Re: A potential approach to making tests faster on Windows

[Eric Sunshine <sunshine@sunshineco.com>]

On Tue, Apr 3, 2018 at 5:49 AM, Johannes Schindelin
<Johannes.Schindelin@gmx.de> wrote:
> My main evidence that shell scripts on macOS are slower than on Linux was
> the difference of the improvement incurred by moving more things from
> git-rebase--interactive.sh into sequencer.c: Linux saw an improvement only
> of about 3x, while macOS saw an improvement of 4x, IIRC. If I don't
> remember the absolute numbers correctly, at least I vividly remember the
> qualitative difference: It was noticeable.

MacOS is _slow_, much, much slower than, say, Linux.

Several years ago, when I had this machine configured for multi-boot,
I ran MacOS and Linux on bare metal. Back then, using ram disk for the
"trash" directories, and disabling Spotlight indexing on MacOS to
avoid it eating CPU and causing I/O contention, the Git test suite
would run to completion on Linux in slightly over 1 minute. On MacOS,
it would take over 10 minutes; 10 times slower.

These days, the Git test suite takes 15 minutes to run on the same
hardware (with same conditions: ram disk and Spotlight disabled),
which is painfully slow, thus I rarely do it. Unfortunately, I don't
have Linux installed on bare metal anymore, so I can't make a proper
comparison, but I do run Linux in a virtual machine under MacOS and,
even though its running within a virtualized environment, Linux is
still much faster than MacOS, taking 4:25 (slow, but not to the point
of outright pain).

That the test suite runs so much faster on Linux (bare metal or
virtualized) than MacOS on this machine, I have attributed (or
understood as being due) to poor HFS+ filesystem performance. It's
even worse when Spotlight interferes. Presumably, the new, recently
released, Mac filesystem has improved performance, but it's restricted
to SSD's, whereas this machine has a physical drive, thus I can't test
it.