Re: About git-bisect (was: Linux 2.6.28-rc7)

From: Linus Torvalds
Date: Tue Dec 02 2008 - 12:06:00 EST

On Tue, 2 Dec 2008, Sam Ravnborg wrote:
> You do not need to do a "make clean" between each build, so if none
> of the core files are touched you should be much faster.

Not for big ranges, sadly.

Because "git bisect" tends to jump around wildly, it's very rare to not
have to rebuild the whole tree. Only at the very last few bisection events
(when it's been narrowed down to just a few tens of commits) will you
generally see your compiles speed up.

That said, the _best_ way to speed up your compile (whether bisecting or
not) is to simply only compile the drivers and modules you actually need.
It takes me 16 seconds to compile my kernel (if it's all cached), and
that's largely because I do _not_ compile one of the crazy distro kernels
with thousands of totally irrelevant modules for my setup.

A good config file will not just result in a smaller kernel, it will often
cut down your kernel compile times by a factor of ten or even more.

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