test_kvcacheio.py

import pytest
import torch
from sgl_kernel.kvcacheio import (
    transfer_kv_all_layer,
    transfer_kv_all_layer_mla,
    transfer_kv_per_layer,
    transfer_kv_per_layer_mla,
)


def ref_copy_with_indices(src_pool, dst_pool, src_indices, dst_indices):
    dst_pool[dst_indices] = src_pool[src_indices].to(dst_pool.device)


@pytest.mark.parametrize("dtype", [torch.bfloat16, torch.float16])
@pytest.mark.parametrize("num_items_to_transfer", [1, 128, 1024])
@pytest.mark.parametrize("page_size", [1, 16, 64])
@pytest.mark.parametrize("item_size", [256])
@pytest.mark.parametrize("total_items_in_pool", [10240])
@pytest.mark.parametrize("is_mla", [False, True])
@pytest.mark.parametrize("all_layers", [False, True])
def test_transfer_kv(
    dtype: torch.dtype,
    num_items_to_transfer: int,
    item_size: int,
    page_size: int,
    total_items_in_pool: int,
    is_mla: bool,
    all_layers: bool,
):
    """
    Tests the per-layer transfer functions, treating tensors as memory pools.
    """

    original_dtype = torch.get_default_dtype()
    torch.set_default_dtype(dtype)
    device = "cuda"
    torch.cuda.manual_seed(42)

    num_layers = 4  # A small number of layers for pool creation

    total_pages_in_pool = total_items_in_pool // page_size
    num_pages_to_transfer = num_items_to_transfer // page_size
    if num_pages_to_transfer == 0:
        torch.set_default_dtype(original_dtype)
        return
    page_indices = torch.randperm(total_pages_in_pool, dtype=torch.int64)
    src_indices_host = torch.cat(
        [
            torch.arange(p * page_size, (p + 1) * page_size)
            for p in page_indices[:num_pages_to_transfer]
        ]
    )
    src_indices_device = src_indices_host.to(device)
    dst_indices_host = torch.cat(
        [
            torch.arange(p * page_size, (p + 1) * page_size)
            for p in page_indices[num_pages_to_transfer : 2 * num_pages_to_transfer]
        ]
    )
    dst_indices_device = dst_indices_host.to(device)

    # Prepare memory pools based on whether it's an MLA case.
    if is_mla:
        src_pool_host = torch.randn(
            num_layers, total_items_in_pool, item_size
        ).pin_memory()
        dst_pool_ref = torch.zeros_like(src_pool_host).to(device)
        dst_pool_kernel = torch.zeros_like(dst_pool_ref)
        dst_pool_direct = torch.zeros_like(dst_pool_ref)
    else:
        src_k_pool = torch.randn(
            num_layers, total_items_in_pool, item_size
        ).pin_memory()
        src_v_pool = torch.randn(
            num_layers, total_items_in_pool, item_size
        ).pin_memory()
        dst_k_pool_ref = torch.zeros_like(src_k_pool).to(device)
        dst_v_pool_ref = torch.zeros_like(src_v_pool).to(device)
        dst_k_pool_kernel = torch.zeros_like(dst_k_pool_ref)
        dst_v_pool_kernel = torch.zeros_like(dst_v_pool_ref)
        dst_k_pool_direct = torch.zeros_like(dst_k_pool_ref)
        dst_v_pool_direct = torch.zeros_like(dst_v_pool_ref)

    torch.cuda.synchronize()

    # We will test the per-layer function on the first layer (index 0) of the pool.
    layer_idx_to_test = 0

    if is_mla:
        if not all_layers:
            ref_copy_with_indices(
                src_pool_host[layer_idx_to_test],
                dst_pool_ref[layer_idx_to_test],
                src_indices_host,
                dst_indices_device,
            )
            transfer_kv_per_layer_mla(
                src_pool_host[layer_idx_to_test],
                dst_pool_kernel[layer_idx_to_test],
                src_indices_device,
                dst_indices_device,
                io_backend="kernel",
                page_size=page_size,
                item_size=item_size,
            )
            transfer_kv_per_layer_mla(
                src_pool_host[layer_idx_to_test],
                dst_pool_direct[layer_idx_to_test],
                src_indices_host,
                dst_indices_device,
                io_backend="direct",
                page_size=page_size,
                item_size=item_size,
            )
        else:
            for layer_id in range(num_layers):
                ref_copy_with_indices(
                    src_pool_host[layer_id],
                    dst_pool_ref[layer_id],
                    src_indices_host,
                    dst_indices_device,
                )
            transfer_kv_all_layer_mla(
                src_pool_host,
                dst_pool_kernel,
                src_indices_device,
                dst_indices_device,
                io_backend="kernel",
                page_size=page_size,
                item_size=item_size,
                num_layers=num_layers,
                src_layer_offset=total_items_in_pool * item_size,
                dst_layer_offset=total_items_in_pool * item_size,
            )
            transfer_kv_all_layer_mla(
                src_pool_host,
                dst_pool_direct,
                src_indices_host,
                dst_indices_device,
                io_backend="direct",
                page_size=page_size,
                item_size=item_size,
                num_layers=num_layers,
                src_layer_offset=total_items_in_pool * item_size,
                dst_layer_offset=total_items_in_pool * item_size,
            )
        torch.cuda.synchronize()
        torch.testing.assert_close(dst_pool_kernel, dst_pool_ref)
        torch.testing.assert_close(dst_pool_direct, dst_pool_ref)
    else:
        if not all_layers:
            ref_copy_with_indices(
                src_k_pool[layer_idx_to_test],
                dst_k_pool_ref[layer_idx_to_test],
                src_indices_host,
                dst_indices_device,
            )
            ref_copy_with_indices(
                src_v_pool[layer_idx_to_test],
                dst_v_pool_ref[layer_idx_to_test],
                src_indices_host,
                dst_indices_device,
            )
            transfer_kv_per_layer(
                src_k_pool[layer_idx_to_test],
                dst_k_pool_kernel[layer_idx_to_test],
                src_v_pool[layer_idx_to_test],
                dst_v_pool_kernel[layer_idx_to_test],
                src_indices_device,
                dst_indices_device,
                io_backend="kernel",
                page_size=page_size,
                item_size=item_size,
            )
            transfer_kv_per_layer(
                src_k_pool[layer_idx_to_test],
                dst_k_pool_direct[layer_idx_to_test],
                src_v_pool[layer_idx_to_test],
                dst_v_pool_direct[layer_idx_to_test],
                src_indices_host,
                dst_indices_device,
                io_backend="direct",
                page_size=page_size,
                item_size=item_size,
            )
        else:
            for layer_id in range(num_layers):
                ref_copy_with_indices(
                    src_k_pool[layer_id],
                    dst_k_pool_ref[layer_id],
                    src_indices_host,
                    dst_indices_device,
                )
                ref_copy_with_indices(
                    src_v_pool[layer_id],
                    dst_v_pool_ref[layer_id],
                    src_indices_host,
                    dst_indices_device,
                )
            transfer_kv_all_layer(
                src_k_pool,
                dst_k_pool_kernel,
                src_v_pool,
                dst_v_pool_kernel,
                src_indices_device,
                dst_indices_device,
                io_backend="kernel",
                page_size=page_size,
                item_size=item_size,
                num_layers=num_layers,
                src_layer_offset=total_items_in_pool * item_size,
                dst_layer_offset=total_items_in_pool * item_size,
            )
            transfer_kv_all_layer(
                src_k_pool,
                dst_k_pool_direct,
                src_v_pool,
                dst_v_pool_direct,
                src_indices_host,
                dst_indices_device,
                io_backend="direct",
                page_size=page_size,
                item_size=item_size,
                num_layers=num_layers,
                src_layer_offset=total_items_in_pool * item_size,
                dst_layer_offset=total_items_in_pool * item_size,
            )
        torch.cuda.synchronize()
        torch.testing.assert_close(dst_k_pool_kernel, dst_k_pool_ref)
        torch.testing.assert_close(dst_v_pool_kernel, dst_v_pool_ref)
        torch.testing.assert_close(dst_k_pool_direct, dst_k_pool_ref)
        torch.testing.assert_close(dst_v_pool_direct, dst_v_pool_ref)

    torch.set_default_dtype(original_dtype)


if __name__ == "__main__":
    pytest.main([__file__])