https://bugs.dpdk.org/show_bug.cgi?id=959
Bug ID: 959
Summary: tsc hz not matching kernel reported tcs frequency
Product: DPDK
Version: 21.11
Hardware: x86
OS: Linux
Status: UNCONFIRMED
Severity: normal
Priority: Normal
Component: core
Assignee: dev@dpdk.org
Reporter: maria.lingem...@ericsson.com
Target Milestone: ---
On some machines the dpdk value of tsc hz does not match the kernel value.
The effect of this can be observed by writing a small test program that
measures elapsed time using two different sources.
The issue has been shown by taking clock_gettime() and rte_get_tsc_cycles(),
sleep, and then fetch the time stamps again with clock_gettime() and
rte_get_tsc_cycles().
When calculating the time from the two sources we notice a difference of ~2.3
ms per second.
Example from a test run with 1 second sleep:
rte_get_tsc_hz=2400000000
clock_gettime=1000056 us, tsc_time=997708 us, diff=2348 us
Info from dmesg:
tsc: Refined TSC clocksource calibration: 2394.365 MHz
We don't see the time difference on
Intel(R) Xeon(R) CPU E5-2680 v4 @ 2.40GHz
Linux kernel 4.13.0-16-generic
but we do observe it on
Intel(R) Xeon(R) Gold 6148 CPU @ 2.40GHz
Linux kernel 5.4.0-100-generic
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