On Mon, Feb 7, 2022 at 7:03 AM Patrick Steinhardt [off-list ref] wrote:

Benchmarks in a repository with about 2,1 million refs and an up-to-date
commit-graph show a 20% speedup when mirror-fetching:

    Benchmark 1: git fetch --atomic +refs/*:refs/* (v2.35.0)
      Time (mean ± σ):     75.264 s ±  1.115 s    [User: 68.199 s, System: 10.094 s]
      Range (min … max):   74.145 s … 76.862 s    5 runs

    Benchmark 2: git fetch --atomic +refs/*:refs/* (HEAD)
      Time (mean ± σ):     62.350 s ±  0.854 s    [User: 55.412 s, System: 9.976 s]
      Range (min … max):   61.224 s … 63.216 s    5 runs

    Summary
      'git fetch --atomic +refs/*:refs/* (HEAD)' ran
        1.21 ± 0.02 times faster than 'git fetch --atomic +refs/*:refs/* (v2.35.0)'

The commit message and code make sense to me, but I wonder if there is
a reason why --atomic is used when fetching.