Re: Delta compression not so effective

From: Martin Langhoff <martin.langhoff@gmail.com>
Date: Mar 1, 2017, 21:08 UTC
Message-ID: <CACPiFCKG7K4jGLHRBA5VrdhLwjqj6KPWS2NYtHjmSdfcRhm+2A@mail.gmail.com>
In-Reply-To: <CA+55aFx7QFqrHw4e72vOdM5z0rw1CCkL2-UX8ej5CLSBWjLNLA@mail.gmail.com>

On Wed, Mar 1, 2017 at 1:30 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote:

> For example, the sorting code thinks that objects with the same name
> across the history are good sources of deltas.

Marius has indicated he is working with jar files. IME jar and war files, which are zipfiles containing Java bytecode, range from not delta-ing in a useful fashion, to pretty good deltas.

Depending on the build process (hi Maven!) there can be enough variance in the build metadata to throw all the compression machinery off.

On a simple Maven-driven project I have at hand, two .war files compiled from the same codebase compressed really well in git. I've also seen projects where storage space is ~101% of the "uncompressed" size.

my 2c,

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