From: David Kastrup <dak@gnu.org>
Date: Thu, 13 Feb 2014 08:30:15 GMT
Subject: Re: Make the git codebase thread-safe
Message-ID: <87a9dv8lew.fsf@fencepost.gnu.org>
In-Reply-To: <87ppms87n7.fsf@fencepost.gnu.org>

David Kastrup <dak@gnu.org> writes:

> Again, that's with an SSD and ext4 filesystem on GNU/Linux, and there
> are no improvements in system time (I/O) except for patch 4 of the
> series which helps perhaps 20% or so.
>
> So the benefits of the patch will come into play mostly for big, bad
> files on Windows: other than that, the I/O time is likely to be the
> dominant player anyway.
>
> If you have benchmarked the stuff, for annoying cases expect I/O time
> to go down maybe 10-20%, and user time to drop by a factor of 4.
> Under GNU/Linux, that makes for a significant overall improvement.  On
> Windows, the payback is likely quite less because of the worse I/O
> performance.  Pity.

But of course, you can significantly reduce the relevant file
open/close/search times by running

    git gc --aggressive

While this does not actually help with performance in GNU/Linux (though
with file space), dealing with few but compressed files under Windows is
likely a reasonably big win since the uncompression happens in user
space and cannot be bungled by Microsoft (apart from bad memory
management strategies).

-- 
David Kastrup