Name L3 by its topology position, not by the processor it runs on - #1893
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📝 WalkthroughWalkthroughThe L3 hierarchy name changes from ChangesL3 node terminology
Estimated code review effort: 3 (Moderate) | ~20 minutes Merge Risk: 🔵 Low · up to The PR renames the topology-level term from host to node while preserving processor-level host identifiers. A few explanatory references still use host for the topology family, creating limited documentation and maintenance ambiguity without demonstrated runtime impact; the change is mergeable with owner follow-up. Possibly related PRs
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Inline comments:
In `@src/common/hierarchical/types.h`:
- Around line 160-162: Update the comment describing node.post_fence_retirement
to call the measured amount “node-level cost” instead of “host cost,” unless
host is explicitly intended as processor terminology; keep the explanation of
the release_run span unchanged.
Apply the same fix in `@docs/dfx/host-trace.md` around lines 126 - 130: Update
test descriptions referring to the host level word or host family.
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📒 Files selected for processing (14)
conftest.pydocs/dfx/host-trace.mddocs/hierarchical-level-runtime.mdpython/simpler/worker.pypython/simpler/worker_level.pysimpler_setup/scene_test.pysimpler_setup/tools/strace_timing.pysrc/common/hierarchical/types.hsrc/common/log/include/common/host_span_names.htests/ut/cpp/a5/test_host_log_off.cpptests/ut/cpp/hierarchical/test_scheduler.cpptests/ut/py/test_scene_level_selection.pytests/ut/py/test_strace_timing.pytests/ut/py/test_worker/test_host_worker.py
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`host` meant two things at once. It names a **processor** — the CPU that
`HostLogger`, the `host_span` ABI, `host_runtime.so` and `SIMPLER_HOST_STRACE`
all belong to, opposite `device` — and it also named **L3**, a position in the
orchestration tree. Those are different axes, and one word occupied a cell in
each.
The ambiguity had already produced a misread inside the tracer:
host_entries = [entry for entry in entries if not entry[0].is_device]
That `host` is the processor sense, so `host_entries` **includes `chip.run`** —
the same function later returns `"chip child"` for one of those lanes. A reader
who takes the name at face value expects the host *family*.
Which side to rename is not a free choice. The processor sense has 450+
occurrences (`HostLogger` 105, `host_span` 104, `host_log` 103, `host_runtime`
121, `SIMPLER_HOST_STRACE` 26) and `host`/`device` is the CUDA/CANN convention
that every Ascend reader arrives with. The level sense has about 60, behind a
single source of truth. So the level word moves.
L3 is `node`, which is not a new coinage: `python/simpler/global_comm_domain.py`
already calls it that — `node_worker_id`, "one receiving L3 node",
"receiver-node by rank attachment matrix" — and it does so in the communication
code, where `network1`/`network2`/`network3` are the neighbouring coordinates.
The ladder now reads as one system:
core(0) chip(2) node(3) network1(4) network2(5) network3(6)
**Every word is a topology position; none is a processor or a deployment fact.**
That is the same reason L4 is not called `pod`: a node sometimes sits under a
pod and sometimes directly under a supernode, so the level counts hops instead.
L3 running on a host CPU is a deployment fact of exactly that kind — L4 runs
there too, and so does part of the chip runtime, which is why a level word taken
from a deployment location can never be exclusive.
What moved, by the one judgement each occurrence needs — does this `host` name a
level or a processor:
* `WorkerLevel.host` -> `node`, and `SceneTestLevel.HOST` -> `NODE`.
* The parser's copy of the ladder: `_HOST_WORDS` -> `_NODE_WORDS`, the family
`span_family` answers -> `"node"`, `host_span_leaf` -> `node_span_leaf`. The
family still takes its lowest member's name, as before.
* `host_span_names.h`'s pre-bind default word.
* 41 `host.<leaf>` span literals across docs and tests.
Two names that were products of the same ambiguity move with it, because fixing
one sense and leaving these would only half-resolve it:
* `_ROUNDS_TABLE_NAMES` keyed `chip.run` under `"host"` — a level word pointing
at another level's span, 270 lines from the tuple that defines `host` as L3.
The key is `"run"`, which is what the value is. It is an internal dict key;
the printed column header lives in `_ROUNDS_TABLE_COLUMNS` and is untouched,
so `tools/benchmark_rounds.sh` parses exactly what it did before.
* `host_entries`/`host_pids`/`host_threads` -> `non_device_*`, and
`_host_thread_name` -> `_lane_name`, which is what it computes.
What deliberately did not move:
* Every processor-sense identifier, all 450+ of them, including
`to_host_swimlane` (its subject is non-device spans) and the `--trace-out`
lane label `"host"` that sits directly beside `"device (clk=dev)"` — the
single occurrence a mechanical sweep would most likely have broken.
* `docs/hierarchical-level-runtime.md`'s second column. It is the Ascend
architecture documentation's code for each level, not an identifier of ours,
and `HOST` there is correct. L3 is now the row where all three columns
differ — `node` / `HOST` / Node — so the doc states what each column is,
since it never did and L3 is exactly where that mattered.
Two places said `host` where the word was carrying no information at all, so they
lose it rather than pick a side: `RunState::trace_terminal_ns`'s comment measured
"the only host cost outside every other span" and now says the only *work this
process does* there, and the span table's header column was "Host decision point"
inside a section already titled "Host scheduler spans".
Two findings from hw-native-sys#1886's review land here, since that PR merged first and both
are in the code this one renames.
`external_producer` documented "all three segments are required" and checked two
of them, so `ext.pypto.` — a producer with no span of its own — attributed to
`pypto`. It now requires all three to be present *and* non-empty, which also
rejects `ext.pypto..detail`.
`_process_label` was handed only the non-device spans, so a process that emitted
one of our `clk=dev` spans alongside an external host span was labelled as the
producer's. A device span never reaches the visible timeline, but it is still
ours and therefore still evidence about whose process this is; classification now
reads every span the pid emitted. The visible timeline is unchanged.
Verification:
- `pytest tests/ut/py` — 1646 passed, 0 failed; 45 of them in the strace file.
- `ctest -LE requires_hardware` — 101/101. `test_scheduler.cpp` asserting
`node.dispatch` is what proves the C++ side emits it: that name is built from
the bound prefix, so a green run is the end-to-end check for the level word.
- `git grep` for `host_span_leaf`, `_HOST_WORDS`, `WorkerLevel.host` and
`SceneTestLevel.HOST` returns nothing. Every surviving `` `host` `` in prose is
a sentence explaining that it names the processor.
- The ladder-to-parser pin from hw-native-sys#1886 fails if the two lists ever disagree
again, so this rename cannot half-land.
- Both hw-native-sys#1886 findings have a negative control: restoring either the two-segment
check or the non-device-only classification turns exactly its own test red.
- ruff, ruff format clean.
This was referenced Aug 20, 2026
ChaoWao
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that referenced
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Aug 20, 2026
) Reviewing #1875 turned up how a rename can go silently wrong. That PR adds EXPECT_FALSE(captured_host_span("host.dispatch")); on a base that predates #1893, where the word became `node`. Rebasing produces no conflict — the line is new, not edited — so the assertion looks for a name nothing emits, `captured_host_span` answers false, and `EXPECT_FALSE(false)` **passes**. The test that exists to prove a disabled gate emits nothing would then pass whether the gate works or not. Ranked by when you find out, that is the worst of the three outcomes a rename can have: a conflict is immediate, a red test is one CI run, and a vacuously-true assertion is never. What makes it silent is the negated form — the same staleness under `EXPECT_TRUE` merely goes red. Two changes, and the first is not a new guard but the removal of what made the guard necessary. **The names come from the table the emitter uses.** Eight literals in `test_scheduler.cpp` are now `host_span_name(HostSpan::Dispatch)` and friends. These tests assert that a decision point emitted at all; the name is not their subject, so writing it out was a second copy of it. Taking it from the single source means a rename cannot leave them behind — verified by renaming the level word to `network9` and re-running: the suite stays green because the assertions follow. Under the old literals the same rename would have reddened the `EXPECT_TRUE` ones and silently passed an `EXPECT_FALSE` one. **The C++ pre-bind default is pinned to the ladder.** `host_span_names.h`'s `level_word()` defaults to `"node"`, which was a third hand-written copy of the L3 word: `WorkerLevel` is the source of truth, `strace_timing.py`'s `_NODE_WORDS` is pinned to it by its own test, and this one was pinned to nothing. A level renamed in Python would leave C++ emitting the old word for every span before a Worker binds the prefix, with no test noticing. The pin reads that default through the existing binding rather than adding a symbol: `set_level_prefix("")` returns early without binding, while the binding still reports what is in effect. It runs in a child process because the prefix freezes on first bind, so a Worker constructed anywhere in this process would leave the *bound* word behind instead of the default. `test_graph_failure_still_emits_graph_build_span` also spelled out `node.graph_build`; it now builds the expected name from the worker's own `_host_span_prefix`, which is the contract that assertion is about. Verification: - `pytest tests/ut/py` — 1657 passed, 0 failed. - `ctest -LE requires_hardware` — 107/107. - Negative control for the pin: setting the C++ default back to `"host"` fails `test_the_cpp_pre_bind_level_word_is_the_ladder_word_for_l3` and nothing else. - Negative control for the double-write removal: renaming the level word to `network9` keeps `test_scheduler` green, where a literal would have gone red or, worse, vacuously true. Not every literal span name is a double-write, and the distinction is which side of the test it sits on. A literal that **constructs input** — the `SimplerHostSpan` fed to the logger in `test_host_log_off.cpp`, the fake log lines in `test_strace_timing.py` — is right to be written out: the test owns its input, and it is exercising encoding or parsing over an arbitrary name. A literal that **asserts the implementation emitted a particular name** is the second copy, and that is the class both changes above remove. The eight in `test_scheduler.cpp` were the only ones of that kind. What this does not cover, stated because "renames are guarded now" would be too broad a claim: the pin ties the C++ *default* word to the ladder, not every place a name could be spelled out. `git grep -n '"\(node\|network[123]\)\.'` before landing a rename, and judge each hit by the input-versus-assertion test above.
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Summary
hostmeant two things at once:It occupied a cell in each. The ambiguity had already produced a misread inside the tracer:
That
hostis the processor sense, sohost_entriesincludeschip.run— the same function later returns"chip child"for one of those lanes. A reader who takes the name at face value expects the host family.Which side moves is not a free choice
HostLogger105,host_span104,host_log103,host_runtime121,SIMPLER_HOST_STRACE26host/deviceis the CUDA/CANN convention every Ascend reader arrives withSo the level word moves. It is
node, which is not a new coinage —python/simpler/global_comm_domain.pyalready calls L3 that (node_worker_id, "one receiving L3 node", "receiver-node by rank attachment matrix"), and it does so in the communication code, wherenetwork1/2/3are the neighbouring coordinates.Every word is now a topology position; none is a processor or a deployment fact. That is the same reason L4 is not called
pod: a node sometimes sits under a pod and sometimes directly under a supernode, so the level counts hops instead. L3 running on a host CPU is a deployment fact of exactly that kind — L4 runs there too, and so does part of the chip runtime, which is why a level word taken from a deployment location can never be exclusive.What moved
Each occurrence needed one judgement: does this
hostname a level or a processor?WorkerLevel.host→node,SceneTestLevel.HOST→NODE_HOST_WORDS→_NODE_WORDS, the familyspan_familyanswers →"node",host_span_leaf→node_span_leaf(the family still takes its lowest member's name)host_span_names.h's pre-bind default word — the only level-word literal in C++, since the prefix is bound at runtime from Pythonhost.<leaf>span literals across docs and testsTwo names that were products of the same ambiguity move with it, because fixing one sense and leaving these would only half-resolve it:
_ROUNDS_TABLE_NAMESkeyedchip.rununder"host"— a level word pointing at another level's span, 270 lines from the tuple defininghostas L3. The key is"run", which is what the value is. It is an internal dict key; the printed column header lives in_ROUNDS_TABLE_COLUMNSand is untouched, sotools/benchmark_rounds.shparses exactly what it did before.host_entries/host_pids/host_threads→non_device_*,_host_thread_name→_lane_nameWhat deliberately did not move
to_host_swimlane(its subject is non-device spans) and the--trace-outlane label"host"sitting directly beside"device (clk=dev)"— the single occurrence a mechanical sweep would most likely have broken.docs/hierarchical-level-runtime.md's second column. It is the Ascend architecture documentation's code for each level, not an identifier of ours, andHOSTthere is correct. L3 is now the row where all three columns differ —node/HOST/ Node — so the doc states what each column is, which it never did and L3 is exactly where that mattered.Two findings from #1886's review
That PR merged first and both live in the code this one renames:
external_producerdocumented "all three segments are required" and checked two of them, soext.pypto.— a producer with no span of its own — attributed topypto. It now requires all three present and non-empty, which also rejectsext.pypto..detail._process_labelwas handed only the non-device spans, so a process emitting one of ourclk=devspans alongside an external host span was labelled as the producer's. A device span never reaches the visible timeline, but it is still ours and therefore still evidence about whose process this is; classification now reads every span the pid emitted. The visible timeline is unchanged.Testing
pytest tests/ut/py— 1646 passed, 0 failed (45 in the strace file)ctest -LE requires_hardware— 101/101.test_scheduler.cppassertingnode.dispatchis what proves the C++ side emits it: that name is built from the bound prefix, so a green run is the end-to-end check for the level word.span_prefix(3)→node,_set_host_span_level_prefixreturnsnodegit grepforhost_span_leaf,_HOST_WORDS,WorkerLevel.host,SceneTestLevel.HOSTreturns nothing; every surviving`host`in prose is a sentence explaining that it names the processor_emit_host_spanviaHostLogger::log_host_span, external span on the swimlane and absent from the invocation viewsThe ladder-to-parser pin added in #1886 fails if the two lists ever disagree again, so this rename cannot half-land.