Re: A potential approach to making tests faster on Windows

[Jeff King <peff@peff.net>]

On Tue, Apr 03, 2018 at 06:00:05PM +0200, Johannes Schindelin wrote:

> > But if we're at the point of creating custom C builtins for
> > busybox/dash/etc, you should be able to create a primitive for "read
> > this using buffered stdio, other processes be damned, and return one
> > line at a time".
> 
> Well, you know, I do not think that papering over the root cause will make
> anything better. And the root cause is that we use a test framework
> written in Unix shell.

I'm not entirely convinced of this. My earlier numbers show that we
spend a lot of time actually running Git. But that's not because we're
written in shell, but because the stable interface to Git is running
individual processes.

So we can unit-test wildmatch or similar in a single C program, but I
think we inherently need to run "git init" a lot of times.

Now I think there's reason to doubt some of my numbers. I was counting
exec's, and non-exec forks due to subshells, etc, may be important. So I
claim only that I remain unconvinced that we are certain of the root
cause.

At any rate, I would be happy to see more study into this. If we can
create a measurable speedup for an existing script, that might give us a
blueprint for speeding up the whole suite.

-Peff