Ethernet device polling(3)

i386/conf/NOTESより:

#####################################################################
# NETWORKING OPTIONS

#
# DEVICE_POLLING adds support for mixed interrupt-polling handling
# of network device drivers, which has significant benefits in terms
# of robustness to overloads and responsivity, as well as permitting
# accurate scheduling of the CPU time between kernel network processing
# and other activities. The drawback is a moderate (up to 1/HZ seconds)
# potential increase in response times.
# It is strongly recommended to use HZ=1000 or 2000 with DEVICE_POLLING
# to achieve smoother behaviour.
# Additionally, you can enable/disable polling at runtime with help of
# the ifconfig(8) utility, and select the CPU fraction reserved to
# userland with the sysctl variable kern.polling.user_frac
# (default 50, range 0..100).
#
# Not all device drivers support this mode of operation at the time of
# this writing. See polling(4) for more details.

options DEVICE_POLLING

#####################################################################

そうかなとは思ってたけど、やはりHZは1000・2000辺りに設定しないと適切なパフォーマンスは出せないのですね。
CPU fraction reserved to userlandというのはなんだろう。