@dataclass
class LoRAKernelMeta:
token_lora_mapping: torch.Tensor
token_indices_sorted_by_lora_ids: torch.Tensor
active_lora_ids: torch.Tensor
num_tokens_per_lora: torch.Tensor
lora_token_start_loc: torch.Tensor
# The V1 architecture uses the traced torch.compile graphs to execute
# a forward pass. Things to note about this process,
# 1. The tracing infers all python scalar datatype objects into a constant
# value.
# 2. The tracing cannot handle dynamic control flow. (dynamic control flow
# is an experimental feature in pytorch)
# 3. The internals of torch.ops functions are not traced.
# We disguise the "no_lora" flag as a cpu tensor and leverage point number 3
# to early exit from inside the lora_expand / lora_shrink torch operation.
no_lora_flag_cpu: torch.Tensor
@staticmethod
def make(max_loras: int, max_num_tokens: int,
device: Union[torch.device, str]) -> "LoRAKernelMeta":
token_lora_mapping = torch.empty(max_num_tokens,
dtype=torch.int32,
device=device)
token_indices_sorted_by_lora_ids = torch.empty(max_num_tokens,
dtype=torch.int32,
device=device)
# +1 because "no-lora" is also a possibility
# example: let max_loras be 3, active_lora_ids of [-1, 0, 2, 1]
# is a possibility.
active_lora_ids = torch.empty(max_loras + 1,
dtype=torch.int32,
device=device)
# using running example, [3, 10, 5, 2] is a possibility.
num_tokens_per_lora = torch.zeros(max_loras + 1,
dtype=torch.int32,
device=device)
# +2 for this because, the first index is always 0.
# using running example, lora_token_start_loc
# is [0, 3, 13, 18, 20].
lora_token_start_loc = torch.zeros(max_loras + 2,
dtype=torch.int32,
device=device)
no_lora_flag_cpu = torch.tensor([False],
dtype=torch.bool,
device='cpu')
return LoRAKernelMeta(
token_lora_mapping=token_lora_mapping,
token_indices_sorted_by_lora_ids=token_indices_sorted_by_lora_ids,
active_lora_ids=active_lora_ids,
num_tokens_per_lora=num_tokens_per_lora,
lora_token_start_loc=lora_token_start_loc,
no_lora_flag_cpu=no_lora_flag_cpu)
def _reset(self):
self.active_lora_ids.fill_(-1)
self.num_tokens_per_lora.fill_(0)
self.lora_token_start_loc.fill_(0)
self.no_lora_flag_cpu.fill_(False)
def prepare_tensors(self, token_lora_mapping: torch.Tensor) -> None:
"""
Prepare kernel metadata tensors for the current forward pass.
Args:
token_lora_tensor (torch.Tensor): Tensor containing lora indices
for each input token.
"""
self._reset()
# Check and record no-lora case.
no_lora = torch.all(token_lora_mapping == -1)
self.no_lora_flag_cpu[0] = no_lora
if no_lora:
# Early exit. LoRA kernels will not be run.
return
num_tokens = token_lora_mapping.size(0)
# copy token lora mapping
self.token_lora_mapping[:num_tokens].copy_(token_lora_mapping,
non_blocking=True)
# token_indices_sorted_by_lora_ids
_, token_indices_sorted_by_lora_ids = torch.sort(token_lora_mapping,
stable=True)
# start gpu transfer
self.token_indices_sorted_by_lora_ids[:num_tokens].copy_(
token_indices_sorted_by_lora_ids, non_blocking=True)
# active_lora_ids, num_tokens_per_lora
lora_ids, num_tokens_per_lora = torch.unique(token_lora_mapping,
sorted=True,
return_counts=True)
self.active_lora_ids[:lora_ids.size(0)].copy_(lora_ids,
non_blocking=True)
self.num_tokens_per_lora[:num_tokens_per_lora.size(0)].copy_(
num_tokens_per_lora, non_blocking=True)
# lora_token_start_loc
lora_token_start_loc = torch.cumsum(num_tokens_per_lora, dim=0)
self.lora_token_start_loc[1:1 + lora_token_start_loc.size(0)].copy_(
lora_token_start_loc, non_blocking=True)
def meta_args(
self, token_nums: int
) -> tuple[torch.Tensor, torch.Tensor, torch.Tensor, torch.Tensor,
torch.Tensor, torch.Tensor]:
"""
This function returns the kernel metadata required for the current
forward pass execution of the kernel. The function returns all the
metadata required by the kernel, in order, as a tuple, so it can be
unpacked directly during the lora_shrink/lora_expand function call.
Args:
token_nums (int): Number of input tokens in the current forward
pass.
"""
return (
self.token_lora_mapping[:token_nums],
self.token_indices_sorted_by_lora_ids[:token_nums],
self.num_tokens_per_lora,
self.lora_token_start_loc,
self.active_lora_ids,
self.no_lora_flag_cpu,
)