Claudio Jeker <cje...@diehard.n-r-g.com> writes:
> Don't forget to increase the UDP recvbuffer space. The default is somewhat
> small and will result in drops. At least you should invest some time to
> play with that value and see if it helps.
I played with the net.inet.udp.recvspace sysctl option today. The
maximum allowed value for it is 262144. After that things break (as in
no daemons start, network is disabled and during boot I get the message
ifconfig: socket: No buffer space available). I guess I am reaching some
sort of kernel limit, without producing kernel panic.
With the maximum value I do see udp packet drops in my tests (that
increase as the test provides larger query rates)
root@dmeg-dns1 ~ # netstat -s -p udp
udp:
268217 datagrams received
0 with incomplete header
0 with bad data length field
0 with bad checksum
194 with no checksum
267842 input packets hardware-checksummed
0 output packets hardware-checksummed
130 dropped due to no socket
0 broadcast/multicast datagrams dropped due to no socket
0 dropped due to missing IPsec protection
64705 dropped due to full socket buffers
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
203382 delivered
212059 datagrams output
187019 missed PCB cache
Unfortunately I see no real difference in BIND's performance with the
values I tested (262144, 131072).
--
Kostas Zorbadelos
twitter:@kzorbadelos http://gr.linkedin.com/in/kzorba
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