Re: [PATCH 3/5] combine-diff: handle binary files as binary

[Junio C Hamano <gitster@pobox.com>]

Jeff King <peff@peff.net> writes:

>   git log -p --cc --merges origin/master
>
> on git.git using both v1.7.5.3 and the jk/combine-diff-binary-etc
> branch. And it turns out that the extra loads really don't make a
> difference in practice. My best-of-5 for the two cases were:

I am not surprised. git.git is small enough and developer machines these
days are beefy enough so that most of the data from the disk are sitting
in the buffer cache, and if you are well packed and Linus's law "a file
always grows" holds true, it is likely that you are also benefiting from
the delta-base cache, as the history traversal of the command goes newer
to older.

>   $ time git.v1.7.5.3 log -p --cc --merges origin/master >/dev/null
>   real    0m59.518s
>   user    0m58.672s
>   sys     0m0.688s

Comparing that with the run time of the same log without patch generation
would roughly give the cost of "all text combined" diff. I suspect more
than 90% of the time goes to running the textual diff algorithm.

I guess you are hinting that we should optimize that part before worrying
about the wastage of reading these blobs always twice.