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  • Raphaël Gomès's avatar
    rust-performance: introduce FastHashMap type alias for HashMap · 5ac243a92e37
    Raphaël Gomès authored
    Rust's default hashing is slow, because it is meant for preventing collision
    attacks.
    For all of the current Rust code, we don't care about those attacks, because
    if an person with bad intentions has write access to your repo, you have other
    issues.
    
    I've chosen to use the TwoXHash crate because it was made by a reputable member
    of the Rust community and has very good benchmarks.
    
    For now it does not seem to improve performance by much for the current code,
    but it's something else to not worry about when benchmarking code: in a
    previous experiment with copytracing in Rust, it accounted for more than 10%
    of the time of the entire script.
    
    Differential Revision: https://phab.mercurial-scm.org/D7116
    5ac243a92e37