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remove opportunistic poll, it seems slightly beneficial for perf

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esp before I remembered to configure pipelining, the unpipelined
configuration achieved ~10% higher tput.

In any way, makes sense to not do the opportunisitc polling because
it registers the wrong waker.
This commit is contained in:
Christian Schwarz
2025-01-15 19:16:55 +01:00
parent 9b9479881a
commit 40470c66cd
1 changed files with 6 additions and 6 deletions
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12
pageserver/src/tenant/storage_layer.rs
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@@ -28,7 +28,6 @@ use std::ops::Range;
use std::pin::Pin;
use std::sync::atomic::AtomicUsize;
use std::sync::Arc;
use std::task::Poll;
use std::time::{Duration, SystemTime, UNIX_EPOCH};
use tokio_util::sync::CancellationToken;
use tracing::{trace, Instrument};
@@ -351,11 +350,12 @@ impl IoConcurrency {
match self {
IoConcurrency::Serial => fut.await,
IoConcurrency::FuturesUnordered { ios_tx, .. } => {
let mut fut = Box::pin(fut.log_if_slow("spawned_io", Duration::from_secs(1)));
// opportunistic poll to give some boost (unproven if it helps, but sounds like a good idea)
if let Poll::Ready(()) = futures::poll!(&mut fut) {
return;
}
let fut = Box::pin(fut.log_if_slow("spawned_io", Duration::from_secs(1)));
// NB: experiments showed that doing an opportunistic poll of `fut` here was bad for throughput
// while insignificant for latency.
// It would make sense to revisit the tokio-epoll-uring API in the future such that we can try
// a submission here, but never poll the future. That way, io_uring can make proccess while
// the future sits in the ios_tx queue.
match ios_tx.send(fut) {
Ok(()) => {}
Err(_) => {