diff --git a/sys/conf/NOTES b/sys/conf/NOTES index dfa3d8d8a065..91cf86fa9c40 100644 --- a/sys/conf/NOTES +++ b/sys/conf/NOTES @@ -880,8 +880,8 @@ options ACCEPT_FILTER_HTTP # 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 "options HZ=1000" to achieve a -# smoother scheduling of the traffic. +# DUMMYNET it is advisable to also have at least "options HZ=1000" to achieve +# a smooth scheduling of the traffic. options DUMMYNET # Zero copy sockets support. This enables "zero copy" for sending and @@ -1110,13 +1110,13 @@ options MAC_TEST # CLOCK OPTIONS # The granularity of operation is controlled by the kernel option HZ whose -# default value (100) means a granularity of 10ms (1s/HZ). -# Some subsystems, such as DUMMYNET, might benefit from a smaller -# granularity such as 1ms or less, for a smoother scheduling of packets. -# Consider, however, 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. +# 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. options HZ=100