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vllm-omni/benchmarks/edge_harness/memory_ledger.py
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"""Where the resident memory actually is, by attribution rather than subtraction.
The report's breakdown was arithmetic: weights, imports, and "unexplained
~1.6 GB" left over after subtracting the first two from the total. Three
problems with that. It assigned a bf16 embedding to a checkpoint whose config
says ``quantize_embedding: true``; it left the prefill duplicate out of the
weight line entirely; and a remainder computed from two wrong terms is not a
measurement of anything.
So this counts instead:
* **Unique tensor storages.** Walking ``named_parameters`` double-counts tied
weights -- Spark ties its embedding to its head, and the quantized path ties
five tensors at once -- so storages are keyed by ``data_ptr`` and counted
once, and the tied ones are reported separately rather than silently
dropped.
* **The KV cache**, found by attribute rather than assumed from a formula --
and split into *allocated* and *resident*. A cache that has been allocated
but never written costs address space, not memory, so counting its size as
attributed memory would hide the remainder rather than explain it.
Residency comes from ``mincore(2)``, which reports per-page whether a
mapping is actually in core.
* **Every mapping in /proc/self/smaps**, bucketed into heap, anonymous, file
and the rest. ``smaps_rollup`` cannot do this: it is an aggregate, which is
the whole thing this is trying to break apart.
What it cannot do is attribute native allocations that no longer belong to a
live tensor -- freed allocator arenas, inductor's generated code, transient
buffers the caching allocator is holding. Those land in "unattributed anon",
and the point of the exercise is to see how big that really is once the
attributable part is counted properly.
"""
from __future__ import annotations
import argparse, collections, json, os, sys
sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
from bench_harness import provenance # noqa: E402
def resident_mb(ptr: int, nbytes: int) -> float:
"""How much of a mapping is actually in core, via mincore(2).
Allocated is not resident: an untouched KV cache is address space. Without
this the ledger would "explain" memory the process never used.
"""
import ctypes
if nbytes <= 0:
return 0.0
page = os.sysconf("SC_PAGE_SIZE")
start = ptr - (ptr % page) # mincore needs a page boundary
length = nbytes + (ptr - start)
pages = (length + page - 1) // page
vec = (ctypes.c_ubyte * pages)()
libc = ctypes.CDLL("libc.so.6", use_errno=True)
if libc.mincore(ctypes.c_void_p(start), ctypes.c_size_t(length), vec) != 0:
return -1.0 # unknown, rather than a guess
return round(sum(v & 1 for v in vec) * page / 2**20, 1)
def _rss(field: str) -> float:
with open("/proc/self/status") as f:
for line in f:
if line.startswith(field):
return round(int(line.split()[1]) / 1024, 1)
return 0.0
def smaps_breakdown() -> dict[str, float]:
"""Anonymous resident bytes per mapping kind. Needs smaps, not rollup."""
buckets: collections.Counter = collections.Counter()
name = "[anon]"
try:
with open("/proc/self/smaps") as f:
for line in f:
if not line[:1].isspace() and "-" in line.split()[0]:
parts = line.split()
path = parts[5] if len(parts) > 5 else "[anon]"
if path.startswith("["):
name = path
elif path.endswith(".so") or ".so." in path:
name = "shared libs"
elif path:
name = "file-backed"
else:
name = "[anon]"
elif line.startswith("Anonymous:"):
buckets[name] += int(line.split()[1])
except OSError:
return {}
return {k: round(v / 1024, 1) for k, v in buckets.most_common()}
def storage_ledger(model) -> dict:
"""Unique tensor storages, by role, counting each byte once."""
import torch
seen: dict[int, int] = {}
biggest: list = []
by_role: collections.Counter = collections.Counter()
counts: collections.Counter = collections.Counter()
tied_bytes = 0
def role_of(name: str) -> str:
low = name.lower()
if "embed" in low or "lm_head" in low:
return "embedding / head"
for key in ("int4pack", "halves", "scales_and_zeros", "group_scale",
"group_zero", "weight_scale", "weight_zero", "weight_packed"):
if key in low:
return f"quant:{key}"
if "weight" in low:
return "other weights"
return "other"
for name, tensor in list(model.named_parameters()) + list(model.named_buffers()):
if not isinstance(tensor, torch.Tensor) or tensor.device.type != "cpu":
continue
try:
ptr = tensor.untyped_storage().data_ptr()
nbytes = tensor.untyped_storage().nbytes()
except Exception:
ptr, nbytes = tensor.data_ptr(), tensor.numel() * tensor.element_size()
if ptr in seen:
tied_bytes += nbytes # tied / shared: counted once already
continue
seen[ptr] = nbytes
by_role[role_of(name)] += nbytes
counts[role_of(name)] += 1
if nbytes >= 16 * 2**20:
biggest.append((name, nbytes, resident_mb(ptr, nbytes),
tuple(tensor.shape), tensor.dtype))
biggest.sort(key=lambda t: -t[1])
return {
"unique_storage_mb": round(sum(seen.values()) / 2**20, 1),
"tied_duplicate_mb": round(tied_bytes / 2**20, 1),
"by_role_mb": {k: round(v / 2**20, 1) for k, v in by_role.most_common()},
"tensors_by_role": dict(counts),
# "other" is where an unclassified tensor hides, so name the largest
"largest_tensors": [
{"name": n, "mb": round(b / 2**20, 1), "resident_mb": r,
"shape": list(sh), "dtype": str(dt)}
for n, b, r, sh, dt in biggest[:15]
],
}
def main() -> None:
ap = argparse.ArgumentParser()
ap.add_argument("--model", required=True)
ap.add_argument("--quantization", default=None)
ap.add_argument("--max-model-len", type=int, default=2048)
ap.add_argument("--tag", default="ledger")
ap.add_argument("--out", required=True)
a = ap.parse_args()
anon_before = _rss("RssAnon:")
import vllm_omni # noqa: F401
import torch
from vllm import LLM
anon_after_import = _rss("RssAnon:")
llm = LLM(model=a.model, dtype="bfloat16", max_model_len=a.max_model_len,
max_num_seqs=1, quantization=a.quantization,
enable_prefix_caching=False, trust_remote_code=False,
disable_log_stats=True)
# The model only exists in this process when the executor stayed uniproc;
# say so rather than reporting a ledger of nothing.
try:
engine = llm.llm_engine
runner = engine.engine_core.engine_core.model_executor.driver_worker.model_runner
model = runner.model
except AttributeError as exc:
raise SystemExit(
f"cannot reach the model in this process ({exc}). Set "
f"VLLM_ENABLE_V1_MULTIPROCESSING=0 so the executor stays uniproc; "
f"otherwise the weights are in a worker and there is nothing here "
f"to attribute."
)
ledger = storage_ledger(model)
kv_mb = kv_resident = 0.0
try:
caches = runner.kv_caches
seen = set()
for c in caches:
if isinstance(c, torch.Tensor) and c.data_ptr() not in seen:
seen.add(c.data_ptr())
nbytes = c.numel() * c.element_size()
kv_mb += nbytes / 2**20
r = resident_mb(c.data_ptr(), nbytes)
kv_resident += max(r, 0.0)
except Exception:
kv_mb = kv_resident = -1.0
anon_total = _rss("RssAnon:")
# Only resident KV counts: allocated-but-untouched cache is address space.
attributed = (ledger["unique_storage_mb"] + max(kv_resident, 0.0)
+ anon_after_import)
rec = {
"tag": a.tag, "model": a.model, "quantization": a.quantization,
"anon_before_import_mb": anon_before,
"anon_after_import_mb": anon_after_import,
"anon_total_mb": anon_total,
"kv_cache_allocated_mb": round(kv_mb, 1),
"kv_cache_resident_mb": round(kv_resident, 1),
**ledger,
"attributed_mb": round(attributed, 1),
"unattributed_anon_mb": round(anon_total - attributed, 1),
"smaps_anon_mb": smaps_breakdown(),
"provenance": provenance({"scope": "in-process ledger"}),
}
print(json.dumps({k: v for k, v in rec.items() if k != "provenance"}, indent=2))
with open(a.out, "w") as f:
json.dump(rec, f, indent=2)
if __name__ == "__main__":
main()