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Remove all of the dynamic control stuff for now and just use nonblocking sends + 1 second receive timeouts

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This commit is contained in:
Tyler Neely 2019-08-09 12:22:54 +02:00
parent ab613a53e5
commit 81fa1d419a
1 changed files with 10 additions and 42 deletions
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52
src/task/blocking.rs
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@ -14,9 +14,6 @@ use lazy_static::lazy_static;
use crate::utils::abort_on_panic;
const MAX_THREADS: u64 = 10_000;
const MIN_WAIT_US: u64 = 10;
const MAX_WAIT_US: u64 = 10_000;
const WAIT_SPREAD: u64 = MAX_WAIT_US - MIN_WAIT_US;
static DYNAMIC_THREAD_COUNT: AtomicU64 = AtomicU64::new(0);
@ -52,8 +49,7 @@ lazy_static! {
// Create up to MAX_THREADS dynamic blocking task worker threads.
// Dynamic threads will terminate themselves if they don't
// receive any work after a timeout that scales down as the
// total number of threads scales up.
// receive any work after one second.
fn maybe_create_another_blocking_thread() {
// We use a `Relaxed` atomic operation because
// it's just a heuristic, and would not lose correctness
@ -63,20 +59,11 @@ fn maybe_create_another_blocking_thread() {
return;
}
// We want to give up earlier when we have more threads
// to exert backpressure on the system submitting work
// to do.
let utilization_percent = (workers * 100) / MAX_THREADS;
let relative_wait_limit = (WAIT_SPREAD * utilization_percent) / 100;
// higher utilization -> lower wait time
let wait_limit_us = MAX_WAIT_US - relative_wait_limit;
assert!(wait_limit_us >= MIN_WAIT_US);
let wait_limit = Duration::from_micros(wait_limit_us);
thread::Builder::new()
.name("async-blocking-driver-dynamic".to_string())
.spawn(move || {
.spawn(|| {
let wait_limit = Duration::from_secs(1);
DYNAMIC_THREAD_COUNT.fetch_add(1, Ordering::Relaxed);
while let Ok(task) = POOL.receiver.recv_timeout(wait_limit) {
abort_on_panic(|| task.run());
@ -86,35 +73,16 @@ fn maybe_create_another_blocking_thread() {
.expect("cannot start a dynamic thread driving blocking tasks");
}
// Enqueues work, blocking on a threadpool for a certain amount of
// time based on the number of worker threads currently active in
// the system. If we cannot send our work to the pool after the
// given timeout, we will attempt to increase the number of
// worker threads active in the system, up to MAX_THREADS. The
// timeout is dynamic, and when we have more threads we block
// for longer before spinning up another thread for backpressure.
// Enqueues work, attempting to send to the threadpool in a
// nonblocking way and spinning up another worker thread if
// there is not a thread ready to accept the work.
fn schedule(t: async_task::Task<()>) {
// We use a `Relaxed` atomic operation because
// it's just a heuristic, and would not lose correctness
// even if it's random.
let workers = DYNAMIC_THREAD_COUNT.load(Ordering::Relaxed);
// We want to block for longer when we have more threads to
// exert backpressure on the system submitting work to do.
let utilization_percent = (workers * 100) / MAX_THREADS;
let relative_wait_limit = (WAIT_SPREAD * utilization_percent) / 100;
// higher utilization -> higher block time
let wait_limit_us = MIN_WAIT_US + relative_wait_limit;
assert!(wait_limit_us <= MAX_WAIT_US);
let wait_limit = Duration::from_micros(wait_limit_us);
let first_try_result = POOL.sender.send_timeout(t, wait_limit);
let first_try_result = POOL.sender.try_send(t);
match first_try_result {
Ok(()) => {
// NICEEEE
}
Err(crossbeam::channel::SendTimeoutError::Timeout(t)) => {
Err(crossbeam::channel::TrySendError::Full(t)) => {
// We were not able to send to the channel within our
// budget. Try to spin up another thread, and then
// block without a time limit on the submission of
@ -122,7 +90,7 @@ fn schedule(t: async_task::Task<()>) {
maybe_create_another_blocking_thread();
POOL.sender.send(t).unwrap()
}
Err(crossbeam::channel::SendTimeoutError::Disconnected(_)) => {
Err(crossbeam::channel::TrySendError::Disconnected(_)) => {
panic!(
"unable to send to blocking threadpool \
due to receiver disconnection"