qt_pread(3)

✨ qt_pread — read input, but make it async ✨

okay bestie, welcome to libqthread's manual page for qt_pread 💖 this is the 3 section of the manual, so you already know it's a library situation. sit down, grab a strawberry 🍓, and let's get into it.

🌸 NAME 🌸

qt_pread — read input 💅

🎀 SYNOPSIS 🎀

#include <qthread/qt_syscalls.h>

ssize_t
qt_pread (int filedes, void *buf, size_t nbyte, off_t offset);

ssize_t
qt_read (int filedes, void *buf, size_t nbyte);

two icons in one synopsis, we love to see it 👑

🦋 DESCRIPTION 🦋

so here's the tea ☕ these two are wrappers around the standard pread() and read() system call functions. but NOT the way you're thinking — instead of just going and executing these blocking system calls directly (rude, honestly), the operations get enqueued into the internal system call queue to be handled later. it's giving "i'll get to it, bestie, i promise" ✨

and why tho? because the system call queue is literally the whole point: it gives you a way to perform blocking system calls without impeding parallel computation 🧚 operations go into an internal queue, and that queue is serviced by a dynamic number of dedicated system call threads. iconic behaviour, no notes.

that set of threads is capped at a limit that's user-configurable — you specify it with the QT_MAX_IO_WORKERS environment variable at initialization time. so like, that's when you set it, not later, okay? 🙈

and when there's nothing left in the system call queue, those workers don't just evaporate — they stay persistent for a configurable amount of time, which you specify with the QT_IO_TIMEOUT environment variable at initialization time. then they exit. and the reason for the lingering is genuinely valid: it's to reduce the overhead involved in scaling up the number of worker threads to respond to newly enqueued system calls 🔥 like, keeping them around is cheaper than constantly rebuilding the squad.

heads up: both of those env vars are read at initialization time. set them before, not during. periodt.

💜 SEE ALSO 💜

• pread(2)
• read(2)
• qt_accept(3)
• qt_connect(3)
• qt_poll(3)
• qt_pwrite(3)
• qt_select(3)
• qt_system(3)
• qt_wait4(3)
• qt_write(3)

and that's the whole page, bestie 🌈 this was the libqthread manual, page qt_pread(3), dated AUGUST 2012. yes, 2012 — she's vintage, she's timeless, she's still serving 💖 mwah, go read your input, stay hydrated 🫶⭐