> From: Stephen Hemminger [mailto:[email protected]]
> Sent: Thursday, 18 June 2026 17.23
>
> On Thu, 18 Jun 2026 10:38:15 -0400
> Dawid Wesierski <[email protected]> wrote:
>
> > + * @param ts
> > + * Packet timestamp in nanoseconds since the Unix epoch. If zero,
> the
> > + * current TSC is captured and converted to epoch ns by
> > + * rte_pcapng_write_packets() when the packet is written.
> > *
>
> It might help users if a helper rte_tsc_to_epoch() was exposed.
+1
Please note that such a helper would need to compensate for rte_rdtsc() drift.
Simplified:
int64_t rte_tsc_to_ns(tsc)
{
struct timespec ts = clock_gettime(CLOCK_REALTIME);
int64_t now_ns = ts.tv_sec * NS_PER_S + ts.tv_nsec;
int64_t now_tsc = rte_rdtsc();
int64_t diff_tsc = tsc - tsc_now;
return now_ns + diff_tsc * NS_PER_S / rte_get_tsc_hz();
}
A performance optimized version would take "now_ns" and "now_tsc" as parameters.
And with "now_ns" passed as a parameter, the function also works with other
clocks, such as CLOCK_MONOTONIC.
Also see this discussion on the Grout mailing list:
https://inbox.dpdk.org/grout/[email protected]/T/#m465a04ca2e8219612dd9c3efb4198d23d5813422
