PR_FASTHZ
callout_schedule(&pffasttimo_ch, hz / PR_FASTHZ);
IGMP_MAX_HOST_REPORT_DELAY * PR_FASTHZ);
timer = igmp->igmp_code * PR_FASTHZ / IGMP_TIMER_SCALE;
IGMP_MAX_HOST_REPORT_DELAY * PR_FASTHZ);
#define TCP_DELACK_TICKS (hz / PR_FASTHZ) /* time to delay ACK */