From: Junio C Hamano <gitster@pobox.com>
Date: Thu, 10 Jul 2008 15:34:45 GMT
Subject: Re: THREADED_DELTA_SEARCH
Message-ID: <7vy749pxbe.fsf@gitster.siamese.dyndns.org>
In-Reply-To: <20080710075327.GD24819@artemis.madism.org>

Pierre Habouzit <madcoder@debian.org> writes:

>   I'm using it in production for quite a long time now, and I wonder if
> there is any specific reason why it's not default. Debian activated it
> by default too a couple of weeks ago, which means that it's in
> production on quite a large scale, and there are no issues reported
> either. Would a patch making it default be accepted ? It's quite handy
> given that SMP machines are really pervasive nowadays…

There were two issues, IIRC.

 (1) resulting pack could be suboptimal, due to delta-chain getting cut
     betweeen the worker thread boundary.

 (2) exploding memory use, suspected to be due to malloc pool
     fragmentation under multithreading.

The former was only an issue with early iterations of the code and the
current code has much improved behaviour on this point, but I do not
recall the latter issue has been addressed.