From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jonathan Nieder <jrnieder@gmail.com>
Subject: Re: git gc --aggressive led to about 40 times slower "git log --raw"
Date: Tue, 18 Feb 2014 07:59:22 -0800
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Cc: Duy Nguyen <pclouds@gmail.com>,
	Christian Jaeger <chrjae@gmail.com>,
	Git Mailing List <git@vger.kernel.org>
To: David Kastrup <dak@gnu.org>
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David Kastrup wrote:
> Duy Nguyen <pclouds@gmail.com> writes:

>> Likely because --aggressive passes --depth=250 to pack-objects. Long
>> delta chains could reduce pack size and increase I/O as well as zlib
>> processing signficantly.
[...]
> Compression should reduce rather than increase the total amount of
> reads.

--depth=250 means to allow chains of "To get this object, first
inflate this object, then apply this delta" of length 250.

That's absurdly long, and doesn't even help compression much in
practice (many short chains referring to the same objects tends to
work fine).  We probably shouldn't make --aggressive do that.
Something like --depth=10 would make more sense.

Hoping that clarifies,
Jonathan