Refactor: stage hbg device args through the retained temporary buffer

[ChaoZheng109]

Fixes #2151

What

host_build_graph's bind path did a device_malloc + H2D + device_free for every host-side tensor argument on every run. tensormap_and_ringbuffer stopped doing that in #1198, which added a runner-scoped retained staging buffer that grows to the high-water packed size and is bump-sliced each run, so steady state converges to zero temporary device allocations.

Nothing about that mechanism was ever TRB-specific: HostApi has exposed get/set_retained_temp_buffer generically since #1198, and hbg already consumes three of DeviceRunnerBase's four per-pipeline-slot retained storages (Graph Definition blocks #1988, SM mirror #2013, ChipCallable/orch SO). This makes it consume the fourth. No platform change was needed.

How

One definition of the mechanism, and of the ledger. RetainedTempBump moves out of the two TRB runtime_maker.cpp files into src/common/utils/retained_temp_bump.h; the TensorLease ledger moves out of the three runtime.h files into src/common/utils/tensor_lease.h, with its release loop in utils/tensor_lease_release.h. The type is split from its release because both runtime.h files are included by AICore and AICPU translation units, which cannot see the host API.

RetainedTempBump::begin() takes a byte count instead of ChipStorageTaskArgs, which keeps that header free of task_interface types and leaves each caller's packing loop next to the staging loop it has to mirror. The packing rule, the 1024-byte slice alignment and the grow rule are unchanged, so TRB behaves exactly as before; diagnostics the two helpers used to log are now emitted by the callers, which have the tensor index and the logging backend.

After this, the only duplication left on this path is the packing function — duplicated on purpose, because each copy has to mirror its own runtime's staging predicate.

hbg's ledger takes TRB's shape. TensorPair becomes TensorLease and gains a TensorReleaseKind; validate releases through release_tensor_leases instead of device_freeing every recorded pointer, because a bump slice is not a separate allocation and must not be freed. Slices are recorded as BufferNoop; the buffer itself is freed once per Worker in DeviceRunnerBase::clear_temporary_buffer.

The two predicates are word for word identical. hbg's staging loop skips empty tensors exactly as TRB's does, and both packed_temp_bytes copies skip the same two cases. A tensor counted by one but not sliced by the other shifts every later slice off the offsets the buffer was sized from.

bind now clears the ledger on entry. A run whose validate never executes otherwise leaves its entries for the next bind. On the onboard native path a failed prepare still reaches validate_runtime_impl via cleanup_failed_prepare, so that path was already clean; the gap is a finalize whose attach_current_thread fails, which skips validation entirely. Stale entries were a leak before; with a reused buffer they name offsets the next bind re-slices, so validate would copy that run's bytes back to the earlier run's host pointer.

The grow lands inside the args bind-phase span. The one device allocation this phase can make is now attributed to it, so "steady state allocates nothing here" is a measurement rather than a definition — which matters because hbg-bind-phases is the tool this change is meant to be observed through.

Why it is safe

The retained slot is per pipeline_slot. A native run holds its slot from bind through validate, and a concurrent reservation is admitted only when it selects a distinct slot (device_runner_base.h, try_reserve_native_run), so no other run can re-slice a buffer whose slices are live. That is the same property hbg's Graph Definition blocks and SM mirror already rely on — hbg does not need TRB's "serial per runner" argument.

The H2D of a staged tensor still precedes its registration with the run's HostTensorAccessor, so a reused slice cannot expose the previous run's bytes to orchestration. (add() uses the caller's host buffer as the view when one is supplied, so slices install no platform mapping and cannot produce overlapping halHostRegister calls.)

One property worth knowing, now documented in both runtimes' RUNTIME_LOGIC.md: a pure OUT tensor is staged into a slice but never copied in and never zero-filled, so bytes a kernel does not write are whatever the slice last held. That was already true of a fresh device_malloc (the allocator pools device memory), but the residue is now this workload's own previous round rather than arbitrary — a kernel writing only part of its output now fails deterministically instead of randomly. device_memset exists for zero-filling pure outputs; neither runtime uses it, because it would cost a device operation per output per run.

Tests

• test_depth_two_slots_own_separate_resources asserted that neither hbg pipeline slot held a retained buffer. It now asserts both hold one and that the two are distinct — the regression barrier for this change. Verified passing onboard.
• New tests/ut/cpp/common/test_retained_temp_bump.cpp covers the mechanism against a fake HostApi: first allocation, reuse without allocation, grow (free old + malloc new), slice alignment/contiguity/disjointness, slice miss, a zero-byte run leaving the slot untouched, and a failed grow clearing the slot rather than leaving it naming the buffer it just freed.
• Existing test_trb_runtime_temp_buffer (both arches) stays green — that is the evidence the extraction did not change TRB.

Verification run

Suite	Result
ctest -LE requires_hardware	141/141 passed
pytest tests/ut/py	2242 passed, 24 skipped
a5sim / a2a3sim --runtime host_build_graph	21 passed / 20 passed 7 skipped
a5sim / a2a3sim --runtime tensormap_and_ringbuffer	50 passed / 55 passed 1 skipped
a2a3 onboard --runtime host_build_graph	46 passed, 1 skipped
a2a3 onboard --runtime tensormap_and_ringbuffer	94 passed, 18 failed — see below

The 18 onboard TRB failures are pre-existing and unrelated: all are L3/L4 cases whose forked chip worker exits with wait status 139 during init, before any bind. The identical 18 fail on an unmodified upstream/main build of the same tree, each passes when run on its own, and the set is byte-identical before and after this change.

Note on measurement

The two cases the hbg-bind-phases tooling instruments (dsv4 FLASH decode, qwen3-14b decode) both hand over device-resident buffers since #2041, so they take the is_device_memory() pass-through and never reach this code. There is therefore no perf number in this PR — the benefit lands on callers that still hand over host tensors, which is what the scene-test corpus and the external repos do. #1841 is the standing observation this sits under.

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📝 Walkthrough

Walkthrough

The host runtimes now stage caller tensors through retained per-slot temporary buffers. Shared tensor leases control copy-back and release behavior. Documentation and tests describe and validate buffer reuse, growth, alignment, failures, and slot ownership.

Changes

Retained tensor staging

Layer / File(s)	Summary
Shared lease and buffer contracts src/common/utils/*, src/common/host_build_graph/runtime.h, src/a2a3/.../runtime/runtime.h, src/a5/.../runtime/runtime.h	Adds shared TensorLease, release helpers, and RetainedTempBump; runtimes use the shared lease type.
Retained staging integration src/a2a3/runtime/host_build_graph/host/runtime_maker.cpp, src/a5/runtime/host_build_graph/host/runtime_maker.cpp, src/*/runtime/tensormap_and_ringbuffer/host/runtime_maker.cpp	Replaces per-tensor allocation with aligned retained-buffer slices. Bind and validate paths record leases, copy results, and centralize cleanup.
Runtime staging documentation docs/*, src/*/runtime/host_build_graph/docs/*, src/*/runtime/tensormap_and_ringbuffer/docs/*, src/common/platform/...	Documents retained-buffer reuse, H2D ordering, lease ownership, and pure-output behavior.
Staging and reuse validation tests/ut/cpp/common/test_retained_temp_bump.cpp, tests/st/a2a3/host_build_graph/run_stream_reuse/test_run_stream_reuse.py, tests/ut/cpp/CMakeLists.txt	Tests alignment, slicing, reuse, growth, allocation failure, zero-size runs, and distinct per-slot buffers.

Estimated code review effort: 4 (Complex) | ~45 minutes

Sequence Diagram(s)

sequenceDiagram
  participant RuntimeMaker
  participant RetainedTempBump
  participant HostApi
  participant HostTensorAccessor
  RuntimeMaker->>RetainedTempBump: begin required capacity
  RetainedTempBump->>HostApi: reuse or grow retained buffer
  RuntimeMaker->>RetainedTempBump: acquire tensor slice
  RuntimeMaker->>HostApi: copy readable tensor H2D
  RuntimeMaker->>HostTensorAccessor: register staged tensor
  RuntimeMaker->>HostApi: copy eligible results D2H

Loading

Merge Risk: 🟡 Moderate · up to bfebf

Oversized tensor arguments can reserve insufficient staging memory or use an invalid device slice, which can break runtime execution across both host runtimes. The incorrect pure-output guarantee should also be corrected before relying on the documented debugging behavior.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 34.69% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 49 functions across 16 files. (8 skipped:…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The implementation satisfies issue #2151: HBG now uses per-pipeline-slot retained bump-buffer slices, tracks release kinds, preserves H2D-before-registration ordering, applies the change to both archi…
Out of Scope Changes check	✅ Passed	The code, documentation, and tests are directly related to the retained-buffer staging refactor, lease-management changes, safety documentation, and regression coverage. No unrelated changes are evide…
Title check	✅ Passed	The title clearly and concisely describes the main change: staging HBG device arguments through the retained temporary buffer.
Description check	✅ Passed	The description directly explains the retained-buffer staging refactor, release-kind handling, safety properties, tests, and verification results.

Full details: Docstring Coverage

Explanation

Docstring coverage is 34.69% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 49 functions across 16 files. (8 skipped: 8 unsupported.)

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_{A rabbit finds a buffer wide,
And slices tensors side by side.
The slots keep staging close at hand,
Leases guide each cleanup strand.
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Actionable comments posted: 2

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Inline comments:
In `@src/a2a3/runtime/host_build_graph/docs/RUNTIME_LOGIC.md`:
- Around line 77-85: Update all four pure OUT residue discussions in
RUNTIME_LOGIC.md to qualify that prior-round bytes are guaranteed only for
unchanged retained slices; first allocation and post-growth
RetainedTempBump::begin() allocations may contain uninitialized allocator
residue because device_malloc does not initialize memory. Preserve the existing
explanation that pure OUT staging skips copy_to_device and that device_memset is
not used.

In `@src/common/utils/retained_temp_bump.h`:
- Line 41: Update RetainedTempBump::align_up() and acquire() to use
overflow-safe alignment and size accumulation: reject alignment arithmetic that
would exceed SIZE_MAX, reject aligned offsets greater than capacity_, and
compare requested bytes against capacity_ minus the aligned offset before
advancing the buffer. Add boundary tests covering sizes near SIZE_MAX and ensure
oversized requests cannot produce out-of-capacity pointers for HBG or TRB.

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📒 Files selected for processing (24)

• docs/dfx/hbg-bind-phases.md
• docs/dfx/host-trace.md
• docs/task-flow.md
• examples/workers/l3/child_memory/main.py
• src/a2a3/runtime/host_build_graph/docs/RUNTIME_LOGIC.md
• src/a2a3/runtime/host_build_graph/host/runtime_maker.cpp
• src/a2a3/runtime/tensormap_and_ringbuffer/docs/RUNTIME_LOGIC.md
• src/a2a3/runtime/tensormap_and_ringbuffer/host/runtime_maker.cpp
• src/a2a3/runtime/tensormap_and_ringbuffer/runtime/runtime.h
• src/a5/runtime/host_build_graph/docs/RUNTIME_LOGIC.md
• src/a5/runtime/host_build_graph/host/runtime_maker.cpp
• src/a5/runtime/tensormap_and_ringbuffer/docs/RUNTIME_LOGIC.md
• src/a5/runtime/tensormap_and_ringbuffer/host/runtime_maker.cpp
• src/a5/runtime/tensormap_and_ringbuffer/runtime/runtime.h
• src/common/host_build_graph/runtime.h
• src/common/host_build_graph/types.h
• src/common/platform/include/common/host_api.h
• src/common/platform/onboard/host/device_runner_base.h
• src/common/utils/retained_temp_bump.h
• src/common/utils/tensor_lease.h
• src/common/utils/tensor_lease_release.h
• tests/st/a2a3/host_build_graph/run_stream_reuse/test_run_stream_reuse.py
• tests/ut/cpp/CMakeLists.txt
• tests/ut/cpp/common/test_retained_temp_bump.cpp

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[ChaoZheng109]

Benchmark: a2a3 onboard, host_build_graph

The PR description says there is no perf number because the two cases the hbg-bind-phases tooling instruments are device-resident since #2041. That is still true of those two, but the scene-test corpus does still hand over host tensors, so it does exercise this path — here is that measurement.

Headline: 7 of 8 cases improve Host by 12–17%. The one case that provably cannot benefit does not move, which is the control that makes the rest credible.

Setup

base → head	a1aa7fdd → 505370c2
platform / runtime	a2a3 onboard, host_build_graph
command	./tools/benchmark_rounds.sh -n 100 -d 4 -r host_build_graph
device	4, pinned; both arms on the same die
order	base → head → head → base, each arm reported as the mean of its two runs
PTO-ISA	5a4f74cb on both arms

The alternating order is deliberate. A naive base then head sequence gives the second arm a systematically warmer page cache and device; running each arm in both positions cancels it.

Independence of the two builds — verified, not assumed

A baseline worktree that silently shares the main tree's build products would produce a table that looks entirely normal and means nothing. build-dir in pyproject.toml is build/{wheel_tag}, i.e. relative to the CWD at build time, so installing the worktree from the main tree's directory stamps the worktree's source path into the main tree's CMake cache and both arms end up on one binary. The baseline was therefore installed from inside the worktree with an absolute --config-settings=build-dir=..., and each of these was checked before running:

• libhost_runtime.so differs by md5 and by inode between the arms;
• the baseline binary does not contain the Retained temp buffer slice miss for tensor string and the head binary does — i.e. each arm really is its own side of the diff;
• both arms' build/lib/pto_isa_build.json report actual == required == 5a4f74cb;
• SIMPLER_DFX=1, SIMPLER_ORCH_PROFILING=0, SIMPLER_SCHED_PROFILING=0, SIMPLER_TENSORMAP_PROFILING=0 on both — identical instrumentation.

Host (us, mean of two runs)

Example	base	HEAD	Δ	Change
alternating_matmul_add (Case1)	32860	27503	−5358	−16.31%
benchmark_bgemm (Case0)	15212	13413	−1799	−11.83%
paged_attention_unroll (Case1)	32440	28583	−3857	−11.89%
paged_attention_unroll (Case2)	10385	8631	−1754	−16.89%
paged_attention_unroll_manual_scope (Case1)	32674	28088	−4586	−14.03%
paged_attention_unroll_manual_scope (Case2)	10394	8999	−1395	−13.42%
batch_paged_attention (Case1)	35155	30783	−4372	−12.44%
qwen3_14b_decode (Batch16Seq3500)	38140	38067	−73	−0.19%

Within-arm spread (max abs(r1−r2)/mean over all cases and both arms) is 5.05%, so the 12–17% improvements sit 2–3× above the noise floor and reproduce in both orderings.

The control

qwen3_14b_decode keeps every parameter device-resident since #2041, so it takes the is_device_memory() pass-through and never reaches the staging loop this PR changes. It moves −0.19% on Host and −0.25% on Device — both inside noise. The case that should not change did not, which is the strongest single argument that the other seven are measuring the change rather than the environment.

Device (us, mean of two runs) — this does move, and it is not a confound

Example	base	HEAD	Δ	Change
paged_attention_unroll_manual_scope (Case2)	679.4	597.9	−81.5	−11.99%
paged_attention_unroll (Case2)	677.8	601.0	−76.8	−11.33%
paged_attention_unroll (Case1)	1275.1	1201.4	−73.8	−5.78%
paged_attention_unroll_manual_scope (Case1)	1275.8	1203.0	−72.8	−5.70%
batch_paged_attention (Case1)	2833.8	2720.3	−113.5	−4.00%
benchmark_bgemm (Case0)	729.6	719.1	−10.5	−1.44%
qwen3_14b_decode	37552.8	37457.6	−95.3	−0.25%
alternating_matmul_add (Case1)	856.8	905.2	+48.4	+5.65%

Device noise floor is 0.63%, so most of these are real. That deserves an explanation, because the change touches no device code.

It is a data-layout effect. Staged tensors used to be N independent rtMalloc results at scattered addresses; they are now 1024-byte-aligned adjacent slices of one contiguous buffer. Device time therefore shifts with how each kernel's access pattern interacts with the new locality — which is exactly why the sign is not uniform. Instrumentation is ruled out: the compile flags above are identical on both arms.

alternating_matmul_add is the one regression, at +48 us of device time against −5358 us of host time on the same case. Worth knowing about; not, on these numbers, worth blocking on.

What this does and does not claim

• The benefit is on the host bind path and is proportional to the number of staged tensors, not their size — what disappears is one rtMalloc + rtFree pair per host tensor per run.
• Callers whose tensors are already device-resident get nothing, as qwen3_14b_decode shows.
• One device, one session, one host. The absolute numbers are not portable; the deltas reproduced across four arms on a pinned die.

[zhusy54]

Review comments are attached to the corresponding source lines. The main blocking issue is the alignment contract mismatch; the other comments cover the missing failure-path regression, obsolete lease states, readability, and documentation consistency.

[poursoul]

检视意见

结论:approve。 未发现正确性缺陷;slot 独占性的安全论证经独立核验成立。下面两条 should-fix 都不阻塞合并。

Stated goal 与 Real goal

一致。改动确实只做了三件事 —— 把机制上移到 src/common/utils/、让 hbg 接入、统一台账(ledger),TRB 一侧是纯搬迁。没有夹带范围外改动。

我独立核验过的点

• slot 独占性是真的,hbg 确实不需要 TRB 那套"每个 runner 串行"的论证。 try_reserve_native_run 在 reservation.pipeline_slot == pipeline_slot 处直接拒绝(device_runner_base.cpp:2010),allow_prepared_successor 也绕不过这一条;reservation 在 validate 之后才释放(onboard/host/c_api_shared.cpp:734)。所以切片存活期内不可能被另一个 run 重新切分。
• 确实不需要平台改动,也不会漏释放。 两个 backend 早就各自持有槽位并在 finalize 释放一次 —— onboard/host/device_runner_base.cpp:279-283、sim/host/device_runner_base.cpp:515-519。
• arch 对称性: a2a3 与 a5 的 diff 除上下文行外逐字相同,两个 runtime 都是。
• 抽出的 acquire() 相比 TRB 原版有两处严格改进,且都被新单测钉住了:边界检查改写成减法(于是溢出的 nbytes() 落成一次 miss,而不是交出越过缓冲末尾的指针);grow 失败时清空槽位,而不是让它继续指着刚被 free 掉的缓冲。
• CI 全绿,含两个 onboard arch —— 这同时也证明了 AICore/AICPU 的 translation unit 能解析新的 utils/tensor_lease.h。

Should fix

1. 零字节 tensor 这一条对 hbg 是行为变更,不只是 predicate 对齐。

PR 描述把新增的 if (size == 0) 跳过写成 "hbg's staging loop skips empty tensors exactly as TRB's does"。但在这次改动之前,一个零字节的非 child、非纯 OUT tensor 会让 hbg 的 bind 直接失败:HostTensorAccessor::add 对 size == 0 返回 false(src/common/host_build_graph/host/host_tensor_access.cpp:72),于是循环落到 LOG_ERROR("host-orch: no host view for tensor %d") 并返回 PTO_RUNTIME_ERR_INTERNAL。改动之后这个 tensor 被接受,以 buffer.addr = 0 透传。

方向是对的 —— TRB 一直就是这个语义,已经在线上跑 —— 但这是一个藏在重构里的修复:

• 只读 PR 描述的人看不出 hbg 从拒绝这类输入变成了接受;
• 没有测试。按 .claude/rules/discipline.md §3,行为修复应当留下回归屏障。

建议在 PR 描述和 hbg 的 RUNTIME_LOGIC.md 里明确写出这一条,并补一个零字节 tensor 的用例。

2. packed_temp_bytes 复制了四份,而它恰好就是 PR 自己声明"绝不能分叉"的那个 predicate。

四个副本(hbg/TRB × a2a3/a5)函数体逐字节相同,只有文档注释不同。而它们上方的注释已经把失效模式说得很准 —— "a tensor counted here but not sliced there ... shifts every later slice off the offsets this size was computed from" —— 也就是一类静默的偏移错位,唯一的防线是人的自觉。

把它排除在 retained_temp_bump.h 之外的理由(保持该 header 不依赖 task_interface 类型)是偏好而非约束:ChipStorageTaskArgs 就定义在共享的 src/common/task_interface/task_args.h:197,两个 runtime、两个 arch 用的是同一个类型。既然这个 PR 本身就是在做收敛,建议把 plan/size 这一步也一起收进来 —— RetainedTempBump::plan(orch_args),或者单独一个 utils/staged_tensor_plan.h —— 让这个 predicate 只存在一份。这正是 PR 想守住的那个不变量。

Consider

3. TensorReleaseKind 三个取值里有两个没有生产者 —— 撤回,与 @zhusy54 在 src/common/utils/tensor_lease.h:30 的意见重复,以那条为准。

我提交时没有先读完已有的 inline 评审,这条与 @zhusy54 已经提出的完全撞车:同样指出 ExternalNoop 零生产者、Free 因唯一调用点永远传 &bump 而不可达,连"把 bump 参数改成非空引用"的建议也是同一个。请按那条线程讨论,不要在两处分头回复。

下面第 4 条与那条线程有部分重叠(它提到"the new release helper only counts no-ops"),仅"四份逐字相同的包装函数"这一点是额外的。

4. release_run_tensor_leases 同样是四份逐字相同的 static 包装,唯一的职责是打一行日志。 release_tensor_leases 已经返回 counts 了,两个调用点直接打日志即可,包装可以去掉。

5. hbg 原来的 LOG_INFO("Freed %d device allocations") 变成了共享 release 内部的 LOG_DEBUG。 一条一直出现在 onboard 日志里的行在默认 verbosity 下消失了 —— 如果有人靠它排查释放数量,值得在 PR 描述里提一句。

pto-isa pin

ℹ️ pto_isa.pin 固定在 5a4f74cbf627d4aac2e0ce10d5e0d8b118343265。本 PR 未改动任何 pto-isa header 引用,所以这里只是例行提醒:确认该 commit 仍然够用即可,不涉及 bump 或重建 onboard host_runtime.so。

体量

总 churn 1144 行,超过通常的 1000 行拆分阈值 —— 但其中 Core 占 763 行,而这 763 里约 200 行是纯搬迁,整体是同一个关注点镜像了四份。这个 PR 我不建议拆。

[ChaoZheng109]

@zhusy54 All seven addressed in this branch; each inline thread has its own reply and is resolved. Summary against your framing:

The blocking one — alignment contract. You were right on both halves: aligning the slice offset cannot repair a misaligned base, and my test double's aligned_alloc was hiding the mismatch. Rather than change the sim allocator or narrow the contract, RetainedTempBump now makes the guarantee itself — begin() over-allocates by kAlignment - 1 and aligns inside the allocation, keeping the raw pointer in the slot for device_free. Both test doubles (mine and TRB's, which used posix_memalign) now allocate with plain std::malloc, so a base the bump failed to align is visible rather than masked.

The missing regression. Added, and my first assessment of its cost was wrong: I thought an hbg bind test needed an orchestration .so. It does not — dlopen is in register_callable_impl, and bind takes the resolved entry points as a parameter, so the test supplies its own two function pointers. test_hbg_bind_ledger.cpp binds one Runtime twice with no validate between and asserts both the ledger contents and that the earlier run's host buffer is untouched. Verified to fail without the clear().

The obsolete lease states. Confirmed and extended: ExternalNoop has no producer anywhere and never had one since #1198 introduced it. Filed as #2196 with your suggested shape rather than done here, since it touches both runtimes' shared ledger and TRB's staging function while this change is scoped to hbg's staging path.

Readability and documentation. All fixed, plus three more of the same class found by grepping: two tensor.h comments naming init_runtime_impl, and a TRB TIMING: total_init_runtime_impl log label.

One thing I did not do and want to flag rather than bury: hbg still has only one of TRB's two defenses. TRB clears the ledger at bind entry and releases it from an RAII guard on every early return; hbg has just the clear. Its ten early returns after staging begins are covered by callers instead — every bind-failure path reaches validate_runtime_impl with a non-zero execution_rc, which skips copy-back and releases. That works, but it is an external argument where TRB's is internal. Happy to add the guard here if you'd rather have the parity.