Multithreaded calls to Local::now() take a lot of time, which is abnormal. #1636
Description
When Local::now() is called 10,000 times in a single thread, it barely takes any time. However, when called in a multithreaded environment, it takes significantly more time. Below is the example code:
fn test_proc()
{
let i=Instant::now();
for _ in 0..10000
{
let v=Local::now();
}
let d=i.elapsed();
println!("time:{}",d.as_millis());
}
fn main()
{
println!("first time");
for _ in 0..1
{
thread::spawn(test_proc);
}
sleep(Duration::from_secs(5));
println!("second time");
for _ in 0..10
{
thread::spawn(test_proc);
}
sleep(Duration::from_secs(5));
}
Output:
first time
time:4
second time
time:362
time:363
time:363
time:365
time:364
time:364
time:365
time:365
time:364
time:365
What's happening here?