Mercurial > hg
diff rust/hg-core/Cargo.toml @ 48950:11c0411bf4e2
dirstate-tree: optimize HashMap lookups with raw_entry_mut
This switches to using `HashMap` from the hashbrown crate,
in order to use its `raw_entry_mut` method.
The standard library’s `HashMap` is also based on this same crate,
but `raw_entry_mut` is not yet stable there:
https://github.com/rust-lang/rust/issues/56167
Using version 0.9 because 0.10 is yanked and 0.11 requires Rust 1.49
This replaces in `DirstateMap::get_or_insert_node` a call to
`HashMap<K, V>::entry` with `K = WithBasename<Cow<'on_disk, HgPath>>`.
`entry` takes and consumes an "owned" `key: K` parameter, in case a new entry
ends up inserted. This key is converted by `to_cow` from a value that borrows
the `'path` lifetime.
When this function is called by `Dirstate::new_v1`, `'path` is in fact
the same as `'on_disk` so `to_cow` can return an owned key that contains
`Cow::Borrowed`.
For other callers, `to_cow` needs to create a `Cow::Owned` and thus make
a costly heap memory allocation. This is wasteful if this key was already
present in the map. Even when inserting a new node this is typically the case
for its ancestor nodes (assuming most directories have numerous descendants).
Differential Revision: https://phab.mercurial-scm.org/D12317
author | Simon Sapin <simon.sapin@octobus.net> |
---|---|
date | Tue, 08 Feb 2022 15:51:52 +0100 |
parents | 0dc698c91ca0 |
children | ec8d9b5a5e7c |
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--- a/rust/hg-core/Cargo.toml Fri Mar 04 13:33:55 2022 +0100 +++ b/rust/hg-core/Cargo.toml Tue Feb 08 15:51:52 2022 +0100 @@ -13,6 +13,7 @@ bytes-cast = "0.2" byteorder = "1.3.4" derive_more = "0.99" +hashbrown = {version = "0.9.1", features = ["rayon"]} home = "0.5" im-rc = "15.0.*" itertools = "0.9"