Re: Lightweight packet timestamping

Federico Parola <[email protected]> writes:

> On 06/06/20 01:34, David Ahern wrote:
>> On 6/4/20 7:30 AM, Federico Parola wrote:
>>> Hello everybody,
>>> I'm implementing a token bucket algorithm to apply rate limit to traffic and I need the timestamp of packets to update the bucket. To get this information I'm using the bpf_ktime_get_ns() helper but I've discovered it has a non negligible impact on performance. I've seen there is work in progress to make hardware timestamps available to XDP programs, but I don't know if this feature is already available. Is there a faster way to retrieve this information?
>>> Thanks for your attention.
>>>
>> bpf_ktime_get_ns should be fairly light. What kind of performance loss
>> are you seeing with it?
> I've run some tests on a program forwarding packets between two 
> interfaces and applying rate limit: using the bpf_ktime_get_ns() I can 
> process up to 3.84 Mpps, if I replace the helper with a lookup on a map 
> containing the current timestamp updated in user space I go up to 4.48
> Mpps.

Can you share more details on the platform you're running this on? I.e.,
CPU and chipset details, network driver, etc.

-Toke