In CP=8 + NSA-shared-KV + HiCache disagg-prefill, cache-hit prefill produced incoherent decode output. Cold prefill on CP was correct; pure CP without HiCache was correct. The bug lived at the HiCache load_cp / device-alloc interface. Root cause: cache_controller.load_cp called the plain mem_pool_device_allocator.alloc(logical_len), which returns logical pages with no CP owner-pattern preservation. Cold prefill instead uses alloc_extend_compute_owner with a zigzag owner pattern from build_in_seq_page_compute_owners. The saved CpHiCacheNodeMetadata.owned_positions records WHICH POSITIONS in the write-time alloc were owned by this rank. At load time, those same positions are applied to a new alloc whose per-position owner pattern is arbitrary -- each rank loads its host bytes into physical slots whose corresponding logical page is owned by a DIFFERENT rank. Attention's materialize_shared_token_kv_buffer reads from the owner's physical slot, which was never loaded. Result: garbage. Fix: - CpHiCacheNodeMetadata gains two required fields: page_owners (int8 per logical page, identical on all CP ranks) and page_size. __post_init__ validates; split() bisects page_owners by page index with a page-alignment check. - _write_cp derives page_owners from device_indices (page-first slot of each page -> logical page id -> layout.owner_for_logical_pages) and stores in both metadata-construction sites (zero-owned and normal). - New CPSharedPagedTokenToKVPoolAllocator.alloc_pages_with_owners() reuses _select_compute_owner_pages (with its tai-kernel fast path) and returns page-contiguous token locs whose per-page owner sequence equals the input. - load_cp now concats page_owners across nodes_to_load and calls alloc_pages_with_owners. On None (lane exhausted) the caller hits the retry-with-eviction path; further failure returns None and degrades to cache miss. No silent fallback to plain alloc -- that recreated the bug. - load_back retry path now calls _evict_for_compute_owner_lanes (module-top import) instead of plain evict(); this targets the deficit lane and gives the next alloc attempt a chance to satisfy it. - envs import moved to module top in cache_controller.py per code-review feedback. Removed an over-defensive owned_check.all().item() in load_cp that would have re-introduced the host-sync anti-pattern 97a9f850c removed -- the invariant is already guaranteed by alloc_pages_with_owners. Tests: 40 existing CpHiCacheNodeMetadata constructions migrated to pass the new required fields. 9 new metadata tests (validators + split page-alignment). 10 new allocator tests in test_alloc_pages_with_owners.py covering input-order preservation, lane exhaustion, release_pages fallback, debug-mode invariant. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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.