Accuracy of rte_get_tsc_hz() compared to linux

[Stephen Hemminger]

On Thu, 19 Sep 2024 01:04:40 +0300
Isaac Boukris <iboukris at gmail.com> wrote:

> Hi,
> 
> On Intel(R) Xeon(R) Gold 6130 CPU @ 2.10GHz (see lscpu output at the end).
> 
> The rte_get_tsc_hz() returns 2100000 KHz but using it causes our
> timestamps to lag behind real time (roughly a sec per 10 min). I
> noticed the kernel uses 2095082 KHz and in fact it gives much better
> results.
> 
> dmesg:
> tsc: Detected 2095.082 MHz processor
> 
> tsc_freq_khz (custom kmod to exposes kernel's tsc_khz):
> cat /sys/devices/system/cpu/cpu0/tsc_freq_khz
> 2095082


Sigh. exposing tsc frequency through sysfs is a Redhat extension
that never got merged upstream.