STRUCT TK_READ_BASE(9)

💖 struct tk_read_base(9) 💖

okay so this is a page from the Kernel API Manual and it's all about struct tk_read_base — literally the base structure for timekeeping readout, iykyk 🕰️✨

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🌸 NAME 🌸

struct tk_read_base — the base structure for timekeeping readout. that's it, that's the vibe 🎀

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✨ SYNOPSIS ✨

get a load of this icon:

struct tk_read_base {
    struct clocksource      *clock;
    u64 mask;
    u64 cycle_last;
    u32 mult;
    u32 shift;
    u64 xtime_nsec;
    ktime_t base;
    u64 base_real;
 };

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🦋 Members 🦋

no cap, every single field, coming right up:

• clock — the current clocksource being used for timekeeping. the main character of the time source world 👑
• mask — the bitmask for two's complement subtraction of non-64bit clocks. lowkey essential 🧮
• cycle_last — the clock cycle value at the last update. the receipts, basically 🧾
• mult — the (NTP adjusted) multiplier for scaled math conversion. yes bestie, NTP adjusted 💅
• shift — the shift value for scaled math conversion. shifting, as one does ✨
• xtime_nsec — the shifted (fractional) nano seconds offset for readout. fractional! fancy! 🍓
• base — the ktime_t (nanoseconds) base time for readout ⏱️
• base_real — the nanoseconds base value for the clock REALTIME readout. REALTIME in all caps, she means it 🔥

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🌈 Description 🌈

so this struct is 56 byte on 64 bit — and together with a seqcount it occupies a single 64byte cache line. cache line efficiency? she ate. 💀✨

the reason the struct is separate from struct timekeeper is that it's also used for the fast NMI safe accessors. multitasking queen 🫶

and base_real? that one exists specifically for the fast NMI safe accessor, so you can read clock realtime from any context. any context!! 🙈💜

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⭐ SEE ALSO ⭐

• Kernel file ./include/linux/timekeeper_internal.h
• struct timekeeper(9)

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that's the whole page bestie, go forth and read those cycles 💖🧚

🌷 source/version and date, sign-off style: this one lives in ./include/linux, dated October 2026, and the page is struct tk_read_base(9) — mwah, periodt 💅🎀