System::refresh_processes() doesn't update CPU

[M1loseph]

My setup

OS: WSL, Ubuntu 24.04 LTS
Architecture: x86_64
Rust: 1.81.0
Sysinfo: 0.31.4

Issue

When I call System::refresh_processes_specifics(ProcessesToUpdate::Some(&[pid], ProcessRefreshKind::new().with_cpu().with_memory()) the cpu usage of provided process is not updated. Calling Process::cpu_usage() always returns the same value.

Expected behavious

CPU usage is updated and can be read from Process struct.

Actuall result

Only memory gets updated, CPU value always stays the same.

What is interesting, when I replaced ProcessesToUpdate::Some(...) with ProcessesToUpdate::All, all of a sudden it is updating correctly.

Code to reproduce issue

use std::{thread, time::Duration};

use sysinfo::{get_current_pid, ProcessRefreshKind, System};


fn main() {
    let mut system = System::new_all();
    loop {
        thread::sleep(Duration::from_secs(1));
        let pid = get_current_pid().unwrap();
        system.refresh_processes_specifics(
            sysinfo::ProcessesToUpdate::Some(&[pid]),
            ProcessRefreshKind::everything()
        );
        let process = system.process(pid).unwrap();

        println!("cpu={}, mem={}", process.cpu_usage(), process.memory());
    }
}

top -p <pid> returns CPU usage from 0.0 to 0.3, to the value should fluctuate a bit, but it always remains zero.

[M1loseph]

I even added some shitty fibbonaci function to make sure that CPU is heavily loaded - even when top returns 90% CPU utilization, I still get 0 printed to the console :(

use std::{thread, time::Duration};

use sysinfo::{get_current_pid, ProcessRefreshKind, System};


fn fib(n: u64) -> u64 {
    if n == 0 || n == 1 {
        return 1;
    }
    return fib(n - 1) + fib(n - 2);
}

fn main() {
    thread::spawn(|| {
        let calculation = fib(100);
        println!("{calculation}");
    });
    let mut system = System::new_all();
    loop {
        thread::sleep(Duration::from_secs(1));
        let pid = get_current_pid().unwrap();
        system.refresh_processes_specifics(
            sysinfo::ProcessesToUpdate::Some(&[pid]),
            ProcessRefreshKind::everything()
        );
        let process = system.process(pid).unwrap();

        println!("cpu={}, mem={}", process.cpu_usage(), process.memory());
    }
}

[GuillaumeGomez]

I'll try to take a look in the next days. Could be interesting if you checked what path the code is entering into on your side as I don't have your setup.