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73fbd61bd0
`performance.timeOrigin` was being set from when JS started executing, but `op_now` measures from an `std::time::Instant` stored in `OpState`, which is created at a completely different time. This caused `performance.timeOrigin` to be very incorrect. This PR corrects the origin and also cleans up some of the timer code. Compared to `Date.now()`, `performance`'s time origin is now consistently within 5us (0.005ms) of system time. 
85 lines
2.2 KiB
Rust
85 lines
2.2 KiB
Rust
// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
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//! This module helps deno implement timers and performance APIs.
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use deno_core::op2;
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use deno_core::OpState;
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use std::time::Duration;
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use std::time::Instant;
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use std::time::SystemTime;
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use std::time::UNIX_EPOCH;
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pub trait TimersPermission {
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fn allow_hrtime(&mut self) -> bool;
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}
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impl TimersPermission for deno_permissions::PermissionsContainer {
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#[inline(always)]
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fn allow_hrtime(&mut self) -> bool {
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true
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}
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}
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pub struct StartTime(Instant);
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impl Default for StartTime {
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fn default() -> Self {
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Self(Instant::now())
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}
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}
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impl std::ops::Deref for StartTime {
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type Target = Instant;
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fn deref(&self) -> &Self::Target {
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&self.0
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}
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}
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fn expose_time<TP>(state: &mut OpState, duration: Duration, out: &mut [u8])
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where
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TP: TimersPermission + 'static,
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{
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let seconds = duration.as_secs() as u32;
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let mut subsec_nanos = duration.subsec_nanos();
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// If the permission is not enabled
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// Round the nano result on 2 milliseconds
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// see: https://developer.mozilla.org/en-US/docs/Web/API/DOMHighResTimeStamp#Reduced_time_precision
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if !state.borrow_mut::<TP>().allow_hrtime() {
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let reduced_time_precision = 2_000_000; // 2ms in nanoseconds
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subsec_nanos -= subsec_nanos % reduced_time_precision;
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}
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if out.len() >= 8 {
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out[0..4].copy_from_slice(&seconds.to_ne_bytes());
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out[4..8].copy_from_slice(&subsec_nanos.to_ne_bytes());
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}
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}
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#[op2(fast)]
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pub fn op_now<TP>(state: &mut OpState, #[buffer] buf: &mut [u8])
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where
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TP: TimersPermission + 'static,
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{
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let start_time = state.borrow::<StartTime>();
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let elapsed = start_time.elapsed();
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expose_time::<TP>(state, elapsed, buf);
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}
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#[op2(fast)]
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pub fn op_time_origin<TP>(state: &mut OpState, #[buffer] buf: &mut [u8])
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where
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TP: TimersPermission + 'static,
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{
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// https://w3c.github.io/hr-time/#dfn-estimated-monotonic-time-of-the-unix-epoch
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let wall_time = SystemTime::now();
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let monotonic_time = state.borrow::<StartTime>().elapsed();
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let epoch = wall_time.duration_since(UNIX_EPOCH).unwrap() - monotonic_time;
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expose_time::<TP>(state, epoch, buf);
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}
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#[allow(clippy::unused_async)]
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#[op2(async(lazy), fast)]
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pub async fn op_defer() {}
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