 4, 8])
def test_mode_one_dispatches_supported_small_batches(monkeypatch, m):
monkeypatch.setenv("ASTRAI_GEMV", "1")
x = torch.randn(m, 1536, device="cuda", dtype=torch.bfloat16)
weight = torch.randn(256, 1536, device="cuda", dtype=torch.bfloat16)
with torch.no_grad():
assert "=> gemv" in explain("linear", x, weight)
torch.testing.assert_close(
linear(x, weight), F.linear(x, weight), rtol=0.02, atol=0.25
)
@skip_no_gemv
def test_auto_m1_falls_back_until_end_to_end_gate_passes(monkeypatch):
monkeypatch.setenv("ASTRAI_GEMV", "auto")
x = torch.randn(1, 1536, device="cuda", dtype=torch.bfloat16)
winning = torch.randn(
1536,
1536,
device="cuda",
dtype=torch.bfloat16,
requires_grad=True,
)
with torch.no_grad():
assert "=> torch" in explain("linear", x, winning)
torch.testing.assert_close(linear(x, winning), F.linear(x, winning))
@skip_no_gemv
def test_auto_selects_measured_sm89_small_batch_winner(monkeypatch):
monkeypatch.setenv("ASTRAI_GEMV", "auto")
x = torch.randn(4, 1536, device="cuda", dtype=torch.bfloat16)
weight = torch.randn(256, 1536, device="cuda", dtype=torch.bfloat16)
with torch.no_grad():
trace = explain("linear", x, weight)
if torch.cuda.get_device_capability() == (8, 9):
assert "=> auto_gemv" in trace
else:
assert "=> torch" in trace
torch.testing.assert_close(
linear(x, weight), F.linear(x, weight), rtol=0.02, atol=0.5
)
@skip_no_gemv
@pytest.mark.parametrize(
"m,n,k",
[
(2, 6912, 1536), # up/gate loses at every measured M
(2, 1536, 6912), # long-K accumulation changed checkpoint greedy output
(4, 100000, 1536), # LM head misses the 5% M=4 gate
(4, 1536, 6912), # long-K accumulation changed checkpoint greedy output
(8, 256, 1536), # remaining M=8 winners miss the 3% end-to-end gate
],
)
def test_auto_rejects_measured_small_batch_losers(monkeypatch, m, n, k):
monkeypatch.setenv("ASTRAI_GEMV", "auto")
x = torch.randn(m, k, device="cuda", dtype=torch.bfloat16)
weight = torch.randn(n, k, device="cuda", dtype=torch.bfloat16)
with torch.no_grad():
assert "=> torch" in explain("linear", x, weight)
@skip_no_gemv
def test_grad_enabled_and_unsupported_multirow_always_fall_back(monkeypatch):
monkeypatch.setenv("ASTRAI_GEMV", "1")
x = torch.randn(1, 1536, device="cuda", dtype=torch.bfloat16)
weight = torch.randn(
256, 1536, device="cuda", dtype=torch.bfloat16, requires_grad=True
)
assert "=> torch" in explain("linear", x, weight)
with torch.no_grad():
multirow = x.expand(3, -1).contiguous()
assert "=> torch" in explain("linear", multirow, weight)
@skip_no_gemv
def test_explicit_gemv_selection_respects_capability(monkeypatch):
monkeypatch.setenv("ASTRAI_GEMV", "0")
x = torch.randn(1, 1536, device="cuda", dtype=torch.bfloat16)
weight = torch.randn(256, 1536, device="cuda", dtype=torch.bfloat16)
with torch.no_grad(), op_backend(linear="gemv"):
assert "=> gemv" in explain("linear", x, weight)
torch.testing.assert_close(
linear(x, weight), F.linear(x, weight), rtol=0.02, atol=0.25
)
@skip_no_gemv
def test_dispatched_linear_cuda_graph_replay(monkeypatch):
monkeypatch.setenv("ASTRAI_GEMV", "1")
x = torch.randn(1, 1536, device="cuda", dtype=torch.bfloat16)
weight = torch.randn(256, 1536, device="cuda", dtype=torch.bfloat16)
with torch.no_grad():
for _ in range(3):
linear(x, weight)
graph = torch.cuda.CUDAGraph()
with torch.cuda.graph(graph):
actual = linear(x, weight)
x.copy_(torch.randn_like(x))
graph.replay()
expected = F.linear(x, weight)
torch.testing.assert_close(actual, expected, rtol=0.02, atol=0.25)