timestamp_utc: 2026-06-03T07:43:19Z
purpose: Check whether O_DIRECT open/write fails on /dev/shm for this cluster/kernel.

headnode:
  host: ip-10-0-0-235
  /dev/shm: open_ok, write_ok
  /tmp: open_ok, write_ok

compute_node:
  host: i192bigmem-dy-all-1
  /dev/shm: open_ok, write_ok
  /tmp: open_ok, write_ok

interpretation:
  - On this kernel, a tiny O_DIRECT open/write probe does not fail on /dev/shm.
  - O_DIRECT remains semantically unhelpful for tmpfs because /dev/shm is memory-backed, not a block-device-backed filesystem where bypassing the page cache improves disk I/O.
  - Current BCL Convert commands explicitly use --shared-thread-odirect-output false, so O_DIRECT is not the current observed failure mode.
