Add monotonic clock calibration handling if clock speed is not found

[otherscase]

Currently, monotonic clock initialization relies on the model name field from /proc/cpuinfo to retrieve the clock speed. However, this is not always present. In case it is not present, measure the clock tick and use it instead.

Before fix:

monotonic: x86 linux, unable to determine clock rate

After fix:

21695:M 25 Oct 2025 20:16:23.168 * monotonic clock: X86 TSC @ 2649 ticks/us

Fixes #2774

[ranshid]

LGTM. I wonder if we should run multiple loops and take the minimum to reduce the chance of introducing impact caused by jitter? (eg https://elixir.bootlin.com/linux/v6.17.5/source/arch/x86/kernel/tsc.c#L758)

[otherscase]

Thanks for taking a look. Based on my quick test, running 1000+ loops seem to see 0.04% deviation at max (1 tick deviation). We could add a loop with possibly smaller measurement window and take a max out of it but not sure if that yields to practical difference. Let me know what you think.

[ranshid]

I have less knowledge of how important that is in different cloud platforms. maybe @JimB123 has some inputs based on his prior investigations.
The change LGTM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.50%. Comparing base (861d079) to head (f5be583).

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable    #2776      +/-   ##
============================================
+ Coverage     72.43%   72.50%   +0.06%     
============================================
  Files           128      128              
  Lines         70145    70145              
============================================
+ Hits          50813    50860      +47     
+ Misses        19332    19285      -47     

Files with missing lines	Coverage Δ
src/monotonic.c	100.00% <ø> (ø)

... and 12 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.