pub const WPROF_MIN_MEMORY_MIB: u32 = 2048;Expand description
Minimum guest memory (MiB) for test entries that enable wprof.
Derivation: WprofConfig::default_args requests
--ringbuf-size=256000 --ringbuf-cnt=8. wprof rounds the
256000 KB request up to the next power of two (262144 KB =
256 MiB) per ringbuf, times 8 ringbufs = 2048 MiB BPF arena.
On guests below this, wprof OOM-kills mid-run before it can
emit the Perfetto .pb trace, producing a truncated artifact
and a confused test author.
Applied as a floor by
crate::test_support::runtime::derive_test_memory_mib —
the single derivation site shared by the entry-derived
topology path AND every dispatch site that constructs a
crate::test_support::topo::TopoOverride from CLI / preset
topology (so e.g. cargo ktstr test --ktstr-topo NnNlNcNt and
gauntlet preset runs honor the floor identically). Both
primary and auto-repro VMs route through the same derivation
so the floor propagates to both; identical topology between
the two VMs is also required for stall reproducibility.
The floor applies when the derived memory
max(cpus*64, 256, entry.memory_mib) falls below 2048 MiB
AND entry.wprof is true. An operator-supplied
crate::test_support::topo::TopoOverride with explicit
memory_mib is honored verbatim per the override-is-verbatim
contract — a warn-level log fires when the override conflicts
with the floor, but the operator’s choice wins. Shell-mode VMs
(cargo ktstr shell --kernel ...) bypass this floor entirely;
the operator sets memory size via shell-mode CLI args.
Tracks WprofConfig::default_args: a future change to
--ringbuf-size or --ringbuf-cnt invalidates the 2048
derivation and this const should move with the args.