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feat: add std fallback #37

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Feb 24, 2024
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9 changes: 5 additions & 4 deletions .github/workflows/ci.yml
Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@ jobs:
strategy:
matrix:
os: [macos-latest, ubuntu-latest, windows-latest]
features: ["atomic", "atomic,fallback-coarse"]
rust: [stable]
env:
RUST_BACKTRACE: 1
Expand All @@ -29,13 +30,13 @@ jobs:
- name: Check format
run: cargo fmt --all -- --check
- name: Build
run: cargo build --workspace --all-targets --all-features
run: cargo build --workspace --all-targets --features ${{ matrix.features }}
- name: Clippy
run: cargo clippy --workspace --all-targets --all-features -- -D warnings
run: cargo clippy --workspace --all-targets --features ${{ matrix.features }} -- -D warnings
- name: Run tests
run: cargo test --workspace --all-targets --all-features -- --nocapture
run: cargo test --workspace --all-targets --features ${{ matrix.features }} -- --nocapture
- name: Run benches
run: cargo bench --workspace --all-targets --all-features
run: cargo bench --workspace --all-targets --features ${{ matrix.features }}

build-wasm:
runs-on: ubuntu-latest
Expand Down
5 changes: 3 additions & 2 deletions Cargo.toml
Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
[package]
name = "minstant"
version = "0.1.6"
version = "0.1.7"
authors = ["The TiKV Authors"]
edition = "2021"
license = "MIT"
Expand All @@ -16,11 +16,12 @@ rustdoc-args = ["--cfg", "docsrs"]

[dependencies]
ctor = "0.1.20"
coarsetime = "0.1"
coarsetime = { version = "0.1", optional = true }
web-time = "1.0"

[features]
atomic = []
fallback-coarse = ["coarsetime"]

[dev-dependencies]
criterion = "0.3"
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9 changes: 8 additions & 1 deletion README.md
Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,14 @@ This library is used by a high performance tracing library [`minitrace-rust`](ht

## Platform Support

Currently, only the Linux on `x86` or `x86_64` is backed by [TSC](https://en.wikipedia.org/wiki/Time_Stamp_Counter). On other platforms, `minstant` falls back to coarse time. If TSC is unstable, it will also fall back to coarse time.
Currently, only the Linux on `x86` or `x86_64` is backed by [TSC](https://en.wikipedia.org/wiki/Time_Stamp_Counter). On other platforms, `minstant` falls back to `std::time`. If TSC is unstable, it will also fall back to `std::time`.

If speed is privileged over accuracy when fallback occurs, you can use `fallback-corase` feature to use corase time:

```toml
[dependencies]
minstant = { version = "0.1", features = ["fallback-coarse"] }
```

## Benchmark

Expand Down
3 changes: 3 additions & 0 deletions src/instant.rs
Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,9 @@ use web_time::{SystemTime, UNIX_EPOCH};
pub struct Instant(u64);

impl Instant {
/// A default `Instant` that can be seen as a fixed but random moment.
pub const ZERO: Instant = Instant(0);

#[inline]
/// Returns an instant corresponding to "now".
///
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23 changes: 16 additions & 7 deletions src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -60,25 +60,34 @@ pub fn is_tsc_available() -> bool {

#[inline]
pub(crate) fn current_cycle() -> u64 {
let coarse_cycle = || {
let coarse = coarsetime::Instant::now_without_cache_update();
coarsetime::Duration::from_ticks(coarse.as_ticks()).as_nanos()
};

#[cfg(all(target_os = "linux", any(target_arch = "x86", target_arch = "x86_64")))]
{
if tsc_now::is_tsc_available() {
tsc_now::current_cycle()
} else {
coarse_cycle()
current_cycle_fallback()
}
}
#[cfg(not(all(target_os = "linux", any(target_arch = "x86", target_arch = "x86_64"))))]
{
coarse_cycle()
current_cycle_fallback()
}
}

#[cfg(not(feature = "fallback-coarse"))]
pub(crate) fn current_cycle_fallback() -> u64 {
web_time::SystemTime::now()
.duration_since(web_time::UNIX_EPOCH)
.map(|d| d.as_nanos() as u64)
.unwrap_or(0)
}

#[cfg(feature = "fallback-coarse")]
pub(crate) fn current_cycle_fallback() -> u64 {
let coarse = coarsetime::Instant::now_without_cache_update();
coarsetime::Duration::from_ticks(coarse.as_ticks()).as_nanos()
}

#[inline]
pub(crate) fn nanos_per_cycle() -> f64 {
#[cfg(all(target_os = "linux", any(target_arch = "x86", target_arch = "x86_64")))]
Expand Down
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