For large repositories, the easiest way to improve performance is to enable feature.manyFiles:

git config --global feature.manyFiles true

Enabling this configuration will enable a newer index format and make git status faster.

With core.fsmonitor, Git will use FSEvents to monitor your repository for changes in a daemon.

git config --global core.fsmonitor true

This will improve git status performance too.

Some git log commands can be sped up with fetch.writeCommitGraph, but I didn’t notice a huge change with this.

git config --global fetch.writeCommitGraph true

I don’t notice git checkout being slow, but checkout.workers is supposed to help on SSDs:

git config --global checkout.workers 0

Conclusion

Enable these settings to improve repository performance.

git config --global feature.manyFiles true
git config --global core.fsmonitor true
git config --global fetch.writeCommitGraph true
git config --global checkout.workers 0