ACT_DECLINE
if (bp->b_act_count < ACT_DECLINE)
bp->b_act_count -= ACT_DECLINE;
__read_mostly static u_int vm_anonmem_decline = ACT_DECLINE;
__read_mostly static u_int vm_filemem_decline = ACT_DECLINE * 2;
m->act_count -= min(m->act_count, ACT_DECLINE);