sgl-project/sglang · error · ValueError

expert-pack stats flush interval cannot be negative

Error message

expert-pack stats flush interval cannot be negative

What it means

ExpertPackStore._initialize_runtime_state rejects stats_flush_interval < 0. The interval controls how often cache statistics are flushed; negative intervals are meaningless (and would be treated as truthy/always by some code paths), so they are rejected at construction.

Source

Thrown at python/sglang/srt/layers/moe/expert_pack.py:188

) -> None:
    store.cache_vram_mib = int(cache_vram_mib)
    store.cache_vram_reserve_mib = int(cache_vram_reserve_mib)
    store.kernel_backend = "custom"
    store.stage_slot_count = int(stage_slots)
    store.read_splits = int(read_splits)
    store.direct_io = bool(direct_io)
    store.stats_flush_interval = int(stats_flush_interval)
    if (
        store.cache_vram_mib <= 0
        or store.cache_vram_reserve_mib <= 0
        or store.stage_slot_count <= 0
        or store.read_splits <= 0
    ):
        raise ValueError(
            "expert cache and staging budgets, and read splits, must be positive"
        )
    if store.stats_flush_interval < 0:
        raise ValueError("expert-pack stats flush interval cannot be negative")
    if store.direct_io and not hasattr(os, "O_DIRECT"):
        raise ValueError("expert-pack direct I/O is unavailable on this platform")
    open_flags = os.O_RDONLY | (os.O_DIRECT if store.direct_io else 0)
    store._fd = os.open(store.path, open_flags)
    store._lock = threading.RLock()
    store._cache = None
    store._cache_slots = []
    store._key_to_slot = {}
    store._key_frequency = {}
    store._lru = OrderedDict()
    store._staging = []
    store._stage_events = []
    store._stage_cursor = 0
    store._transfer_stream = None
    store._read_executor = None
    store._active_keys = set()
    store._route_calls_by_layer = [0] * store.header.num_layers
    store._route_tokens_by_layer = [0] * store.header.num_layers

View on GitHub (pinned to 0132848349)

Solutions

1. Use 0 to disable periodic stats flushing instead of a negative value
2. Set a positive interval such as 5.0 seconds if stats are wanted
3. Audit config arithmetic that produces the interval and clamp at 0

Example fix

# before
store = ExpertPackStore(p, stats_flush_interval=-1)  # tried to disable

# after
store = ExpertPackStore(p, stats_flush_interval=0)  # disabled

stats_flush_interval = max(0.0, float(stats_flush_interval))

When it happens

Trigger: Constructing ExpertPackStore with stats_flush_interval=-1 or a computed negative value, e.g. from subtracting overheads or parsing a signed CLI/env value.

Common situations: Using -1 as an 'unlimited/disabled' sentinel (0 is the correct value for disabled here); arithmetic that computes a negative interval from timing config; misparsed config files.

Related errors

• expert cache and staging budgets, and read splits, must be p
• expert-pack direct I/O is unavailable on this platform
• Removed server argument(s): {replacements}
• expert-pack header coverage is inconsistent
• expert-pack is not identity triplet layout

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/7fa2168d0d034082. Report an issue: GitHub.