From 1b6a04ca5504955c571d1c97504fb45ea0befee4 Mon Sep 17 00:00:00 2001 From: Valentin Popov Date: Mon, 8 Jan 2024 01:21:28 +0400 Subject: Initial vendor packages Signed-off-by: Valentin Popov --- vendor/rayon-core/src/sleep/counters.rs | 277 ++++++++++++++++++++++++++++++++ 1 file changed, 277 insertions(+) create mode 100644 vendor/rayon-core/src/sleep/counters.rs (limited to 'vendor/rayon-core/src/sleep/counters.rs') diff --git a/vendor/rayon-core/src/sleep/counters.rs b/vendor/rayon-core/src/sleep/counters.rs new file mode 100644 index 0000000..53d2c55 --- /dev/null +++ b/vendor/rayon-core/src/sleep/counters.rs @@ -0,0 +1,277 @@ +use std::sync::atomic::{AtomicUsize, Ordering}; + +pub(super) struct AtomicCounters { + /// Packs together a number of counters. The counters are ordered as + /// follows, from least to most significant bits (here, we assuming + /// that [`THREADS_BITS`] is equal to 10): + /// + /// * Bits 0..10: Stores the number of **sleeping threads** + /// * Bits 10..20: Stores the number of **inactive threads** + /// * Bits 20..: Stores the **job event counter** (JEC) + /// + /// This uses 10 bits ([`THREADS_BITS`]) to encode the number of threads. Note + /// that the total number of bits (and hence the number of bits used for the + /// JEC) will depend on whether we are using a 32- or 64-bit architecture. + value: AtomicUsize, +} + +#[derive(Copy, Clone)] +pub(super) struct Counters { + word: usize, +} + +/// A value read from the **Jobs Event Counter**. +/// See the [`README.md`](README.md) for more +/// coverage of how the jobs event counter works. +#[derive(Copy, Clone, Debug, PartialEq, PartialOrd)] +pub(super) struct JobsEventCounter(usize); + +impl JobsEventCounter { + pub(super) const DUMMY: JobsEventCounter = JobsEventCounter(std::usize::MAX); + + #[inline] + pub(super) fn as_usize(self) -> usize { + self.0 + } + + /// The JEC "is sleepy" if the last thread to increment it was in the + /// process of becoming sleepy. This is indicated by its value being *even*. + /// When new jobs are posted, they check if the JEC is sleepy, and if so + /// they incremented it. + #[inline] + pub(super) fn is_sleepy(self) -> bool { + (self.as_usize() & 1) == 0 + } + + /// The JEC "is active" if the last thread to increment it was posting new + /// work. This is indicated by its value being *odd*. When threads get + /// sleepy, they will check if the JEC is active, and increment it. + #[inline] + pub(super) fn is_active(self) -> bool { + !self.is_sleepy() + } +} + +/// Number of bits used for the thread counters. +#[cfg(target_pointer_width = "64")] +const THREADS_BITS: usize = 16; + +#[cfg(target_pointer_width = "32")] +const THREADS_BITS: usize = 8; + +/// Bits to shift to select the sleeping threads +/// (used with `select_bits`). +#[allow(clippy::erasing_op)] +const SLEEPING_SHIFT: usize = 0 * THREADS_BITS; + +/// Bits to shift to select the inactive threads +/// (used with `select_bits`). +#[allow(clippy::identity_op)] +const INACTIVE_SHIFT: usize = 1 * THREADS_BITS; + +/// Bits to shift to select the JEC +/// (use JOBS_BITS). +const JEC_SHIFT: usize = 2 * THREADS_BITS; + +/// Max value for the thread counters. +pub(crate) const THREADS_MAX: usize = (1 << THREADS_BITS) - 1; + +/// Constant that can be added to add one sleeping thread. +const ONE_SLEEPING: usize = 1; + +/// Constant that can be added to add one inactive thread. +/// An inactive thread is either idle, sleepy, or sleeping. +const ONE_INACTIVE: usize = 1 << INACTIVE_SHIFT; + +/// Constant that can be added to add one to the JEC. +const ONE_JEC: usize = 1 << JEC_SHIFT; + +impl AtomicCounters { + #[inline] + pub(super) fn new() -> AtomicCounters { + AtomicCounters { + value: AtomicUsize::new(0), + } + } + + /// Load and return the current value of the various counters. + /// This value can then be given to other method which will + /// attempt to update the counters via compare-and-swap. + #[inline] + pub(super) fn load(&self, ordering: Ordering) -> Counters { + Counters::new(self.value.load(ordering)) + } + + #[inline] + fn try_exchange(&self, old_value: Counters, new_value: Counters, ordering: Ordering) -> bool { + self.value + .compare_exchange(old_value.word, new_value.word, ordering, Ordering::Relaxed) + .is_ok() + } + + /// Adds an inactive thread. This cannot fail. + /// + /// This should be invoked when a thread enters its idle loop looking + /// for work. It is decremented when work is found. Note that it is + /// not decremented if the thread transitions from idle to sleepy or sleeping; + /// so the number of inactive threads is always greater-than-or-equal + /// to the number of sleeping threads. + #[inline] + pub(super) fn add_inactive_thread(&self) { + self.value.fetch_add(ONE_INACTIVE, Ordering::SeqCst); + } + + /// Increments the jobs event counter if `increment_when`, when applied to + /// the current value, is true. Used to toggle the JEC from even (sleepy) to + /// odd (active) or vice versa. Returns the final value of the counters, for + /// which `increment_when` is guaranteed to return false. + pub(super) fn increment_jobs_event_counter_if( + &self, + increment_when: impl Fn(JobsEventCounter) -> bool, + ) -> Counters { + loop { + let old_value = self.load(Ordering::SeqCst); + if increment_when(old_value.jobs_counter()) { + let new_value = old_value.increment_jobs_counter(); + if self.try_exchange(old_value, new_value, Ordering::SeqCst) { + return new_value; + } + } else { + return old_value; + } + } + } + + /// Subtracts an inactive thread. This cannot fail. It is invoked + /// when a thread finds work and hence becomes active. It returns the + /// number of sleeping threads to wake up (if any). + /// + /// See `add_inactive_thread`. + #[inline] + pub(super) fn sub_inactive_thread(&self) -> usize { + let old_value = Counters::new(self.value.fetch_sub(ONE_INACTIVE, Ordering::SeqCst)); + debug_assert!( + old_value.inactive_threads() > 0, + "sub_inactive_thread: old_value {:?} has no inactive threads", + old_value, + ); + debug_assert!( + old_value.sleeping_threads() <= old_value.inactive_threads(), + "sub_inactive_thread: old_value {:?} had {} sleeping threads and {} inactive threads", + old_value, + old_value.sleeping_threads(), + old_value.inactive_threads(), + ); + + // Current heuristic: whenever an inactive thread goes away, if + // there are any sleeping threads, wake 'em up. + let sleeping_threads = old_value.sleeping_threads(); + std::cmp::min(sleeping_threads, 2) + } + + /// Subtracts a sleeping thread. This cannot fail, but it is only + /// safe to do if you you know the number of sleeping threads is + /// non-zero (i.e., because you have just awoken a sleeping + /// thread). + #[inline] + pub(super) fn sub_sleeping_thread(&self) { + let old_value = Counters::new(self.value.fetch_sub(ONE_SLEEPING, Ordering::SeqCst)); + debug_assert!( + old_value.sleeping_threads() > 0, + "sub_sleeping_thread: old_value {:?} had no sleeping threads", + old_value, + ); + debug_assert!( + old_value.sleeping_threads() <= old_value.inactive_threads(), + "sub_sleeping_thread: old_value {:?} had {} sleeping threads and {} inactive threads", + old_value, + old_value.sleeping_threads(), + old_value.inactive_threads(), + ); + } + + #[inline] + pub(super) fn try_add_sleeping_thread(&self, old_value: Counters) -> bool { + debug_assert!( + old_value.inactive_threads() > 0, + "try_add_sleeping_thread: old_value {:?} has no inactive threads", + old_value, + ); + debug_assert!( + old_value.sleeping_threads() < THREADS_MAX, + "try_add_sleeping_thread: old_value {:?} has too many sleeping threads", + old_value, + ); + + let mut new_value = old_value; + new_value.word += ONE_SLEEPING; + + self.try_exchange(old_value, new_value, Ordering::SeqCst) + } +} + +#[inline] +fn select_thread(word: usize, shift: usize) -> usize { + (word >> shift) & THREADS_MAX +} + +#[inline] +fn select_jec(word: usize) -> usize { + word >> JEC_SHIFT +} + +impl Counters { + #[inline] + fn new(word: usize) -> Counters { + Counters { word } + } + + #[inline] + fn increment_jobs_counter(self) -> Counters { + // We can freely add to JEC because it occupies the most significant bits. + // Thus it doesn't overflow into the other counters, just wraps itself. + Counters { + word: self.word.wrapping_add(ONE_JEC), + } + } + + #[inline] + pub(super) fn jobs_counter(self) -> JobsEventCounter { + JobsEventCounter(select_jec(self.word)) + } + + /// The number of threads that are not actively + /// executing work. They may be idle, sleepy, or asleep. + #[inline] + pub(super) fn inactive_threads(self) -> usize { + select_thread(self.word, INACTIVE_SHIFT) + } + + #[inline] + pub(super) fn awake_but_idle_threads(self) -> usize { + debug_assert!( + self.sleeping_threads() <= self.inactive_threads(), + "sleeping threads: {} > raw idle threads {}", + self.sleeping_threads(), + self.inactive_threads() + ); + self.inactive_threads() - self.sleeping_threads() + } + + #[inline] + pub(super) fn sleeping_threads(self) -> usize { + select_thread(self.word, SLEEPING_SHIFT) + } +} + +impl std::fmt::Debug for Counters { + fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { + let word = format!("{:016x}", self.word); + fmt.debug_struct("Counters") + .field("word", &word) + .field("jobs", &self.jobs_counter().0) + .field("inactive", &self.inactive_threads()) + .field("sleeping", &self.sleeping_threads()) + .finish() + } +} -- cgit v1.2.3