Date: Tue, 10 Apr 2012 15:40:27 -0700 From: Julian Elischer <julian@freebsd.org> To: Luigi Rizzo <rizzo@iet.unipi.it> Cc: current@freebsd.org, net@freebsd.org Subject: Re: strange ping response times... Message-ID: <4F84B6DB.5040904@freebsd.org> In-Reply-To: <20120410225257.GB53350@onelab2.iet.unipi.it> References: <20120410225257.GB53350@onelab2.iet.unipi.it>
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On 4/10/12 3:52 PM, 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 > a ping flood, and up to 33-35us with the standard 1s interval > (using -q probably trims another 2..5us) I'd suggest some ktr points around the loopback path.. > > 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-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" >
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