Support tuning DeepEP configs (#6742)

benchmark/kernels/deepep/deepep_utils.py

+# ADAPTED FROM https://github.com/deepseek-ai/DeepEP/blob/main/tests/utils.py
+
+import os
+import sys
+from typing import Optional
+
+import numpy as np
+import torch
+import torch.distributed as dist
+
+
+def init_dist(local_rank: int, num_local_ranks: int, args):
+    ip = args.master_addr
+    port = args.master_port
+    num_nodes = args.nnodes
+    node_rank = args.node_rank
+    assert (num_local_ranks < 8 and num_nodes == 1) or num_local_ranks == 8
+
+    dist.init_process_group(
+        backend="nccl",
+        init_method=f"tcp://{ip}:{port}",
+        world_size=num_nodes * num_local_ranks,
+        rank=node_rank * num_local_ranks + local_rank,
+    )
+    torch.set_default_dtype(torch.bfloat16)
+    torch.set_default_device("cuda")
+    torch.cuda.set_device(local_rank)
+
+    return (
+        dist.get_rank(),
+        dist.get_world_size(),
+        dist.new_group(list(range(num_local_ranks * num_nodes))),
+    )
+
+
+def calc_diff(x: torch.Tensor, y: torch.Tensor):
+    x, y = x.double() + 1, y.double() + 1
+    denominator = (x * x + y * y).sum()
+    sim = 2 * (x * y).sum() / denominator
+    return (1 - sim).item()
+
+
+def per_token_cast_to_fp8(x: torch.Tensor):
+    assert x.dim() == 2 and x.size(1) % 128 == 0
+    m, n = x.shape
+    x_view = x.view(m, -1, 128)
+    x_amax = x_view.abs().float().amax(dim=2).view(m, -1).clamp(1e-4)
+    return (x_view * (448.0 / x_amax.unsqueeze(2))).to(torch.float8_e4m3fn).view(
+        m, n
+    ), (x_amax / 448.0).view(m, -1)
+
+
+def per_token_cast_back(x_fp8: torch.Tensor, x_scales: torch.Tensor):
+    x_fp32 = x_fp8.to(torch.float32).view(x_fp8.size(0), -1, 128)
+    x_scales = x_scales.view(x_fp8.size(0), -1, 1)
+    return (x_fp32 * x_scales).view(x_fp8.shape).to(torch.bfloat16)
+
+
+def inplace_unique(x: torch.Tensor, num_slots: int):
+    assert x.dim() == 2
+    mask = x < 0
+    x_padded = x.masked_fill(mask, num_slots)
+    bin_count = torch.zeros((x.size(0), num_slots + 1), dtype=x.dtype, device=x.device)
+    bin_count.scatter_add_(1, x_padded, torch.ones_like(x_padded))
+    bin_count = bin_count[:, :num_slots]
+    sorted_bin_count, sorted_bin_idx = torch.sort(bin_count, dim=-1, descending=True)
+    sorted_bin_idx.masked_fill_(sorted_bin_count == 0, -1)
+    sorted_bin_idx = torch.sort(sorted_bin_idx, descending=True, dim=-1).values
+    x[:, :].fill_(-1)
+    valid_len = min(num_slots, x.size(1))
+    x[:, :valid_len] = sorted_bin_idx[:, :valid_len]
+
+
+def create_grouped_scores(
+    scores: torch.Tensor, group_idx: torch.Tensor, num_groups: int
+):
+    num_tokens, num_experts = scores.shape
+    scores = scores.view(num_tokens, num_groups, -1)
+    mask = torch.zeros((num_tokens, num_groups), dtype=torch.bool, device=scores.device)
+    mask = mask.scatter_(1, group_idx, True).unsqueeze(-1).expand_as(scores)
+    return (scores * mask).view(num_tokens, num_experts)
+
+
+def bench(fn, num_warmups: int = 20, num_tests: int = 30, post_fn=None):
+    # Flush L2 cache with 256 MB data
+    torch.cuda.synchronize()
+    cache = torch.empty(int(256e6 // 4), dtype=torch.int, device="cuda")
+
+    # Warmup
+    for _ in range(num_warmups):
+        fn()
+
+    # Flush L2
+    cache.zero_()
+
+    # Testing
+    start_events = [torch.cuda.Event(enable_timing=True) for _ in range(num_tests)]
+    end_events = [torch.cuda.Event(enable_timing=True) for _ in range(num_tests)]
+    for i in range(num_tests):
+        # Record
+        start_events[i].record()
+        fn()
+        end_events[i].record()
+        if post_fn is not None:
+            post_fn()
+    torch.cuda.synchronize()
+
+    times = np.array(
+        [s.elapsed_time(e) / 1e3 for s, e in zip(start_events, end_events)]
+    )[1:]
+    return np.average(times), np.min(times), np.max(times)
+
+
+class empty_suppress:
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *_):
+        pass
+
+
+class suppress_stdout_stderr:
+    def __enter__(self):
+        self.outnull_file = open(os.devnull, "w")
+        self.errnull_file = open(os.devnull, "w")
+
+        self.old_stdout_fileno_undup = sys.stdout.fileno()
+        self.old_stderr_fileno_undup = sys.stderr.fileno()
+
+        self.old_stdout_fileno = os.dup(sys.stdout.fileno())
+        self.old_stderr_fileno = os.dup(sys.stderr.fileno())
+
+        self.old_stdout = sys.stdout
+        self.old_stderr = sys.stderr
+
+        os.dup2(self.outnull_file.fileno(), self.old_stdout_fileno_undup)
+        os.dup2(self.errnull_file.fileno(), self.old_stderr_fileno_undup)
+
+        sys.stdout = self.outnull_file
+        sys.stderr = self.errnull_file
+        return self
+
+    def __exit__(self, *_):
+        sys.stdout = self.old_stdout
+        sys.stderr = self.old_stderr
+
+        os.dup2(self.old_stdout_fileno, self.old_stdout_fileno_undup)
+        os.dup2(self.old_stderr_fileno, self.old_stderr_fileno_undup)
+
+        os.close(self.old_stdout_fileno)
+        os.close(self.old_stderr_fileno)
+
+        self.outnull_file.close()
+        self.errnull_file.close()
+
+
+def bench_kineto(
+    fn,
+    kernel_names,
+    num_tests: int = 30,
+    suppress_kineto_output: bool = False,
+    trace_path: Optional[str] = None,
+    barrier_comm_profiling: bool = False,
+):
+    # Profile
+    suppress = suppress_stdout_stderr if suppress_kineto_output else empty_suppress
+    with suppress():
+        schedule = torch.profiler.schedule(wait=0, warmup=1, active=1, repeat=1)
+        with torch.profiler.profile(
+            activities=[torch.profiler.ProfilerActivity.CUDA], schedule=schedule
+        ) as prof:
+            for i in range(2):
+                # NOTES: use a large kernel and a barrier to eliminate the unbalanced CPU launch overhead
+                if barrier_comm_profiling:
+                    lhs = torch.randn((8192, 8192), dtype=torch.float, device="cuda")
+                    rhs = torch.randn((8192, 8192), dtype=torch.float, device="cuda")
+                    lhs @ rhs
+                    dist.all_reduce(torch.ones(1, dtype=torch.float, device="cuda"))
+                for _ in range(num_tests):
+                    fn()
+                prof.step()
+
+    # Parse the profiling table
+    assert isinstance(kernel_names, str) or isinstance(kernel_names, tuple)
+    is_tupled = isinstance(kernel_names, tuple)
+    prof_lines = (
+        prof.key_averages()
+        .table(sort_by="cuda_time_total", max_name_column_width=100)
+        .split("\n")
+    )
+    kernel_names = (kernel_names,) if isinstance(kernel_names, str) else kernel_names
+    assert all([isinstance(name, str) for name in kernel_names])
+    for name in kernel_names:
+        assert (
+            sum([name in line for line in prof_lines]) == 1
+        ), f"Errors of the kernel {name} in the profiling table"
+
+    # Save chrome traces
+    if trace_path is not None:
+        prof.export_chrome_trace(trace_path)
+
+    # Return average kernel times
+    units = {"ms": 1e3, "us": 1e6}
+    kernel_times = []
+    for name in kernel_names:
+        for line in prof_lines:
+            if name in line:
+                time_str = line.split()[-2]
+                for unit, scale in units.items():
+                    if unit in time_str:
+                        kernel_times.append(float(time_str.replace(unit, "")) / scale)
+                        break
+                break
+    return tuple(kernel_times) if is_tupled else kernel_times[0]
+
+
+def hash_tensor(t: torch.Tensor):
+    return t.view(torch.int64).sum().item()

benchmark/kernels/deepep/tuning_deepep.py

+# MODIFIED FROM https://github.com/deepseek-ai/DeepEP/blob/main/tests/test_internode.py
+
+"""
+Example usage:
+python tuning_deepep.py --nnodes 4 --node-rank $MY_NODE_RANK --master-addr 1.2.3.4
+Then check `deepep_tuned.json`
+"""
+
+import argparse
+import json
+import time
+from copy import deepcopy
+from pathlib import Path
+
+# noinspection PyUnresolvedReferences
+import deep_ep
+import torch
+import torch.distributed as dist
+from deepep_utils import (
+    bench,
+    calc_diff,
+    create_grouped_scores,
+    init_dist,
+    inplace_unique,
+    per_token_cast_back,
+    per_token_cast_to_fp8,
+)
+
+
+def test_main(
+    num_sms: int,
+    local_rank: int,
+    num_local_ranks: int,
+    num_ranks: int,
+    num_nodes: int,
+    rank: int,
+    buffer: deep_ep.Buffer,
+    group: dist.ProcessGroup,
+    args,
+):
+    # Settings
+    num_tokens, hidden, num_topk_groups, num_topk, num_experts = (
+        4096,
+        7168,
+        min(num_nodes, 4),
+        8,
+        (256 // num_ranks) * num_ranks,
+    )
+    assert num_experts % num_ranks == 0 and num_local_ranks == 8
+    if local_rank == 0:
+        print(
+            f"[config] num_tokens={num_tokens}, hidden={hidden}, num_topk_groups={num_topk_groups}, num_topk={num_topk}",
+            flush=True,
+        )
+
+    # Random data
+    x = torch.ones((num_tokens, hidden), dtype=torch.bfloat16, device="cuda") * rank
+    x_pure_rand = torch.randn((num_tokens, hidden), dtype=torch.bfloat16, device="cuda")
+    x_e4m3 = per_token_cast_to_fp8(x)
+    scores = (
+        torch.randn((num_tokens, num_experts), dtype=torch.float32, device="cuda").abs()
+        + 1
+    )
+    group_scores = scores.view(num_tokens, num_nodes, -1).amax(dim=-1)
+    group_idx = torch.topk(
+        group_scores, k=num_topk_groups, dim=-1, sorted=False
+    ).indices
+    masked_scores = create_grouped_scores(scores, group_idx, num_nodes)
+    topk_idx = torch.topk(masked_scores, num_topk, dim=-1, largest=True, sorted=False)[
+        1
+    ]
+    topk_weights = (
+        torch.ones((num_tokens, num_topk), dtype=torch.float32, device="cuda") * rank
+    )
+    topk_weights_pure_rand = torch.randn(
+        (num_tokens, num_topk), dtype=torch.float32, device="cuda"
+    )
+    rank_idx = topk_idx // (num_experts // num_ranks)
+    rank_idx.masked_fill_(topk_idx == -1, -1)
+    inplace_unique(rank_idx, num_ranks)
+    rdma_rank_idx = rank_idx // num_local_ranks
+    rdma_rank_idx.masked_fill_(rank_idx == -1, -1)
+    inplace_unique(rdma_rank_idx, num_nodes)
+
+    # RDMA dispatch counts
+    rdma_idx = topk_idx // (num_experts // num_nodes)
+    rdma_idx.masked_fill_(topk_idx == -1, -1)
+    inplace_unique(rdma_idx, num_nodes)
+    num_rdma_token_sent = rdma_idx.ne(-1).sum().item()
+
+    # Expert meta
+    num_tokens_per_expert = torch.zeros((num_experts,), dtype=torch.int, device="cuda")
+    for i in range(num_experts):
+        num_tokens_per_expert[i] = (topk_idx == i).sum()
+    gbl_num_tokens_per_expert = num_tokens_per_expert.clone()
+    dist.all_reduce(gbl_num_tokens_per_expert, group=group)
+
+    # Rank layout meta
+    num_tokens_per_rank = torch.empty((num_ranks,), dtype=torch.int, device="cuda")
+    num_tokens_per_rdma_rank = torch.empty((num_nodes,), dtype=torch.int, device="cuda")
+    token_idx_in_rank = torch.full(
+        (num_ranks, num_tokens), -1, dtype=torch.long, device="cuda"
+    )
+    for i in range(num_ranks):
+        num_tokens_per_rank[i] = (rank_idx == i).sum()
+        token_sel = (rank_idx == i).max(dim=-1)[0]
+        count = token_sel.sum().item()
+        tokens = torch.sort(token_sel.to(torch.int), descending=True)[1]
+        tokens[:count] = torch.sort(tokens[:count])[0]
+        token_idx_in_rank[i][tokens[:count]] = torch.arange(
+            count, dtype=torch.long, device="cuda"
+        )
+    for i in range(num_nodes):
+        num_tokens_per_rdma_rank[i] = (rdma_rank_idx == i).sum()
+    token_idx_in_rank = token_idx_in_rank.T.contiguous().to(torch.int)
+    is_token_in_rank = token_idx_in_rank >= 0
+    gbl_num_tokens_per_rank = num_tokens_per_rank.clone()
+    dist.all_reduce(gbl_num_tokens_per_rank, group=group)
+
+    (
+        ref_num_tokens_per_rank,
+        ref_num_tokens_per_rdma_rank,
+        ref_num_tokens_per_expert,
+        ref_is_token_in_rank,
+        _,
+    ) = buffer.get_dispatch_layout(topk_idx, num_experts)
+    assert torch.allclose(ref_num_tokens_per_rank, num_tokens_per_rank)
+    assert torch.allclose(ref_num_tokens_per_rdma_rank, num_tokens_per_rdma_rank)
+    assert torch.allclose(ref_num_tokens_per_expert, num_tokens_per_expert)
+    assert torch.allclose(ref_is_token_in_rank, is_token_in_rank)
+    t = bench(lambda: buffer.get_dispatch_layout(topk_idx, num_experts))[0]
+    if local_rank == 0:
+        print(f"[layout] Kernel performance: {t * 1000:.3f} ms", flush=True)
+        print("", flush=True)
+    group.barrier()
+    time.sleep(1)
+
+    # Config
+    rdma_buffer_size, nvl_buffer_size = 128, (720 if num_ranks in (144, 160) else 512)
+    config = deep_ep.Config(num_sms, 8, nvl_buffer_size, 16, rdma_buffer_size)
+
+    # Test dispatch
+    # noinspection PyShadowingNames
+    def check_data(check_x, recv_gbl_rank_prefix_sum):
+        assert torch.allclose(check_x.amin(dim=1), check_x.amax(dim=1))
+        check_start = 0
+        for i in range(num_ranks):
+            check_end = recv_gbl_rank_prefix_sum[i].item()
+            assert (check_x[check_start:check_end, :].int() - i).sum().item() == 0
+            check_start = check_end
+
+    for previous_mode in (False, True):
+        for async_mode in (False, True):
+            for current_x in (x_pure_rand, x, x_e4m3):
+                for with_topk in (False, True):
+                    if local_rank == 0:
+                        print(
+                            f'[testing] Running with {"FP8" if isinstance(current_x, tuple) else "BF16"}, {"with" if with_topk else "without"} top-k (async={async_mode}, previous={previous_mode}) ...',
+                            flush=True,
+                            end="",
+                        )
+                    dispatch_args = {
+                        "x": current_x,
+                        "num_tokens_per_rank": num_tokens_per_rank,
+                        "num_tokens_per_rdma_rank": num_tokens_per_rdma_rank,
+                        "is_token_in_rank": is_token_in_rank,
+                        "num_tokens_per_expert": num_tokens_per_expert,
+                        "config": config,
+                        "async_finish": async_mode,
+                    }
+                    if with_topk:
+                        dispatch_args.update(
+                            {
+                                "topk_idx": topk_idx,
+                                "topk_weights": (
+                                    topk_weights_pure_rand
+                                    if current_x is x_pure_rand
+                                    else topk_weights
+                                ),
+                            }
+                        )
+                    if previous_mode:
+                        dispatch_args.update({"previous_event": buffer.capture()})
+                    (
+                        recv_x,
+                        recv_topk_idx,
+                        recv_topk_weights,
+                        recv_num_tokens_per_expert_list,
+                        handle,
+                        event,
+                    ) = buffer.dispatch(**dispatch_args)
+                    event.current_stream_wait() if async_mode else ()
+                    recv_x = (
+                        per_token_cast_back(*recv_x)
+                        if isinstance(recv_x, tuple)
+                        else recv_x
+                    )
+
+                    # Checks
+                    recv_gbl_rank_prefix_sum = handle[-4]
+                    assert gbl_num_tokens_per_rank[rank].item() == recv_x.size(
+                        0
+                    ), f"{gbl_num_tokens_per_rank[rank].item()} != {recv_x.size(0)}"
+                    assert (
+                        gbl_num_tokens_per_expert.view(num_ranks, -1)[rank].tolist()
+                        == recv_num_tokens_per_expert_list
+                    )
+                    if current_x is not x_pure_rand:
+                        check_data(recv_x, recv_gbl_rank_prefix_sum)
+                    if with_topk:
+                        # Check `topk_idx`
+                        assert (
+                            recv_topk_idx.eq(-1)
+                            | (
+                                (recv_topk_idx >= 0)
+                                & (recv_topk_idx < (num_experts // num_ranks))
+                            )
+                        ).sum().item() == recv_topk_idx.numel()
+                        for i, count in enumerate(recv_num_tokens_per_expert_list):
+                            assert recv_topk_idx.eq(i).sum().item() == count
+
+                        # Check `topk_weights`
+                        if current_x is not x_pure_rand:
+                            recv_topk_weights[recv_topk_idx.eq(-1)] = (
+                                recv_topk_weights.amax(dim=1, keepdim=True).expand_as(
+                                    recv_topk_weights
+                                )[recv_topk_idx.eq(-1)]
+                            )
+                            check_data(recv_topk_weights, recv_gbl_rank_prefix_sum)
+
+                    # Test cached dispatch (must without top-k staffs)
+                    if not with_topk:
+                        dispatch_args = {
+                            "x": current_x,
+                            "handle": handle,
+                            "config": config,
+                            "async_finish": async_mode,
+                        }
+                        if previous_mode:
+                            dispatch_args.update({"previous_event": buffer.capture()})
+                        recv_x, _, _, _, _, event = buffer.dispatch(**dispatch_args)
+                        event.current_stream_wait() if async_mode else ()
+                        recv_x = (
+                            per_token_cast_back(*recv_x)
+                            if isinstance(recv_x, tuple)
+                            else recv_x
+                        )
+                        if current_x is not x_pure_rand:
+                            check_data(recv_x, recv_gbl_rank_prefix_sum)
+
+                    # Test combine
+                    combine_args = {
+                        "x": recv_x,
+                        "handle": handle,
+                        "config": config,
+                        "async_finish": async_mode,
+                    }
+                    if with_topk:
+                        combine_args.update({"topk_weights": recv_topk_weights})
+                    if previous_mode:
+                        combine_args.update({"previous_event": buffer.capture()})
+                    combined_x, combined_topk_weights, event = buffer.combine(
+                        **combine_args
+                    )
+                    event.current_stream_wait() if async_mode else ()
+                    check_x = combined_x.float() / is_token_in_rank.sum(
+                        dim=1
+                    ).unsqueeze(1)
+                    ref_x = x_pure_rand if current_x is x_pure_rand else x
+                    assert calc_diff(check_x, ref_x) < 5e-6
+                    if with_topk:
+                        check_topk_weights = (
+                            combined_topk_weights
+                            if (current_x is x_pure_rand)
+                            else (
+                                combined_topk_weights
+                                / is_token_in_rank.sum(dim=1).unsqueeze(1)
+                            )
+                        )
+                        ref_topk_weights = (
+                            topk_weights_pure_rand
+                            if current_x is x_pure_rand
+                            else topk_weights
+                        )
+                        assert calc_diff(check_topk_weights, ref_topk_weights) < 1e-9
+
+                    # For later tuning
+                    dispatch_bf16_rdma_send_bytes = num_rdma_token_sent * hidden * 2
+                    dispatch_bf16_nvl_recv_bytes = recv_x.numel() * 2
+                    combine_bf16_nvl_send_bytes = dispatch_bf16_nvl_recv_bytes
+                    combine_bf16_rdma_recv_bytes = dispatch_bf16_rdma_send_bytes
+
+                    if local_rank == 0:
+                        print(" passed", flush=True)
+    if local_rank == 0:
+        print("", flush=True)
+
+    output_data = {}
+
+    # Tune dispatch performance
+    best_dispatch_results = None
+    fp8_factor = (1 + 4 / 128) / 2
+    for current_x in (x_e4m3, x):
+        best_time, best_results = 1e10, None
+        rdma_send_bytes = (
+            (dispatch_bf16_rdma_send_bytes * fp8_factor)
+            if isinstance(current_x, tuple)
+            else dispatch_bf16_rdma_send_bytes
+        )
+        nvl_recv_bytes = (
+            (dispatch_bf16_nvl_recv_bytes * fp8_factor)
+            if isinstance(current_x, tuple)
+            else dispatch_bf16_nvl_recv_bytes
+        )
+        for nvl_chunk_size in range(4, 33, 4):
+            for rdma_chunk_size in range(4, 33, 4):
+                config_kwargs = {
+                    "num_sms": num_sms,
+                    "num_max_nvl_chunked_send_tokens": nvl_chunk_size,
+                    "num_max_nvl_chunked_recv_tokens": nvl_buffer_size,
+                    "num_max_rdma_chunked_send_tokens": rdma_chunk_size,
+                    "num_max_rdma_chunked_recv_tokens": rdma_buffer_size,
+                }
+                config = deep_ep.Config(**config_kwargs)
+                tune_args = {"x": current_x, "handle": handle, "config": config}
+                t = bench(lambda: buffer.dispatch(**tune_args))[0]
+                if t < best_time:
+                    best_time, best_results = t, (
+                        num_sms,
+                        nvl_chunk_size,
+                        rdma_chunk_size,
+                        config_kwargs,
+                    )
+                if local_rank == 0:
+                    print(
+                        f"[tuning] SMs {num_sms}, NVL chunk {nvl_chunk_size}, RDMA chunk {rdma_chunk_size}: {rdma_send_bytes / 1e9 / t:.2f} GB/s (RDMA), {nvl_recv_bytes / 1e9 / t:.2f} GB/s (NVL) ",
+                        flush=True,
+                    )
+        if local_rank == 0:
+            print(
+                f'[tuning] Best dispatch ({"FP8" if isinstance(current_x, tuple) else "BF16"}): SMs {best_results[0]}, NVL chunk {best_results[1]}, RDMA chunk {best_results[2]}: {rdma_send_bytes / 1e9 / best_time:.2f} GB/s (RDMA), {nvl_recv_bytes / 1e9 / best_time:.2f} GB/s (NVL)',
+                flush=True,
+            )
+            print("", flush=True)
+            is_fp8 = isinstance(current_x, tuple)
+            if is_fp8:
+                output_data["normal_dispatch"] = deepcopy(best_results[3])
+
+        if isinstance(current_x, tuple):
+            # Gather FP8 the best config from rank 0
+            best_dispatch_results = torch.tensor(
+                [best_results[0], best_results[1], best_results[2]],
+                dtype=torch.int32,
+                device="cuda",
+            )
+            all_best_fp8_results_list = [
+                torch.zeros_like(best_dispatch_results)
+                for _ in range(torch.distributed.get_world_size())
+            ]
+            dist.all_gather(
+                all_best_fp8_results_list, best_dispatch_results, group=group
+            )
+            best_dispatch_results = all_best_fp8_results_list[0].tolist()
+    dispatch_config = deep_ep.Config(
+        best_dispatch_results[0],
+        best_dispatch_results[1],
+        nvl_buffer_size,
+        best_dispatch_results[2],
+        rdma_buffer_size,
+    )
+
+    dispatch_args = {
+        "x": x,
+        "num_tokens_per_rank": num_tokens_per_rank,
+        "num_tokens_per_rdma_rank": num_tokens_per_rdma_rank,
+        "is_token_in_rank": is_token_in_rank,
+        "num_tokens_per_expert": num_tokens_per_expert,
+        "config": dispatch_config if dispatch_config is not None else config,
+    }
+    recv_x, _, _, _, handle, _ = buffer.dispatch(**dispatch_args)
+
+    # Tune combine performance
+    best_time, best_results = 1e10, None
+    for nvl_chunk_size in range(1, 5, 1):
+        for rdma_chunk_size in range(8, 33, 4):
+            config_kwargs = {
+                "num_sms": num_sms,
+                "num_max_nvl_chunked_send_tokens": nvl_chunk_size,
+                "num_max_nvl_chunked_recv_tokens": nvl_buffer_size,
+                "num_max_rdma_chunked_send_tokens": rdma_chunk_size,
+                "num_max_rdma_chunked_recv_tokens": rdma_buffer_size,
+            }
+            config = deep_ep.Config(**config_kwargs)
+            tune_args = {"x": recv_x, "handle": handle, "config": config}
+            t = bench(lambda: buffer.combine(**tune_args))[0]
+            if local_rank == 0:
+                print(
+                    f"[tuning] SMs {num_sms}, NVL chunk {nvl_chunk_size}, RDMA chunk {rdma_chunk_size}: {combine_bf16_rdma_recv_bytes / 1e9 / t:.2f} GB/s (RDMA), {combine_bf16_nvl_send_bytes / 1e9 / t:.2f} GB/s (NVL) ",
+                    flush=True,
+                )
+                if t < best_time:
+                    best_time, best_results = t, (
+                        num_sms,
+                        nvl_chunk_size,
+                        rdma_chunk_size,
+                        config_kwargs,
+                    )
+
+    if local_rank == 0:
+        print(
+            f"[tuning] Best combine: SMs {best_results[0]}, NVL chunk {best_results[1]}, RDMA chunk {best_results[2]}: {combine_bf16_rdma_recv_bytes / 1e9 / best_time:.2f} GB/s (RDMA), {combine_bf16_nvl_send_bytes / 1e9 / best_time:.2f} GB/s (NVL)",
+            flush=True,
+        )
+        print("", flush=True)
+        output_data["normal_combine"] = deepcopy(best_results[3])
+
+    if rank == 0 and local_rank == 0:
+        _write_output(args, output_data)
+
+
+def _write_output(args, output_data):
+    text = json.dumps(output_data, indent=4)
+    output_path = args.output_path
+    print(f"Write to {output_path} with {text}")
+    Path(output_path).write_text(text)
+
+
+# noinspection PyUnboundLocalVariable
+def test_loop(local_rank: int, num_local_ranks: int, args):
+    num_nodes = args.nnodes
+    rank, num_ranks, group = init_dist(local_rank, num_local_ranks, args)
+
+    num_sms = args.num_sms
+    num_qps_per_rank = num_sms // 2
+
+    buffer = deep_ep.Buffer(
+        group,
+        int(1e9),
+        int(1e9),
+        low_latency_mode=False,
+        num_qps_per_rank=num_qps_per_rank,
+    )
+    assert num_local_ranks == 8 and num_ranks > 8
+    torch.manual_seed(rank)
+
+    for i in (num_sms,):
+        test_main(
+            i,
+            local_rank,
+            num_local_ranks,
+            num_ranks,
+            num_nodes,
+            rank,
+            buffer,
+            group,
+            args,
+        )
+        if local_rank == 0:
+            print("", flush=True)
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--num-sms", type=int, default=24)
+    parser.add_argument("--output-path", type=str, default="deepep_tuned.json")
+    parser.add_argument("--nnodes", type=int, default=1)
+    parser.add_argument("--node-rank", type=int, default=0)
+    parser.add_argument("--master-addr", type=str, default="127.0.0.1")
+    parser.add_argument("--master-port", type=int, default=8361)
+    args = parser.parse_args()
+    print(f"Start system with {args=}")
+
+    num_processes = 8
+    torch.multiprocessing.spawn(
+        test_loop, args=(num_processes, args), nprocs=num_processes
+    )