Re: [RFC/PATCH 0/7] Rework git core for native submodules

From: Ramkumar Ramachandra <artagnon@gmail.com>
Date: Apr 7, 2013, 18:22 UTC
Message-ID: <CALkWK0nj2+PH47OhHmq89Tzi4tdwaJTKaEneAt_k2rwpWbCnuA@mail.gmail.com>
In-Reply-To: <CALkWK0n=vtPT7aFn9+T+bRxUpfXG+mYvV29YKC=_OAampQXJSA@mail.gmail.com>

Ramkumar Ramachandra wrote:

> You can't control the most fundamental thing, stat(): this is the
> primary killer of performance on a large worktree.  There is currently
> no way to block stat(): new-style submodules offers a way to configure
> which submodules to block the stat() on.

Let me try to put this in simpler language. When you run 'git status' on your toplevel repository, old-style submodules runs git status on each of the submodule repositories also: this is because submodules were traditionally fixed; therefore, if you forget to commit some changes in submodules before you make the superproject commit, you might break the build. In new-style submodules, you can prevent this from happening on a link-specific basis.