Static SWAP_PAGEOUT 

static SWAP_PAGEOUT: AtomicBool

Process-global toggle for MADV_PAGEOUT on the lz4 + swap spill path.

When set, ColumnPager::page issues MADV_PAGEOUT over the compressed bytes it keeps resident in CompressedInner::Memory, proactively evicting them at spill time instead of leaving them for lazy kernel reclaim. A single process-global flag (set by apply_tiered_config) mirrors the backend / codec selection: it is a process-wide operational choice, not a per-column one, and every consumer of the shared pager reads the same value. Defaults to off; the eager-reclaim syscall stays gated until proven.