Hrm, my tests, where I use mili-second timers in data sent
from userspace shows that I can run 100Mbps of TCP, UDP,
and custom Ethernet traffic with less than 1 milisecond of
latency. And that is end-to-end (user-space to user-space).
This is 100Mbps tx and 100Mbps rx at the same time, too...
Maybe you don't mean miliseconds??
ping also shows about .3ms for round-trip on normal fast-ethernet
and modern computers....
Ben
Guilhem Tardy wrote:
>
> Hi all,
>
> I am done with those measurements, and the results are (average of 50 UDP
> packets of 500 bytes, in bunch of 3 every 50 ms, the PC running X but no other
> particularly demanding application):
> from stage 0 to 1: 5.97 msec [eth driver to IP_input]
> from stage 1 to 2: 1.26 msec [IP_input]
> from stage 2 to 3: 1.75 msec [IP_input to UDP]
> from stage 3 to 4: 12.83 msec [UDP to application]
> ---
> Total: 21.75 ms
>
> I have seen variations in those numbers, for example stage 3 to 4 taking over
> 50 ms in another instance of the test. I may rerun another quick test for
> capturing maximum values (and variance?) at a later stage when I compare it to
> a real-time patched kernel, probably for next week.
>
> Technical detail of my implementation are:
> * storing the 32 lower bits of the CPU clock register found in timex.h (this
> is x586 specific and provides less than a usec precision without any
> particular
> performance hit) in each UDP packets received on a particular port (hard coded
> in the 3c59x.c, ip_input.c and udp.c)
> * 'sleep(1)' and a custom rtc interrupt handler (from Rene) used by the
> application to calibrate the number of CPU clock register ticks per second
>
> I will package and release the whole code to anyone interested. Thanks to all
> for your help and suggestions. I learnt quite a lot in doing that.
>
> Guilhem.
>
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--
Ben Greear <greearb@xxxxxxxxxxxxxxx> <Ben_Greear@xxxxxxxxxx>
President of Candela Technologies Inc http://www.candelatech.com
ScryMUD: http://scry.wanfear.com http://scry.wanfear.com/~greear
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