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[Fix] Select custom all-reduce v2 by topology capability (#35061)

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Co-authored-by: xingyuliu <xingyuliu@fb.com>
This commit is contained in:
Xingyu Liu
2026-08-18 10:30:10 -07:00
committed by GitHub
co-authored by xingyuliu
parent 480033def0
commit 7dcaf11987
8 changed files with 268 additions and 236 deletions
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test/registered/unit/server_args/test_mnnvl_auto_inference.py
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"""Unit tests for the MNNVL auto-inference gate.
The TP8 best-throughput launch used to require exporting
``SGLANG_ENABLE_CUSTOM_ALL_REDUCE_V2_MULTINODE=1`` by hand. It is now
capability-inferred; these cases pin the negative-branch contracts so a
refactor cannot silently turn the predicate into always-true (engaging fabric
paths on non-fabric clusters) or drop the explicit-off override.
"""
import unittest
from types import SimpleNamespace
from unittest.mock import patch
from sglang.srt.environ import envs
from sglang.srt.server_args import ServerArgs
from sglang.test.ci.ci_register import register_cpu_ci
from sglang.test.test_utils import CustomTestCase
register_cpu_ci(est_time=5, suite="base-a-test-cpu")
_HANDLE = ServerArgs._handle_custom_all_reduce_v2_multinode
def _cleared(*fields):
"""Context helper: run with the given env fields unset, restore after."""
import contextlib
import os
@contextlib.contextmanager
def ctx():
backup = {f.name: os.environ.pop(f.name, None) for f in fields}
try:
yield
finally:
for name, val in backup.items():
if val is None:
os.environ.pop(name, None)
else:
os.environ[name] = val
return ctx()
class TestCaV2MultinodeAuto(CustomTestCase):
def test_fabric_multinode_auto_enables(self):
"""GB200/GB300 + nnodes>1 + unset opt-in -> multinode mode on, v2 kept."""
with _cleared(
envs.SGLANG_ENABLE_CUSTOM_ALL_REDUCE_V2_MULTINODE,
envs.SGLANG_OPT_USE_CUSTOM_ALL_REDUCE_V2,
), patch("sglang.srt.server_args.is_mnnvl_fabric_device", return_value=True):
_HANDLE(SimpleNamespace(nnodes=2, tp_size=8))
self.assertTrue(envs.SGLANG_ENABLE_CUSTOM_ALL_REDUCE_V2_MULTINODE.get())
self.assertTrue(envs.SGLANG_OPT_USE_CUSTOM_ALL_REDUCE_V2.get())
def test_non_fabric_multinode_still_disables_v2(self):
"""Non-fabric multi-node keeps the legacy force-disable (the predicate
must not degrade to always-true)."""
with _cleared(
envs.SGLANG_ENABLE_CUSTOM_ALL_REDUCE_V2_MULTINODE,
envs.SGLANG_OPT_USE_CUSTOM_ALL_REDUCE_V2,
), patch("sglang.srt.server_args.is_mnnvl_fabric_device", return_value=False):
_HANDLE(SimpleNamespace(nnodes=2, tp_size=8))
self.assertFalse(envs.SGLANG_ENABLE_CUSTOM_ALL_REDUCE_V2_MULTINODE.get())
self.assertFalse(envs.SGLANG_OPT_USE_CUSTOM_ALL_REDUCE_V2.get())
def test_explicit_off_wins_over_fabric(self):
"""SGLANG_ENABLE_CUSTOM_ALL_REDUCE_V2_MULTINODE=0 on a fabric device
must still force-disable v2 (explicit off beats auto-detection)."""
with _cleared(envs.SGLANG_OPT_USE_CUSTOM_ALL_REDUCE_V2), patch(
"sglang.srt.server_args.is_mnnvl_fabric_device", return_value=True
), envs.SGLANG_ENABLE_CUSTOM_ALL_REDUCE_V2_MULTINODE.override("0"):
_HANDLE(SimpleNamespace(nnodes=2, tp_size=8))
self.assertFalse(envs.SGLANG_ENABLE_CUSTOM_ALL_REDUCE_V2_MULTINODE.get())
self.assertFalse(envs.SGLANG_OPT_USE_CUSTOM_ALL_REDUCE_V2.get())
def test_tp16_not_auto_opted_in(self):
"""CustomAllReduceV2 supports world sizes 2..8 only; a TP16 fabric
launch must not auto-set the multinode opt-in (it would log
'enabling' and then silently fall back downstream)."""
with _cleared(
envs.SGLANG_ENABLE_CUSTOM_ALL_REDUCE_V2_MULTINODE,
envs.SGLANG_OPT_USE_CUSTOM_ALL_REDUCE_V2,
), patch("sglang.srt.server_args.is_mnnvl_fabric_device", return_value=True):
_HANDLE(SimpleNamespace(nnodes=2, tp_size=16))
self.assertFalse(envs.SGLANG_ENABLE_CUSTOM_ALL_REDUCE_V2_MULTINODE.is_set())
if __name__ == "__main__":
unittest.main()