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uv-resolver: fix perf regression

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We significantly regressed performance in some cases because we were
cloning the resolver state one more time than we needed to. That doesn't
sound like a lot, but in the case where there are no forks, it implies
we were cloning the state for every `get_dependencies` called when we
shouldn't have been cloning it at all.

Avoiding the clone results in somewhat tortured code. This can probably
be refactored by moving bits out to a helper routine, but that also
seemed non-trivial. So we let this suffice for now.
This commit is contained in:
Andrew Gallant 2024-05-30 11:41:49 -04:00 • committed by Andrew Gallant
parent 17c043536b
commit d3b7d800ea
1 changed files with 26 additions and 7 deletions
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33
crates/uv-resolver/src/resolver/mod.rs
View file

@ -464,15 +464,26 @@ impl<InstalledPackages: InstalledPackagesProvider> ResolverState<InstalledPackag
.insert(version.clone())
{
// Retrieve that package dependencies.
let package = &state.next;
let package = state.next.clone();
let forks = self.get_dependencies_forking(
package,
&package,
&version,
&mut state.priorities,
&request_sink,
)?;
for fork in forks {
let mut state = state.clone();
let forks_len = forks.len();
// This is a somewhat tortured technique to ensure
// that our resolver state is only cloned as much
// as it needs to be. And *especially*, in the case
// when no forks occur, the state should not be
// cloned at all. We basically move the state into
// `forked_states`, and then only clone it if there
// it at least one more fork to visit.
let mut cur_state = Some(state);
for (i, fork) in forks.into_iter().enumerate() {
let is_last = i == forks_len - 1;
let state = cur_state.as_mut().unwrap();
// let mut state = state.clone();
let dependencies = match fork {
Dependencies::Unavailable(reason) => {
state
@ -482,13 +493,17 @@ impl<InstalledPackages: InstalledPackagesProvider> ResolverState<InstalledPackag
version.clone(),
UnavailableReason::Version(reason),
));
forked_states.push(state);
let forked_state = cur_state.take().unwrap();
if !is_last {
cur_state = Some(forked_state.clone());
}
forked_states.push(forked_state);
continue;
}
Dependencies::Available(constraints)
if constraints
.iter()
.any(|(dependency, _)| dependency == package) =>
.any(|(dependency, _)| dependency == &package) =>
{
if enabled!(Level::DEBUG) {
prefetcher.log_tried_versions();
@ -515,7 +530,11 @@ impl<InstalledPackages: InstalledPackagesProvider> ResolverState<InstalledPackag
dep_incompats,
&state.pubgrub.incompatibility_store,
);
forked_states.push(state);
let forked_state = cur_state.take().unwrap();
if !is_last {
cur_state = Some(forked_state.clone());
}
forked_states.push(forked_state);
}
continue 'FORK;
}