Resource information for candidate hosts is injected into the
scheduler once per session (worker push, cached in w->resvals/
w->resInUse); a single session then evaluates many jobs against many
candidate hosts off that one cached snapshot without re-querying
between decisions. Made the reason explicit: a live query per
candidate-host check, at the volume a session performs, would be far
too costly. This is a documentation clarification only -- no
behavior change.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019QxaSzHRB7pmYFp4cVnwkA
A job with no rusage[mem=...] request (reserved=0) was being SKIPPED
entirely during reservation-vs-usage reconciliation, on the mistaken
assumption that "no reservation" meant "nothing needs charging". It
doesn't: this codebase's admission check has no live OS read at
decision time (sched_check_host_satisfy_(), resource.c) -- it compares
the worker's last-reported "mem" value against this scheduler's OWN
tracked resInUse tally, built entirely from summed xce_res_account_t
entries. Skipping an unreserved job left its real, live memory
consumption permanently invisible to that tally -- an actual
over-subscription risk (the scheduler could admit more onto a host
than it can support, believing memory was free that a live process was
genuinely using), not merely a display gap.
Fix: charged = max(reserved, actual) applies to EVERY job, reserved or
not. ensure_host_account_by_resname() (resource.c) now creates a fresh
reserved=0 account entry (resolving residx via key_find() against
core->resmgr, same pattern sched_update_res_accounts() already uses
for a fresh account) instead of skipping when a job has no existing
entry for a resource. Returns NULL (a genuine no-op) only when the
resource isn't registered in the cluster's config at all.
Rewrote resource-accounting.md to correct the mechanism it documented:
"available" is NOT a live OS read (mem vs the similarly-named but
static maxmem was worth naming explicitly too) -- it's worker's
last-reported mem minus this scheduler's own resInUse tally, and that
tally must include every job's real usage regardless of reservation.
Also documented a known, pre-existing property surfaced while
correcting this: since mem's own worker report already reflects real
consumption and the scheduler's charge is a separate layer that
doesn't get cleared on a fresh report, tracking can become
conservative over time (under-utilization risk, never over-
subscription) -- the same direction slots already accepts, and a
separate, larger question than this fix's scope.
Replaced test_reconcile_job_resource_usage_skips_when_no_mem_request
(asserted the now-wrong skip behavior) with two tests: one proving an
unreserved job's real usage is created and charged, one proving a
genuine no-op when "mem" isn't a registered resource at all. Full
scheduler suite: 55/55 passing, zero regressions.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019QxaSzHRB7pmYFp4cVnwkA
Adds reservation-vs-actual-usage reconciliation for real (gauge-style)
resources, using mem as the concrete case -- documented in the new
resource-accounting.md steering doc.
Policy: charged = max(reserved, actual). A job's rusage[mem=...]
request is an estimate made before it has run, and the real usage the
worker later reports may land above or below it; charging a flat
reservation for the job's whole life either starves other jobs of
memory it never uses (when actual stays below the estimate) or lets
the host be driven into genuine oversubscription (when actual exceeds
it). Available memory for scheduling is then the host's OS-reported
available figure minus, per job, only the UNUSED SLACK of the
reservation (max(0, reserved - used)) -- never the job's actual usage
on top of that, since the OS's own figure already reflects it.
The existing xce_res_account_t{used, reserved, allocated} fields and
sched_update_res_accounts()'s used+reserved charge formula already
implement this exactly, once `used` is set to the OVERAGE beyond the
reservation (max(0, actual - reserved)) rather than left at its
permanent 0.0 default -- nothing previously computed it.
New (resource.c): sched_reconcile_host_resource_usage() sets that
overage on one xce_res_account_t and applies just the DELTA to the
affected worker's resInUse (not a full uncharge/recharge of the whole
job_account, which would needlessly re-touch sibling resources like
"slots" charged in the same account). sched_reconcile_job_resource_usage()
is the wrapper driven from a raw rusage report: maps the worker's real
wire resname ("memory_rss", same worker-resname-vs-scheduler-resource-
name split bug-1735 already established for the controller side) to
the scheduler's "mem" resource, and is a no-op when the job spans more
than one host (the wire report carries no per-host attribution today --
a separate, undocumented-until-now gap, out of this fix's scope) or
never requested rusage[mem=...] in the first place (reserved=0, nothing
to reconcile).
Wired into sched_apply_job_rusage() (schedobj.c), which already
receives every job rusage tick but previously only stored it for
display/plugin hooks with no resource-accounting effect at all.
Compatible with sched_account_jobs()'s existing per-round resInUse
reset+re-derive cycle (bug-1624): the reconciled `used` value is
persisted on the job's own account record, which that re-derivation
already reads from, not just a transient pool-level delta that a
round boundary would wipe.
Added link-satisfying stubs to the three white-box test files that
#include schedobj.c directly (test_job_update.c,
test_picker_config_fields.c, test_picker_wiring.c) -- none of them
exercise real job->accounts, so the new call is unreachable there, but
still needs to link. 10 new regression tests in
test_resource_accounting.c cover the core formula (below/at/above the
reservation, delta-only pool updates, sibling-resource isolation) and
the wrapper's scoping rules (resname mapping, multi-host skip,
no-request no-op).
Full scheduler suite: 55/55 passing, zero regressions.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019QxaSzHRB7pmYFp4cVnwkA
