Files
sglang/python/sglang/jit_kernel/kvcache.py
2026-01-10 17:34:09 -08:00

85 lines
2.1 KiB
Python

from __future__ import annotations
import logging
from typing import TYPE_CHECKING
import torch
from sglang.jit_kernel.utils import (
cache_once,
is_arch_support_pdl,
load_jit,
make_cpp_args,
)
if TYPE_CHECKING:
from tvm_ffi.module import Module
@cache_once
def _jit_kvcache_module(row_bytes: int) -> Module:
args = make_cpp_args(row_bytes, is_arch_support_pdl())
return load_jit(
"kvcache",
*args,
cuda_files=["elementwise/kvcache.cuh"],
cuda_wrappers=[("store_cache", f"StoreKVCacheKernel<{args}>::run")],
)
@cache_once
def can_use_store_cache(size: int) -> bool:
logger = logging.getLogger(__name__)
if size % 4 != 0:
logger.warning(
f"Unsupported row_bytes={size} for JIT KV-Cache kernel:"
" must be multiple of 4"
)
return False
try:
_jit_kvcache_module(size)
return True
except Exception as e:
logger.warning(
f"Failed to load JIT KV-Cache kernel " f"with row_bytes={size}: {e}"
)
return False
def store_cache(
k: torch.Tensor,
v: torch.Tensor,
k_cache: torch.Tensor,
v_cache: torch.Tensor,
indices: torch.Tensor,
*,
row_bytes: int = 0,
num_split: int = 0, # can be tuned for performance
) -> None:
"""Store key and value tensors into KV cache at specified indices.
Args:
k (torch.Tensor): Key tensor of shape (batch_size, H * D).
v (torch.Tensor): Value tensor of shape (batch_size, H * D).
k_cache (torch.Tensor): Key cache tensor of shape (num_pages, H * D).
v_cache (torch.Tensor): Value cache tensor of shape (num_pages, H * D).
indices (torch.Tensor): Indices tensor of shape (batch_size,).
"""
row_bytes = row_bytes or k.shape[-1] * k.element_size()
module = _jit_kvcache_module(row_bytes)
if num_split <= 0:
if row_bytes % 2048 == 0:
num_split = 4
elif row_bytes % 1024 == 0:
num_split = 2
else:
num_split = 1
module.store_cache(
k,
v,
k_cache,
v_cache,
indices,
num_split,
)