This commit alters the `query` function in the dep graph module to preallocate
memory using `with_capacity` instead of relying on automatic growth. Discovered
in #44576 it was found that for the syntex_syntax clean incremental benchmark
the peak memory usage was found when the dep graph was being saved, particularly
the `DepGraphQuery` data structure itself. PRs like #44142 which add more
queries end up just making this much larger!
I didn't see an immediately obvious way to reduce the size of the
`DepGraphQuery` object, but it turns out that `with_capacity` helps quite a bit!
Locally 831 MB was used [before] this commit, and 770 MB is in use at the peak
of the compiler [after] this commit. That's a nice 7.5% improvement! This won't
quite make up for the losses in #44142 but I figured it's a good start.
[before]: https://gist.github.com/alexcrichton/
2d2b9c7a65503761925c5a0bcfeb0d1e
[before]: https://gist.github.com/alexcrichton/
6da51f2a6184bfb81694cc44f06deb5b
pub fn new(nodes: &[DepNode],
edges: &[(DepNode, DepNode)])
-> DepGraphQuery {
- let mut graph = Graph::new();
+ let mut graph = Graph::with_capacity(nodes.len(), edges.len());
let mut indices = FxHashMap();
for node in nodes {
- indices.insert(node.clone(), graph.next_node_index());
- graph.add_node(node.clone());
+ indices.insert(node.clone(), graph.add_node(node.clone()));
}
for &(ref source, ref target) in edges {
}
}
+ pub fn with_capacity(nodes: usize, edges: usize) -> Graph<N, E> {
+ Graph {
+ nodes: SnapshotVec::with_capacity(nodes),
+ edges: SnapshotVec::with_capacity(edges),
+ }
+ }
+
// # Simple accessors
#[inline]
}
}
+ pub fn with_capacity(n: usize) -> SnapshotVec<D> {
+ SnapshotVec {
+ values: Vec::with_capacity(n),
+ undo_log: Vec::new(),
+ }
+ }
+
fn in_snapshot(&self) -> bool {
!self.undo_log.is_empty()
}