=== step 0: environment ===
DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #1: Tue Oct 13 02:09:45 UTC 2026     root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC  x86_64
hw.physmem: 4257742848
vm.swap_size: 1048512
=== step 1: create 200-page (819200 byte) swap backing file ===
swapfile size before: 819200
=== step 2: attach vn0 and swapon ===
swapon: adding /dev/vn0 as swap device
vm.swap_size delta after swapon: 128 pages (expect +192 = 768KB published; only 136 pages/544KB truly exist in the allocatable stripes)
--- swapinfo: vn0 claims 2048 512-blocks (1MB) on an 800KB file ---
Device          512-blocks     Used    Avail Capacity  Type
/dev/vbd0s1b       8388608        0  8388608     0%    Interleaved
/dev/vn0              1536        0     1536     0%    Interleaved
Total              8390144        0  8390144     0%
=== step 3: churn anonymous memory to drive pageout into the phantom tail ===
churn: touched 4600 MB (1177600 pages), holding 5s
churn: done
=== step 4: evidence ===
swapfile size before churn: 819200
swapfile size after churn : 819200
NOT-REPRODUCED: file unchanged
--- final swapinfo ---
Device          512-blocks     Used    Avail Capacity  Type
/dev/vbd0s1b       8388608    38224  8350384     0%    Interleaved
/dev/vn0              1536     1024      512    67%    Interleaved
Total              8390144    39248  8350896     0%
--- final vm.swap_size ---
vm.swap_size: 1048640
=== step 5: teardown ===
swapoff: removing /dev/vn0 as swap device
done