Christian Schwarz bfba5e3aca page_cache: ensure forward progress on miss (#5482) ...

Problem
=======

Prior to this PR, when we had a cache miss, we'd get back a write guard,
fill it, the drop it and retry the read from cache.

If there's severe contention for the cache, it could happen that the
just-filled data gets evicted before our retry, resulting in lost work
and no forward progress.

Solution
========

This PR leverages the now-available `tokio::sync::RwLockWriteGuard`'s
`downgrade()` functionality to turn the filled slot write guard into a
read guard.
We don't drop the guard at any point, so, forward progress is ensured.


Refs
====

Stacked atop https://github.com/neondatabase/neon/pull/5480 

part of https://github.com/neondatabase/neon/issues/4743
specifically part of https://github.com/neondatabase/neon/issues/5479

2023-10-06 13:41:13 +01:00

..

benches

fix: replace all std::PathBufs with camino::Utf8PathBuf (#5352)

2023-10-04 17:52:23 +03:00

ctl

fix: replace all std::PathBufs with camino::Utf8PathBuf (#5352)

2023-10-04 17:52:23 +03:00

fixtures

walredo: simple tests and bench updates (#3045)

2023-01-16 18:24:45 +02:00

src

page_cache: ensure forward progress on miss (#5482)

2023-10-06 13:41:13 +01:00

Cargo.toml

fix: replace all std::PathBufs with camino::Utf8PathBuf (#5352)

2023-10-04 17:52:23 +03:00