quanta
quanta is a high-speed timing library, useful for getting the current time very quickly, as well as manipulating it.
code of conduct
NOTE: All conversations and contributions to this project shall adhere to the Code of Conduct.
usage
The API documentation of this library can be found at docs.rs/quanta.
general features
- count CPU cycles via Time Stamp Counter (TSC). or
- get monotonic time, in nanoseconds, based on TSC (or OS fallback)
- extremely low overhead where possible
- mockable
- cross-platform
- fun, science-y name!
platform / architecture support
For platforms, we have tier 1 support for Linux, Windows, and macOS/iOS. Platforms such as Solaris or various BSDs have tier 2.5 support: quanta
should work on them by virtue of depending on libc
, but we don't test or build on these platforms as all.
Both x86/x86-64 and SSE2 support are checked for at compile-time, so compiler flags must be set correctly. Further checks will happen at runtime to assert that the TSC source itself is stable enough for taking measurements, and if so, will be utilized.
performance
quanta
sits neck-and-neck with native OS time facilities: the cost of Clock::now
is on par
Instant::now
from the stdlib, if not better.
why use this over stdlib?
Beyond having a performance edge in specific situations, the ability to use mocked time makes it easier to actually test that your application is doing the right thing when time is involved.
Additionally, and as mentioned in the general features section, quanta
provides a safe/thin
wrapper over accessing the Time Stamp Counter, which allows measuring cycle counts over short
sections of code. This can be relevant/important for accurately measuring performance-critical sections of code.
alternative crates
chrono
:- based on
std::time::SystemTime
: non-monotonic reads - focused on timezone-based "date/time" measurements, not intervals/elapsed time
- clock cannot be altered at all (no pause, no discrete updates)
- based on
time
:- based on
std::time::SystemTime
andstd::time::Instant
:time::Time
/time::PrimitiveDateTime
useSystemTime
: non-monotonic readstime::Instant
usesInstant
: monotonic reads
- focused on timezone-based "date/time" measurements, not interval/elapsed time
- clock cannot be altered at all (no pause, no discrete updates)
- based on
clock
:- based on
std::time::SystemTime
: non-monotonic reads - clock can be swapped (trait-based)
- no free function for acquiring time
- based on
clocksource
:- based on TSC w/ OS fallback; non-monotonic reads
- clock cannot be altered at all (no pause, no discrete updates)
- depends on unstable
asm!
macro + feature flag to enable TSC - no free function for acquiring time
pausable_clock
:- based on
std::time::Instant
: monotonic reads - clock can be paused (time can be delayed, but not discretely updated)
- no free function for acquiring time
- based on
license
quanta is licensed under the MIT license. (LICENSE or http://opensource.org/licenses/MIT)