CP shared-KV performance debugging depends on seeing when the runtime leaves the intended TAI, IPC, prefetch, or current-reuse paths. This change makes those misses visible through standardized warning markers while keeping per-reason log limits to avoid per-layer log floods.\n\nThe warnings intentionally distinguish fallback from fail-fast: unsupported correctness-sensitive states still raise, while performance-path misses emit [CP_SHARED_KV_FALLBACK] with the concrete reason.\n\nConstraint: Production ETE debugging needs visible fallback evidence without enabling heavy debug mode, which can itself disable fast paths.\nRejected: Rely only on optional MLA prefetch debug logs | they are env-gated, layer-limited, and miss non-prefetch TAI/IPC/current-reuse fallbacks.\nRejected: Log every per-layer event without limits | would drown useful transfer/cache diagnostics under steady-state traffic.\nConfidence: high\nScope-risk: moderate\nDirective: Do not remove these fallback warnings unless an equivalent low-noise observability path exists for every fast-path miss.\nTested: local py_compile for touched files; local git diff --check for touched files; remote g0034 py_compile and pytest for test_nsa_cp_utils.py, test_cp_shared_kv_layout.py, test_cp_shared_kv_runtime.py passed before commit (156 passed, 5 warnings, 2 subtests passed).\nNot-tested: full ETE serving traffic after warning additions.
Unit Tests
Component-level tests that do not launch a server or load model weights. Tests can use CPU or GPU — the key criterion is no server process.
Quick Start
- Find the source file under
python/sglang/srt/. - Create the corresponding test here, mirroring the source tree:
srt/mem_cache/radix_cache.py → unit/mem_cache/test_radix_cache.py srt/sampling/sampling_params.py → unit/sampling/test_sampling_params.py - Register for CI at the top of the file (after imports, before test classes):
from sglang.test.ci.ci_register import register_cpu_ci register_cpu_ci(est_time=5, suite="stage-a-test-cpu") # or: register_cuda_ci(est_time=10, suite="stage-b-test-1-gpu-small") - Run locally:
pytest test/registered/unit/ -v # all unit tests pytest test/registered/unit/mem_cache/ -v # one module - Run with coverage:
# summary pytest test/registered/unit/ --cov --cov-config=.coveragerc -v # PR incremental check (require ≥60% on changed lines) pytest test/registered/unit/ --cov --cov-config=.coveragerc --cov-report=xml diff-cover coverage.xml --compare-branch=origin/main --fail-under=60
Example
"""Unit tests for <module> — no server, no model loading."""
from sglang.test.ci.ci_register import register_cpu_ci
register_cpu_ci(est_time=5, suite="stage-a-test-cpu")
import unittest
from sglang.srt.<module> import TargetClass
from sglang.test.test_utils import CustomTestCase
class TestTargetClass(CustomTestCase):
def test_basic_behavior(self):
obj = TargetClass(...)
self.assertEqual(obj.method(), expected)
if __name__ == "__main__":
unittest.main()
Rules
- No
popen_launch_server()orEngine(...). - No model weight loading.
- Use
CustomTestCase(fromsglang.test.test_utils, adds CI retry). - Use
unittest.mockfor dependencies that are expensive to construct.