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authorLuigi Rizzo <luigi@FreeBSD.org>2001-12-14 23:25:58 +0000
committerLuigi Rizzo <luigi@FreeBSD.org>2001-12-14 23:25:58 +0000
commitc578eeb389b235ed2c339eab75e5a3d9fb00b612 (patch)
treea3a033fbe4ced0f9c9a680608a8fc39e89099c9c /sys/conf/NOTES
parent9ea42c8e3498c9b10898820d5dc61887c22e67ac (diff)
downloadsrc-c578eeb389b235ed2c339eab75e5a3d9fb00b612.tar.gz
src-c578eeb389b235ed2c339eab75e5a3d9fb00b612.zip
Clarify the comments related to DUMMYNET and HZ
MFC after: 3 days
Notes
Notes: svn path=/head/; revision=87962
Diffstat (limited to 'sys/conf/NOTES')
-rw-r--r--sys/conf/NOTES19
1 files changed, 12 insertions, 7 deletions
diff --git a/sys/conf/NOTES b/sys/conf/NOTES
index cbf8f9a0a2b5..3fd76efe7487 100644
--- a/sys/conf/NOTES
+++ b/sys/conf/NOTES
@@ -638,9 +638,13 @@ options ACCEPT_FILTER_HTTP
options TCP_DROP_SYNFIN #drop TCP packets with SYN+FIN
# DUMMYNET enables the "dummynet" bandwidth limiter. You need
-# IPFIREWALL as well. See the dummynet(4) manpage for more info.
+# IPFIREWALL as well. See the dummynet(4) and ipfw(8) manpages for more info.
+# When you run DUMMYNET it is advisable to also have "options HZ=1000"
+# to achieve a smoother scheduling of the traffic.
+#
# BRIDGE enables bridging between ethernet cards -- see bridge(4).
-# You can use IPFIREWALL and dummynet together with bridging.
+# You can use IPFIREWALL and DUMMYNET together with bridging.
+#
options DUMMYNET
options BRIDGE
@@ -832,11 +836,12 @@ options _KPOSIX_VERSION=199309L
# CLOCK OPTIONS
# The granularity of operation is controlled by the kernel option HZ whose
-# default value (100) means a granularity of 10ms. For an accurate simulation
-# of high data rates it might be necessary to reduce the timer granularity to
-# 1ms or less. Consider, however, that some interfaces using programmed I/O
-# may require a considerable time to output packets. So, reducing the
-# granularity too much might actually cause ticks to be missed thus reducing
+# 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.
options HZ=100