DF2284: M_DEVBUF before: 211 K
DF2284: queued 400 write-only sg requests, no read() issued
DF2284: M_DEVBUF after writes: 1011 K (delta 800 K; predicted ~26 K)
DF2284: holder pid 879 parks with fd open (external phases: vmstat, then kill -9 879)