cpucycles(3)

💅 cpucycles — count CPU cycles ✨

okay bestie so this is cpucycles(3) from the Library Functions Manual, and it's literally the vibe check for how many clock cycles your CPU has been through. sit down, grab a boba, we're doing this 🧋

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🌸 NAME 🌸

cpucycles — count CPU cycles, fr fr 💖

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✨ SYNOPSIS ✨

#include <cpucycles.h>

long long count = cpucycles();
long long persecond = cpucycles_persecond();
const char *implementation = cpucycles_implementation();
const char *version = cpucycles_version();

Link with -lcpucycles. Old systems may also need -lrt. (yes queen, the old ones need extra support, we don't judge 👑)

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🦋 DESCRIPTION 🦋

cpucycles() returns an estimate for the number of CPU cycles that have occurred since an unspecified time in the past (perhaps system boot, perhaps program startup). it's giving "somewhere in the past, don't worry about it" 😌

Accessing true cycle counters can be difficult on some CPUs and operating systems. cpucycles() does its best to produce accurate results, but selects a low-precision counter if the only other option is failure. so like, she tries her hardest, but if the only alternative is crashing out 💀 she'll take the lower-precision counter. that's called self-care.

cpucycles_persecond() returns an estimate for the number of CPU cycles per second. This estimate comes from /etc/cpucyclespersecond if that file exists, otherwise from various OS mechanisms, otherwise from the cpucyclespersecond environment variable if that is set, otherwise 2399987654. it's a whole pipeline bestie — file first, then the OS doing its thing, then the env var, then just the iconic fallback number 2399987654 🎀

cpucycles_implementation() returns the name of the counter in use: e.g., "amd64-perfpmc". name drop, periodt 💅

cpucycles_version() returns the libcpucycles version number as a string: e.g., "20260625". Results of cpucycles_implementation() should be interpreted relative to cpucycles_version(). so like, always read those two together, they're a matched set, they're soulmates 🫶

cpucycles is actually a function pointer. The first call to cpucycles() or cpucycles_persecond() or cpucycles_implementation() selects one of the available counters and updates the cpucycles pointer accordingly. Subsequent calls to cpucycles() are thread-safe. so the very first call is the main character who picks the counter, and after that everybody's safe to run around concurrently 🔥

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👀 SEE ALSO 👀

• gettimeofday(2)
• clock_gettime(2)

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okay that's it, that's the page, you ate this one bestie 🌈💜 this was cpucycles(3) — no fancy version line or date on the footer, it's just sitting there being iconic, exactly as printed: cpucycles(3) ✨