I tried to measure transmit latency myself. I put some code in
ixgbe_clean_tx_irq and ixgbe_tx_map just before writel(i, tx_ring->tail); and
then I loaded the ixgbe module with InterruptThrottleRate=0 and I'm seeing
times of 7 microseconds to 34 microseconds when the only traffic going
through a very quiet system is one ping command. Does that seem right? It
seems really slow to me, even 7 microseconds seems slow ( a 64 byte udp
send only takes 1.5-2 microseconds ). Any ideas on how to measure this
accurately? Or does Intel publish numbers anywhere. I know the numbers
will vary based on offload, etc but some general range would be a great
place to start.
Thanks,
Doug
On Sat, Sep 27, 2014 at 10:17 PM, Doug Anderson <dfaussie...@gmail.com>
wrote:
> What is, or even better, how do I measure transmit latency. As defined in
> Intel docs transmit latency is measured from tail update until packet is
> transmitted on the wire. The docs give a chart which seems to say 1-2 usec
> for a 64 byte packet ( I'm visually extrapolating figure 7-31 in the Intel
> 82599 data sheet page 398 ).
>
> Thanks,
> Doug
>
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