memory-stats reads /proc/self/smaps by default on Linux: every sample formats and parses one
block per mapping while holding the mmap lock. The benches' RssSampler polls it every 2 ms, so
on a profile of bevel_bench --size 4000x3000 the rss-sampler thread was ~22% of all samples
(smaps_account 14.7%, smaps_pte_entry 6.3%), contending with the measured threads.
Enable the crate's always_use_statm feature: one short read of the kernel's RSS counters, the
same number VmRSS reports. The measured code is unchanged; only the harness overhead goes.
xsvm