Skip to content

Instantly share code, notes, and snippets.

@vwxyzjn

vwxyzjn/test_low_latency_roce.py

Last active September 24, 2025 05:06
Show Gist options

  • Select an option

    Learn more about clone URLs
  • Save vwxyzjn/0e7d1bcbffe516c10ecd8edebc3b9371 to your computer and use it in GitHub Desktop.

Select an option

Learn more about clone URLs
Save vwxyzjn/0e7d1bcbffe516c10ecd8edebc3b9371 to your computer and use it in GitHub Desktop.
Download ZIP
Raw
test_low_latency_roce.py
import argparse
import random
import time
import os
import torch
import torch.distributed as dist
import numpy as np
from functools import partial
from typing import Optional
import deep_ep
from utils import init_dist, bench, bench_kineto, calc_diff, hash_tensor, per_token_cast_back
def test_main(num_tokens: int, hidden: int, num_experts: int, num_topk: int,
rank: int, num_ranks: int, group: dist.ProcessGroup, buffer: deep_ep.Buffer,
use_logfmt: bool = False, seed: int = 0):
torch.manual_seed(seed + rank)
random.seed(seed + rank)
assert num_experts % num_ranks == 0
num_local_experts = num_experts // num_ranks
# NOTES: the integers greater than 256 exceed the BF16 precision limit
rank_offset = 128
assert num_ranks - rank_offset < 257, 'Too many ranks (exceeding test precision limit)'
x = torch.ones((num_tokens, hidden), dtype=torch.bfloat16, device='cuda') * (rank - rank_offset)
x[:, -128:] = torch.arange(num_tokens, device='cuda').to(torch.bfloat16).view(-1, 1)
x_list = [x]
for i in range(4 if use_logfmt else 0):
# NOTES: make more LogFMT casts and also with some BF16
x_list.append(torch.randn((num_tokens, hidden), dtype=torch.bfloat16, device='cuda') * 0.5 * random.random())
# NOTES: the last one is for performance testing
# Most of the values in the perf case is lower than the threshold, casting most channels
x_list.append(torch.randn((num_tokens, hidden), dtype=torch.bfloat16, device='cuda') * 0.1)
scores = torch.randn((num_tokens, num_experts), dtype=torch.float32, device='cuda').abs() + 1
topk_idx = torch.topk(scores, num_topk, dim=-1, largest=True, sorted=True)[1]
topk_weights = torch.randn((num_tokens, num_topk), dtype=torch.float32, device='cuda').abs()
# Randomly mask some positions
for i in range(10):
topk_idx[random.randint(0, num_tokens - 1), random.randint(0, num_topk - 1)] = -1
# Check dispatch correctness
do_check = True
hash_value, num_times = 0, 0
for current_x in x_list:
for return_recv_hook in (False, True):
for dispatch_use_fp8 in (False, True):
for round_scale in (False, True) if dispatch_use_fp8 else (False, ):
for use_ue8m0 in (False, True) if round_scale else (False, ):
num_times += 1
for i in range((num_times % 2) + 1):
cumulative_local_expert_recv_stats = torch.zeros((num_local_experts, ), dtype=torch.int, device='cuda')
packed_recv_x, packed_recv_count, handle, event, hook = \
buffer.low_latency_dispatch(current_x, topk_idx, num_tokens, num_experts,
use_fp8=dispatch_use_fp8, round_scale=round_scale, use_ue8m0=use_ue8m0,
cumulative_local_expert_recv_stats=cumulative_local_expert_recv_stats,
async_finish=not return_recv_hook, return_recv_hook=return_recv_hook)
hook() if return_recv_hook else event.current_stream_wait()
packed_recv_x = (packed_recv_x[0], packed_recv_x[1].contiguous()) if dispatch_use_fp8 else packed_recv_x
simulated_gemm_x = per_token_cast_back(packed_recv_x[0].view(-1, hidden), packed_recv_x[1].view(-1, hidden // 128)).view(packed_recv_x[0].shape) \
if dispatch_use_fp8 else packed_recv_x.clone()
all_topk_idx = torch.empty((num_ranks, num_tokens, num_topk), dtype=topk_idx.dtype, device='cuda')
dist.all_gather_into_tensor(all_topk_idx, topk_idx, group=group)
for i in range(num_local_experts if do_check else 0):
expert_id = rank * num_local_experts + i
recv_x = per_token_cast_back(packed_recv_x[0][i], packed_recv_x[1][i]) if dispatch_use_fp8 else packed_recv_x[i]
recv_count, recv_src_info, recv_layout_range = packed_recv_count[i], handle[0][i], handle[1][i]
# Check expert indices
int_mask = (2 ** 32) - 1
num_valid_tokens = recv_count.item()
assert cumulative_local_expert_recv_stats[i].item() == num_valid_tokens, f'{cumulative_local_expert_recv_stats[i].item()} != {num_valid_tokens}'
assert num_valid_tokens == (recv_layout_range & int_mask).sum().item(), f'{num_valid_tokens} != {recv_layout_range & int_mask}.sum().item()'
assert num_valid_tokens == (all_topk_idx == expert_id).sum().item(), f'{num_valid_tokens} != {(all_topk_idx == expert_id).sum().item()}'
if num_valid_tokens == 0:
continue
# Check received data
if current_x is x:
recv_x = recv_x[:num_valid_tokens]
recv_x_amin = recv_x[:, :-128].amin(dim=-1)
recv_src_info = recv_src_info[:num_valid_tokens]
assert torch.equal(recv_x_amin, recv_x[:, :-128].amax(dim=-1))
if round_scale:
assert calc_diff(recv_x[:, -1], recv_src_info.view(-1)) < 0.007
else:
assert (recv_x[:, -128:] - recv_src_info.view(-1, 1) % num_tokens).sum().item() == 0
for j in range(num_ranks):
begin_idx, count = (recv_layout_range[j] >> 32).item(), (recv_layout_range[j] & int_mask).item()
if not round_scale:
assert (recv_x_amin == j - rank_offset).sum().item() == (all_topk_idx[j] == expert_id).sum().item()
assert (recv_x[begin_idx:begin_idx + count, :-128] - j + rank_offset).sum().item() == 0
if dispatch_use_fp8:
hash_value ^= hash_tensor(packed_recv_x[0][i, :num_valid_tokens])
hash_value ^= hash_tensor(packed_recv_x[1][i, :num_valid_tokens])
else:
hash_value ^= hash_tensor(packed_recv_x[i, :num_valid_tokens])
# Check combine correctness
for zero_copy in (False, ) if use_logfmt else (False, True):
if zero_copy:
buffer.get_next_low_latency_combine_buffer(handle)[:, :, :] = simulated_gemm_x
out = torch.empty((num_tokens, hidden), dtype=torch.bfloat16, device='cuda')
combined_x, event, hook = buffer.low_latency_combine(simulated_gemm_x, topk_idx, topk_weights, handle,
use_logfmt=use_logfmt,
async_finish=not return_recv_hook, zero_copy=zero_copy,
return_recv_hook=return_recv_hook, out=out)
hook() if return_recv_hook else event.current_stream_wait()
if do_check:
diff = calc_diff(current_x * topk_weights.masked_fill(topk_idx == -1, 0).sum(dim=1).view(-1, 1), combined_x)
assert torch.isnan(combined_x).sum().item() == 0
# assert diff < (9e-4 if dispatch_use_fp8 else 1e-5), f'Error: {diff=}, {dispatch_use_fp8=}, {zero_copy=}'
hash_value ^= hash_tensor(combined_x)
# noinspection PyShadowingNames
def large_gemm_with_hook(hook):
mat_0 = torch.randn((8192, 8192), dtype=torch.float)
mat_1 = torch.randn((8192, 8192), dtype=torch.float)
mat_0 @ mat_1
hook()
# noinspection PyShadowingNames
def test_func(return_recv_hook: bool):
recv_x, recv_count, handle, event, hook = \
buffer.low_latency_dispatch(current_x, topk_idx, num_tokens, num_experts,
cumulative_local_expert_recv_stats=cumulative_local_expert_recv_stats,
use_fp8=True, async_finish=False, return_recv_hook=return_recv_hook)
large_gemm_with_hook(hook) if return_recv_hook else None
combined_x, event, hook = buffer.low_latency_combine(simulated_gemm_x, topk_idx, topk_weights, handle,
use_logfmt=use_logfmt, return_recv_hook=return_recv_hook)
large_gemm_with_hook(hook) if return_recv_hook else None
# Calculate bandwidth
num_fp8_bytes, num_bf16_bytes = (hidden + hidden / 128 * 4 + 16), hidden * 2
num_logfmt10_bytes = hidden * 10 / 8 + hidden / 128 * 4
num_dispatch_comm_bytes, num_combine_comm_bytes = 0, 0
for i in range(num_tokens):
num_selections = (topk_idx[i] != -1).sum().item()
num_dispatch_comm_bytes += num_fp8_bytes * num_selections
num_combine_comm_bytes += (num_logfmt10_bytes if use_logfmt else num_bf16_bytes) * num_selections
# Dispatch + combine testing
avg_t, min_t, max_t = bench(partial(test_func, return_recv_hook=False))
print(f'[rank {rank}] Dispatch + combine bandwidth: {(num_dispatch_comm_bytes + num_combine_comm_bytes) / 1e9 / avg_t:.2f} GB/s, '
f'avg_t={avg_t * 1e6:.2f} us, min_t={min_t * 1e6:.2f} us, max_t={max_t * 1e6:.2f} us', flush=True)
# Separate profiling
for return_recv_hook in (False, True):
group.barrier()
dispatch_t, combine_t = bench_kineto(partial(test_func, return_recv_hook=return_recv_hook),
kernel_names=('dispatch', 'combine'), barrier_comm_profiling=True,
suppress_kineto_output=True, num_kernels_per_period=2 if return_recv_hook else 1)
if not return_recv_hook:
print(f'[rank {rank}] Dispatch bandwidth: {num_dispatch_comm_bytes / 1e9 / dispatch_t:.2f} GB/s, avg_t={dispatch_t * 1e6:.2f} us | '
f'Combine bandwidth: {num_combine_comm_bytes / 1e9 / combine_t:.2f} GB/s, avg_t={combine_t * 1e6:.2f} us', flush=True)
else:
print(f'[rank {rank}] Dispatch send/recv time: {dispatch_t[0] * 1e6:.2f} + {dispatch_t[1] * 1e6:.2f} us | '
f'Combine send/recv time: {combine_t[0] * 1e6:.2f} + {combine_t[1] * 1e6:.2f} us', flush=True)
return hash_value
# noinspection PyUnboundLocalVariable,PyShadowingNames
def test_loop(local_rank: int, num_local_ranks: int, args: argparse.Namespace):
os.environ['NVSHMEM_ENABLE_NIC_PE_MAPPING'] = '1'
os.environ['NVSHMEM_HCA_LIST'] = f'mlx5_{local_rank}:1'
rank, num_ranks, group = init_dist(local_rank, num_local_ranks)
num_tokens, hidden = args.num_tokens, args.hidden
num_topk, num_experts = args.num_topk, args.num_experts
num_rdma_bytes = deep_ep.Buffer.get_low_latency_rdma_size_hint(num_tokens, hidden, num_ranks, num_experts)
if local_rank == 0:
print(f'Allocating buffer size: {num_rdma_bytes / 1e6} MB ...', flush=True)
buffer = deep_ep.Buffer(group, num_rdma_bytes=num_rdma_bytes, low_latency_mode=True,
num_qps_per_rank=num_experts // num_ranks,
allow_nvlink_for_low_latency_mode=not args.disable_nvlink, explicitly_destroy=True,
allow_mnnvl=args.allow_mnnvl)
test_main(num_tokens, hidden, num_experts, num_topk, rank, num_ranks, group, buffer,
use_logfmt=args.use_logfmt, seed=1)
do_pressure_test = args.pressure_test
for seed in range(int(1e9) if do_pressure_test else 0):
if local_rank == 0:
print(f'Testing with seed {seed} ...', flush=True)
ref_hash = test_main(num_tokens, hidden, num_experts, num_topk, rank, num_ranks, group, buffer,
use_logfmt=args.use_logfmt, seed=seed)
for i in range(20):
assert test_main(num_tokens, hidden, num_experts, num_topk, rank, num_ranks, group, buffer,
use_logfmt=args.use_logfmt, seed=seed) == ref_hash, f'Error: seed={seed}'
# Destroy the buffer runtime and communication group
buffer.destroy()
dist.barrier()
dist.destroy_process_group()
if __name__ == '__main__':
# TODO: you may modify NUMA binding for less CPU overhead
# TODO: buggy with `num_tokens=512`
parser = argparse.ArgumentParser(description='Test low-latency EP kernels')
parser.add_argument('--num-processes', type=int, default=8,
help='Number of processes to spawn (default: 8)')
parser.add_argument('--num-tokens', type=int, default=128,
help='Number of tokens (default: 128)')
parser.add_argument('--hidden', type=int, default=7168,
help='Hidden dimension size (default: 7168)')
parser.add_argument('--num-topk', type=int, default=8,
help='Number of top-k experts (default: 8)')
parser.add_argument('--num-experts', type=int, default=288,
help='Number of experts (default: 288)')
parser.add_argument('--allow-mnnvl', action="store_true",
help='Allow MNNVL for communication')
parser.add_argument('--disable-nvlink', action='store_true',
help='Whether to disable NVLink for testing')
parser.add_argument('--use-logfmt', action='store_true',
help='Whether to test LogFMT combine')
parser.add_argument("--pressure-test", action='store_true',
help='Whether to do pressure test')
args = parser.parse_args()
num_processes = args.num_processes
torch.multiprocessing.spawn(test_loop, args=(num_processes, args), nprocs=num_processes)
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment