From: Junio C Hamano <gitster@pobox.com>
Date: Sat, 08 Dec 2007 22:18:52 GMT
Subject: Re: Something is broken in repack
Message-ID: <7vodd0vnhv.fsf@gitster.siamese.dyndns.org>
In-Reply-To: <alpine.LFD.0.99999.0712072032410.555@xanadu.home>

Nicolas Pitre <nico@cam.org> writes:

> On Fri, 7 Dec 2007, Jon Smirl wrote:
>
>> Starting with a 2GB pack of the same data my process size only grew to
>> 3GB with 2GB of mmaps.
>
> Which is quite reasonable, even if the same issue might still be there.
>
> So the problem seems to be related to the pack access code and not the 
> repack code.  And it must have something to do with the number of deltas 
> being replayed.  And because the repack is attempting delta compression 
> roughly from newest to oldest, and because old objects are typically in 
> a deeper delta chain, then this might explain the logarithmic slowdown.
>
> So something must be wrong with the delta cache in sha1_file.c somehow.

I was reaching the same conclusion but haven't managed to spot anything
blatantly wrong in that area.  Will need to dig more.