On Wed, Apr 11, 2012 at 12:52:57AM +0200, Luigi Rizzo wrote: > I noticed this first on a 10G interface, but now there seems > to be a similar issue on the loopback. > > Apparently a ping -f has a much lower RTT than one with non-zero > delay between transmissions. Part of the story could be that > the flood version invokes a non-blocking select. > On the other hand, pinging on the loopback should make > the response available right away, so what could be the reason > for the additional 3..10us in the ping response time ? > > The following are numbers on an i7-2600k at 3400 MHz + turboboost, > running stable/9 amd64. Note how the min ping time significantly > increases moving from flood to 10ms to 1s. > On an Intel 10G interface i am seeing a min of 14-16us with Sorry but I am having trouble wrapping my head around this as the results below are only for the loopback address 127.0.0.1 that does not travel on the wire at all ? Did you assign this to the 10ge interface ? if so which result is which. ? In order to get any good results on my machine I had to tune the following. net.inet.icmp.reply_from_interface=1 net.inet.icmp.icmplim_output=0 net.inet.icmp.icmplim=0 net.inet.icmp.log_redirect=1 You may have other options if this is greater than stable/8 _at_ 234095 But yes the results seem skewed to some extent and being loopback I would think there should be a very near zero rx/tx time. > a ping flood, and up to 33-35us with the standard 1s interval > (using -q probably trims another 2..5us) > > > sudo ping -c 1000 -q -f 127.0.0.1 > round-trip min/avg/max/stddev = 0.002/0.003/0.012/0.001 ms > > sudo ping -c 1000 -q -f 127.0.0.1 > round-trip min/avg/max/stddev = 0.002/0.002/0.013/0.001 ms > > sudo ping -c 1000 -q -f 127.0.0.1 > round-trip min/avg/max/stddev = 0.002/0.002/0.013/0.001 ms > > sudo ping -c 10000 -q -f 127.0.0.1 > round-trip min/avg/max/stddev = 0.002/0.002/0.011/0.001 ms > > > sudo ping -c 1000 -q -i 0.01 127.0.0.1 > round-trip min/avg/max/stddev = 0.005/0.012/0.017/0.001 ms > > sudo ping -c 1000 -q -i 0.01 127.0.0.1 > round-trip min/avg/max/stddev = 0.004/0.012/0.016/0.001 ms > > sudo ping -c 200 -q -i 0.01 127.0.0.1 > round-trip min/avg/max/stddev = 0.007/0.012/0.017/0.002 ms > > sudo ping -c 200 -q -i 0.01 127.0.0.1 > round-trip min/avg/max/stddev = 0.005/0.012/0.018/0.002 ms > > sudo ping -c 200 -q -i 0.01 127.0.0.1 > round-trip min/avg/max/stddev = 0.009/0.012/0.020/0.002 ms > > sudo ping -c 200 -q -i 0.01 127.0.0.1 > round-trip min/avg/max/stddev = 0.006/0.012/0.016/0.001 ms > > > sudo ping -c 200 -q -i 0.1 127.0.0.1 > round-trip min/avg/max/stddev = 0.007/0.014/0.020/0.001 ms > > sudo ping -c 200 -q -i 0.1 127.0.0.1 > round-trip min/avg/max/stddev = 0.006/0.014/0.019/0.002 ms > > sudo ping -c 200 -q -i 0.1 127.0.0.1 > round-trip min/avg/max/stddev = 0.007/0.014/0.021/0.001 ms > > sudo ping -c 200 -q -i 0.1 127.0.0.1 > round-trip min/avg/max/stddev = 0.007/0.014/0.020/0.001 ms > > sudo ping -c 200 -q -i 0.1 127.0.0.1 > round-trip min/avg/max/stddev = 0.006/0.014/0.021/0.002 ms > > sudo ping -c 200 -q -i 0.1 127.0.0.1 > round-trip min/avg/max/stddev = 0.010/0.014/0.022/0.001 ms > > > sudo ping -c 20 -q -i 1 127.0.0.1 > round-trip min/avg/max/stddev = 0.013/0.018/0.022/0.002 ms > > sudo ping -c 20 -q -i 1 127.0.0.1 > round-trip min/avg/max/stddev = 0.012/0.018/0.021/0.002 ms > > sudo ping -c 20 -q -i 1 127.0.0.1 > round-trip min/avg/max/stddev = 0.009/0.017/0.018/0.002 ms > > sudo ping -c 20 -q -i 1 127.0.0.1 > round-trip min/avg/max/stddev = 0.011/0.017/0.021/0.002 ms > > sudo ping -c 20 -q -i 1 127.0.0.1 > round-trip min/avg/max/stddev = 0.010/0.017/0.020/0.002 ms > > sudo ping -c 20 -q -i 1 127.0.0.1 > round-trip min/avg/max/stddev = 0.009/0.017/0.028/0.004 ms > > cheers > luigi > _______________________________________________ > freebsd-net_at_freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe_at_freebsd.org" -- ;s =;Received on Wed Apr 11 2012 - 02:09:53 UTC
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