Re: [Linuxptp-users] Expected throughput of the ptp4l

[Richard C. <ric...@gm...>]

On Wed, Mar 18, 2015 at 02:58:46AM +0000, Chandra Mallela wrote:
> From my interactions with the customer as an architect, I could see the need for 512 syncs per second, due to high-end frequency correction (think of a 1588 application to replace/compete with SyncE applicationIn a pure telecom application, high frequency Sync packets might encroach into datatraffic. However, in back-hauling (be it telecom or networking), where high-throughput is already a given parameter, high frequency Sync packets are desirable for frequency corrections. ). On offset correction, I can take liberties on DelayReq sets.

If you have SyncE in place already, then you don't need the 512 rate.
In fact, all you need is *one* offset measurement in order to correct
the offset, once the clocks are locked.

If you are trying to replace a SyncE system with a non-SyncE PTP
system, then you can forget trying to match the SyncE synchronization
performance.  It just is not feasible, to my knowledge.
 
> Do we have the performance metrics of the ptp4l in a standard Linux OS? At what rates of the packets, does the stack break down? If we have any data, it will be good for us to know. If you have any ideas as to how to arrive at the numbers, please let me know - I can try it out with the system at my hand.

The answer is, "it depends."

I have seen good results with 1, 2, 4, and 8, packets per second on a
low end embedded system.  With 128, some time stamps are dropped due
to hardware/driver constraints.

Any performance metric is tied to the particular hardware used, and so
even if I had such metrics, they would not help you too much.

I already told you this more than once: If you really want to run 512
packets per second, then you are going to have to do some careful
hardware selection and some serious system tuning.

It won't be easy.

Good luck,
Richard