- gpuBandwidthSocketGroups: a single GPU whose NUMA node fails to resolve
no longer collapses the whole per-socket nvbandwidth split into one
fallback pass — it now folds into the last resolved group instead,
preserving isolation for the sockets that did resolve.
- blackbox discoverMarkedTargets: skip mounting/unmounting devices that
already have a running worker on every 2s discovery tick. This was
observed hammering the same USB target continuously (mount+unmount
every ~2s for the whole session) and contending with the worker's own
sync cycle, plausibly explaining multi-minute sync cycles seen on a
real crash bundle.
- syncFilesystem now calls syscall.Sync() directly instead of spawning
/bin/sync per copied file; blackbox mounts removable targets with
-o sync so writes are durable without relying on the app-level sync as
the primary mechanism.
- New platform.SetSyncBracketHook / satJob.syncBracket: blocks (with a
bounded timeout) on blackbox actually reaching removable media right
before and right after a diagnostic's real load step (nvbandwidth,
memtester, stress-ng, dcgmi diag, nccl, smartctl/nvme self-test...),
instead of only firing a fire-and-forget kick after the job's own log
file is written. A crash mid-load now has durable evidence the load
started, not just whatever streamed to the RAM-backed export dir before
blackbox's next scheduled cycle.
Found investigating a real support bundle where blackbox's last
successful sync (19:55:25) predated both the previous job finishing and
the crashing nvbandwidth job starting (19:56:57) — none of the crash
window ever reached durable media.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
On multi-socket systems, run the NVIDIA bandwidth diagnostic once per
CPU socket before the all-GPU pass, so a crash confined to the all-GPU
run (with clean per-socket passes preceding it) isolates a cross-socket
peer-to-peer fault instead of leaving it conflated with a general
GPU/PCIe issue. Single-socket systems keep the original one-pass shape.
Also expand the support-bundle README with reference notes distilled
from a real analysis pass (BMC clock drift, "0/empty" tool output
meaning absent hardware rather than a fault, timestamp-matching before
assigning causality, and a normal-power-cycle SEL signature), plus a
step-by-step recipe for diagnosing an unexpected reboot/crash during a
specific test.
Mikhail Chusavitin