Which version of vpp are you running? Which Linux kernel is involved? What
kind of hardware? Lastly, did you just start running NTP on the system?
Yes, of course it means something: every N seconds, vpp calculates its idea
of the current clock frequency by asking the kernel [via the clock_gettime (
CLOCK_REALTIME) syscall] what time it is. It asks the CPU for the current
clock tick [on x86_64, via "RDTSC"]. Some arithmetic later, we have a new
clock rate for the processor.
We can't simply believe the new clock rate, because e.g. NTP synchronization
can change the kernel reference clock by minutes or hours. Every timer in
the system breaks catastrophically if vpp's idea of the CPU clock rate is
seriously wrong. After a suitable number of experiments, we decided to
reject frequency changes of more than one percent.
Vpp has to continuously adjust its idea of the current clock rate, otherwise
long-running timers won't be accurate enough.
See .../src/vppinfra/time.c:clib_time_verify_frequency() and
.../src/vppinfra/time.h:clib_time_now_internal() for details.
From: vpp-dev@lists.fd.io <vpp-dev@lists.fd.io> On Behalf Of Gudimetla,
Leela Sankar via lists.fd.io
Sent: Thursday, August 5, 2021 11:31 PM
To: vpp-dev@lists.fd.io
Subject: [vpp-dev] Rejecting large frequency change
Hello,
We have started seeing the below warning message coming continuously.
Traffic is running on several vhost-ports and physical ports. These messages
are coming even after a restart with a slow rate.
VPP clib_warning: clib_time_verify_frequency:248: Rejecting large frequency
change of 1.01%
Does this mean something ?
Thanks,
Leela sankar
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