diff --git a/sys/conf/NOTES b/sys/conf/NOTES --- a/sys/conf/NOTES +++ b/sys/conf/NOTES @@ -1047,8 +1047,7 @@ # DUMMYNET enables the "dummynet" bandwidth limiter. You need IPFIREWALL # as well. See dummynet(4) and ipfw(8) for more info. When you run -# DUMMYNET it is advisable to also have at least "options HZ=1000" to achieve -# a smooth scheduling of the traffic. +# DUMMYNET, HZ/kern.hz should be at least 1000 for adequate response. options DUMMYNET # The DEBUGNET option enables a basic debug/panic-time networking API. It @@ -1237,14 +1236,11 @@ ##################################################################### # CLOCK OPTIONS -# The granularity of operation is controlled by the kernel option HZ whose -# default value (1000 on most architectures) means a granularity of 1ms -# (1s/HZ). Historically, the default was 100, but finer granularity is -# required for DUMMYNET and other systems on modern hardware. There are -# reasonable arguments that HZ should, in fact, be 100 still; consider, -# that reducing the granularity too much might cause excessive overhead in -# clock interrupt processing, potentially causing ticks to be missed and thus -# actually reducing the accuracy of operation. +# The granularity of operation is controlled by the kernel option HZ (default +# 1000 or 1ms). Virtual machines guests default to an HZ value of 100. Lower +# values produce less overhead at the expense of reduce accuracy in delivery of +# kernel timeouts. With the adaptive tick code, lower values produce less +# benefit than in the past. options HZ=100