Created
August 14, 2025 05:58
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Slow down a process using ptrace
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| use anyhow::Result; | |
| use nix::sys::ptrace::Options; | |
| use nix::sys::wait::{Id, WaitPidFlag}; | |
| use nix::sys::{ptrace, wait}; | |
| use nix::unistd::Pid; | |
| use std::thread; | |
| use std::time::{Duration, Instant}; | |
| use sysinfo::System; | |
| fn wait_stopped(pid: Pid) -> Result<()> { | |
| wait::waitid(Id::Pid(pid), WaitPidFlag::WSTOPPED)?; | |
| Ok(()) | |
| } | |
| fn pause_for(pid: Pid, d: Duration) -> Result<()> { | |
| ptrace::interrupt(pid)?; | |
| wait_stopped(pid)?; | |
| thread::sleep(d); | |
| Ok(()) | |
| } | |
| fn unpause_for(pid: Pid, d: Duration) -> Result<()> { | |
| ptrace::cont(pid, None)?; | |
| thread::sleep(d); | |
| Ok(()) | |
| } | |
| fn slowdown_pid( | |
| pid: Pid, | |
| throttle_duration: Duration, | |
| free_duration: Duration, | |
| total_duration: Duration, | |
| ) -> Result<()> { | |
| let now = Instant::now(); | |
| let deadline = now + total_duration; | |
| ptrace::seize(pid, Options::empty())?; | |
| while Instant::now() < deadline { | |
| let diff = (deadline - Instant::now()).as_secs(); | |
| println!("[task-{pid}] throttle remaining: {diff}s",); | |
| pause_for(pid, throttle_duration)?; | |
| unpause_for(pid, free_duration)?; | |
| } | |
| ptrace::interrupt(pid)?; | |
| wait_stopped(pid)?; | |
| ptrace::detach(pid, None)?; | |
| Ok(()) | |
| } | |
| fn main() -> Result<()> { | |
| let throttle_duration = Duration::from_millis(900); | |
| let free_duration = Duration::from_millis(300); | |
| let total_duration = Duration::from_secs(100); | |
| let mut threads = Vec::new(); | |
| let sys = System::new_all(); | |
| for process in sys.processes_by_name("dragonfly".as_ref()) { | |
| if let Some(tasks) = process.tasks() { | |
| for task in tasks { | |
| let pid = task.as_u32() as i32; | |
| let t = throttle_duration; | |
| let f = free_duration; | |
| let tot = total_duration; | |
| threads.push(thread::spawn(move || { | |
| if let Err(error) = slowdown_pid(Pid::from_raw(pid), t, f, tot) { | |
| println!("failed with {error}"); | |
| } | |
| })); | |
| } | |
| } | |
| } | |
| for t in threads { | |
| t.join().unwrap(); | |
| } | |
| Ok(()) | |
| } |
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