STRUCT TIMECOUNTER(9)

🦋 struct timecounter(9) 🦋

okay bestie, welcome to the Kernel API Manual ✨ — yes this is that kernel, and yes this page is literally about the little struct that keeps your nanoseconds from going full chaos mode 💖

💫 NAME 💫

struct timecounter — it's the layer that sits right above a &struct cyclecounter and counts nanoseconds, periodt 🎀

It holds all the state that timecounter_read() needs so it can detect cycle counter wrap around. You set it up with timecounter_init(). It's also the thing that converts cycle counts into the matching nanosecond counts via timecounter_cyc2time() 🔥

And ngl, the fine print matters here:

• you (the user of this code, bestie, not us 🙈) are responsible for initializing the underlying cycle counter hardware
• you are responsible for the locking issues
• you are responsible for reading the time more often than the cycle counter wraps around 👑

The good news? The nanosecond counter will only wrap around after ~585 years — so like, not your problem, not your era 💀💅

🌸 SYNOPSIS 🌸

struct timecounter {
    struct cyclecounter *cc;
    u64 cycle_last;
    u64 nsec;
    u64 mask;
    u64 frac;
 };

🫶 Members 🫶

• cc — the cycle counter this instance is using, its ride-or-die 🌈
• cycle_last — the most recent cycle counter value that timecounter_read has seen 👀
• nsec — a continuously increasing count, just going up and up, main character energy ⭐
• mask — the bit mask used for maintaining the frac field 🎀
• frac — the accumulated fractional nanoseconds, the little leftovers we refuse to throw away 🍓

🧚 SEE ALSO 🧚

Kernel file ./include/linux/timecounter.h, plus the whole squad:

• struct cyclecounter(9)
• cyclecounter_cyc2ns(9)
• timecounter_adjtime(9)
• timecounter_init(9)
• timecounter_read(9)
• timecounter_cyc2time(9)

and that's the whole vibe check, bestie 💜 this page came out of ./include/linux and it's dated October 2026 — screenshot it, frame it, it's iconic ✨💅🦋