Default udp workers to 1, as it is the most sane choice everywhere, also reflect the new udp parallelism in the man pages

1 files changed, 13 insertions, 1 deletions

diff --git a/opentracker.conf.sample b/opentracker.conf.sample
index 4adb736..1d535e8 100644
--- a/opentracker.conf.sample
+++ b/opentracker.conf.sample
@@ -23,7 +23,7 @@
 #
 #        workers=<count>  handle this udp socket in blocking reads in that
 #                         many dedicated worker threads instead of in the
-#                         event loop. Ignored for tcp.
+#                         event loop. Defaults to 1. Ignored for tcp.
 #        shared           allow another process to bind the same address and
 #                         let the kernel share the traffic. Only useful if you
 #                         deliberately run a second tracker there.
@@ -37,6 +37,18 @@
 # listen.udp.workers 4
 # listen.shared 1
 #
+#      Raising the worker count pays off where the kernel spreads arriving
+#      datagrams over a group of sockets bound to one address. Linux does so
+#      and FreeBSD has since 12.0, Darwin does not. opentracker asks at start
+#      up and binds one socket per worker only where the answer is yes. Where
+#      it is no, all workers read the one socket and contend for its receive
+#      queue, which costs more than it returns. See the TUNING section of
+#      opentracker.conf(5); tests/udp_scaling.py sweeps the setting on the
+#      machine that will carry the traffic.
+#
+#      A count of 0 answers udp from the event loop, in the thread that also
+#      serves tcp, which is what opentracker did before.
+#
 #      Note, that using 0.0.0.0 for udp sockets may yield surprising results.
 #      An answer packet sent on that socket will not necessarily have the
 #      source address that the requesting client may expect, but any address