rdtsc(9)

💅 rdtsc — kernel API manual, bestie edition ✨

Okay so welcome to the Kernel API Manual entry for rdtsc, and honestly? She's a little chaotic but she's iconic. Buckle up 🎀

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🌸 NAME 🌸

rdtsc — returns the current TSC without ordering constraints

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⭐ SYNOPSIS ⭐

u64 rdtsc (void );

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🦋 ARGUMENTS 🦋

• void — no arguments. none. zero. nada. she takes nothing and she gives you a u64, main character energy fr 💅

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🔥 DESCRIPTION 🔥

So rdtsc returns the result of RDTSC as a 64-bit integer. That's it, that's the vibe ✨

The only ordering constraint it supplies is the ordering implied by "asm volatile" — which means it will put the RDTSC in the place you expect. Lowkey the bare minimum, but she delivers 🫶

⚠️ but here's the tea: the CPU can and will speculatively execute that RDTSC, though. so the results can be non-monotonic if you compare them on different CPUs. not me getting different numbers on different cores 😭💀 plan accordingly bestie, this is NOT a globally-consistent-clock situation, no cap.

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👑 SEE ALSO 👑

• Kernel file ./arch/x86/include/asm/tsc.h
• rdtsc_ordered(9) — the ordered one, iykyk 🌈

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that's the whole page, mwah 💖 sourced straight from ./arch/x86/include/asm, dated October 2026, and filed under rdtsc(9). go forth and timestamp responsibly, bestie 🧚‍♀️🍓