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[BugFix] fix(hicache): fix two slot-reuse races in DecodeKVCacheOffloadManager (#24226)

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This commit is contained in:
Kevin Flansburg
2026-05-20 18:20:19 -07:00
committed by GitHub
parent c4a7d12092
commit 643d44d699
3 changed files with 291 additions and 21 deletions
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test/registered/disaggregation/test_disaggregation_decode_offload.py
-1
View File
@@ -21,7 +21,6 @@ register_cuda_ci(
est_time=600,
stage="base-b",
runner_config="2-gpu-large",
disabled="Temporarily disable the flaky test.",
)
test/registered/disaggregation/test_specv2_kvcache_offloading.py
+235
View File
@@ -15,6 +15,7 @@ import torch
from sglang.srt.disaggregation.decode_kvcache_offload_manager import (
DecodeKVCacheOffloadManager,
)
from sglang.srt.disaggregation.kv_events import OffloadedState
from sglang.test.ci.ci_register import register_cuda_ci
register_cuda_ci(est_time=8, stage="base-b", runner_config="1-gpu-small")
@@ -77,10 +78,18 @@ def _make_manager(pool_size: int, page_size: int = 1):
manager.page_size = page_size
manager.tree_cache = tree_cache
manager.offloaded_state = {}
manager.ongoing_offload = {}
manager.ongoing_backup = {}
manager.offload_inflight = {}
return manager, freed_indices
class _FinishedEvent:
def synchronize(self):
pass
class TestReleaseFinishedReq(unittest.TestCase):
"""Tests for _release_finished_req overallocation cleanup."""
@@ -176,6 +185,232 @@ class TestReleaseFinishedReq(unittest.TestCase):
self.assertEqual(manager.tree_cache.protected_size_, 5)
def test_release_finished_req_frees_prefill_when_state_present(self):
"""
When offloaded_state[rid].prefill_len > 0, _release_finished_req must
free the prefill-aligned slots in addition to the committed range.
This is the consolidated free path that replaces the eager free that
previously happened in offload_kv_cache (which raced with concurrent
admission and produced cross-pollinated KV reads).
"""
manager, freed = _make_manager(pool_size=32)
rid = "req-prefill-present"
req = _make_mock_req(
req_pool_idx=0,
kv_committed_len=20,
kv_allocated_len=20,
rid=rid,
)
manager.offloaded_state[rid] = OffloadedState(
prefill_len=8, inc_len=0, last_hash=None
)
manager._release_finished_req(req, start_offset=8)
# Two frees in order: prefill [0:8] then committed [8:20].
self.assertEqual(len(freed), 2)
expected_prefill = torch.arange(0, 8, dtype=torch.int64)
expected_committed = torch.arange(8, 20, dtype=torch.int64)
self.assertTrue(torch.equal(freed[0], expected_prefill))
self.assertTrue(torch.equal(freed[1], expected_committed))
# State entry is removed at the end of _release_finished_req.
self.assertNotIn(rid, manager.offloaded_state)
def test_release_finished_req_skips_prefill_free_when_prefill_len_zero(self):
"""
When state exists but prefill_len == 0 (request shorter than page_size,
so no prefill chunk was ever offloaded), no prefill-aligned free is
emitted.
"""
manager, freed = _make_manager(pool_size=32)
rid = "req-prefill-zero"
req = _make_mock_req(
req_pool_idx=0,
kv_committed_len=10,
kv_allocated_len=10,
rid=rid,
)
manager.offloaded_state[rid] = OffloadedState(
prefill_len=0, inc_len=0, last_hash=None
)
manager._release_finished_req(req, start_offset=0)
# Only the committed range [0:10] is freed.
self.assertEqual(len(freed), 1)
expected_committed = torch.arange(0, 10, dtype=torch.int64)
self.assertTrue(torch.equal(freed[0], expected_committed))
def test_finalize_release_creates_state_so_prefill_is_freed(self):
"""
finalize_release_on_finish handles the case where no incremental
offload ever ran (offloaded_state is empty). It must materialize an
OffloadedState with the correct prefill_len so that the consolidated
free site in _release_finished_req can locate and free those slots.
"""
page_size = 4
manager, freed = _make_manager(pool_size=32, page_size=page_size)
rid = "req-finalize-no-state"
req = _make_mock_req(
req_pool_idx=0,
kv_committed_len=13,
kv_allocated_len=13,
rid=rid,
)
# 12 input tokens => prefill_len = 12 // 4 * 4 = 12
req.origin_input_ids = list(range(12))
manager.finalize_release_on_finish(req)
# finalize creates state, then _release_finished_req frees:
# prefill [0:12] then committed [12:13].
self.assertEqual(len(freed), 2)
expected_prefill = torch.arange(0, 12, dtype=torch.int64)
expected_committed = torch.arange(12, 13, dtype=torch.int64)
self.assertTrue(torch.equal(freed[0], expected_prefill))
self.assertTrue(torch.equal(freed[1], expected_committed))
# State is deleted by _release_finished_req on the way out.
self.assertNotIn(rid, manager.offloaded_state)
def test_unfinished_offload_ack_does_not_free_incremental_slots(self):
manager, freed = _make_manager(pool_size=32)
req = _make_mock_req(
req_pool_idx=0, kv_committed_len=20, kv_allocated_len=20, rid=1
)
req.finished.return_value = False
manager.offloaded_state[req.rid] = OffloadedState(
prefill_len=4, inc_len=4, last_hash=None
)
manager.offload_inflight[req.rid] = 1
manager.ongoing_offload[7] = (
req,
torch.arange(4, 8, dtype=torch.int64),
[10, 11, 12, 13],
0.0,
4,
8,
)
manager.cache_controller = MagicMock()
manager.cache_controller.ack_write_queue = [(None, _FinishedEvent(), [7])]
manager._trigger_backup = MagicMock(return_value="last_hash")
manager._check_offload_progress(1)
self.assertEqual(freed, [])
manager.req_to_token_pool.free.assert_not_called()
self.assertNotIn(req.rid, manager.offload_inflight)
def test_offload_kv_cache_tracks_inflight_write_until_ack(self):
manager, freed = _make_manager(pool_size=32, page_size=4)
manager.cache_controller = MagicMock()
manager.cache_controller.get_hash_str = MagicMock(return_value="prefill_hash")
manager.cache_controller.write = MagicMock(
return_value=torch.arange(4, 8, dtype=torch.int64)
)
manager.decode_host_mem_pool = MagicMock()
manager.request_counter = 0
manager.offload_stride = 4
req = _make_mock_req(
req_pool_idx=0, kv_committed_len=20, kv_allocated_len=20, rid=5
)
req.origin_input_ids = [0, 1, 2, 3]
req.output_ids = [4, 5, 6, 7, 8]
req.finished.return_value = False
did_offload = manager.offload_kv_cache(req)
self.assertTrue(did_offload)
self.assertEqual(manager.offload_inflight[req.rid], 1)
self.assertEqual(manager.offloaded_state[req.rid].inc_len, 4)
manager.cache_controller.write.assert_called_once()
manager.cache_controller.ack_write_queue = [(None, _FinishedEvent(), [1])]
manager._trigger_backup = MagicMock(return_value="last_hash")
manager._check_offload_progress(1)
self.assertEqual(freed, [])
self.assertNotIn(req.rid, manager.offload_inflight)
def test_finalize_release_defers_while_offload_is_in_flight(self):
manager, freed = _make_manager(pool_size=32)
req = _make_mock_req(
req_pool_idx=0, kv_committed_len=20, kv_allocated_len=20, rid=2
)
manager.offloaded_state[req.rid] = OffloadedState(
prefill_len=4, inc_len=8, last_hash=None
)
manager.offload_inflight[req.rid] = 1
manager.finalize_release_on_finish(req)
self.assertEqual(freed, [])
manager.req_to_token_pool.free.assert_not_called()
self.assertIn(req.rid, manager.offloaded_state)
def test_finished_offload_ack_waits_for_other_inflight_writes(self):
manager, freed = _make_manager(pool_size=32)
req = _make_mock_req(
req_pool_idx=0, kv_committed_len=20, kv_allocated_len=20, rid=3
)
req.finished.return_value = True
manager.offloaded_state[req.rid] = OffloadedState(
prefill_len=4, inc_len=8, last_hash=None
)
manager.offload_inflight[req.rid] = 2
manager.ongoing_offload[8] = (
req,
torch.arange(4, 8, dtype=torch.int64),
[10, 11, 12, 13],
0.0,
4,
8,
)
manager.cache_controller = MagicMock()
manager.cache_controller.ack_write_queue = [(None, _FinishedEvent(), [8])]
manager._trigger_backup = MagicMock(return_value="last_hash")
manager._check_offload_progress(1)
self.assertEqual(freed, [])
manager.req_to_token_pool.free.assert_not_called()
self.assertEqual(manager.offload_inflight[req.rid], 1)
def test_finished_request_releases_all_committed_slots_after_last_offload_ack(
self,
):
manager, freed = _make_manager(pool_size=32)
req = _make_mock_req(
req_pool_idx=0, kv_committed_len=20, kv_allocated_len=20, rid=4
)
req.finished.return_value = True
manager.offloaded_state[req.rid] = OffloadedState(
prefill_len=4, inc_len=8, last_hash=None
)
manager.offload_inflight[req.rid] = 1
manager.ongoing_offload[9] = (
req,
torch.arange(8, 12, dtype=torch.int64),
[14, 15, 16, 17],
0.0,
8,
12,
)
manager.cache_controller = MagicMock()
manager.cache_controller.ack_write_queue = [(None, _FinishedEvent(), [9])]
manager._trigger_backup = MagicMock(return_value="last_hash")
manager._check_offload_progress(1)
self.assertEqual(len(freed), 2)
self.assertTrue(torch.equal(freed[0], torch.arange(0, 4, dtype=torch.int64)))
self.assertTrue(torch.equal(freed[1], torch.arange(4, 20, dtype=torch.int64)))
manager.req_to_token_pool.free.assert_called_once_with(req)
self.assertNotIn(req.rid, manager.offloaded_state)
self.assertNotIn(req.rid, manager.offload_inflight)
if __name__ == "__main__":
unittest.main()