Re: git gc --aggressive led to about 40 times slower "git log --raw"

From: Duy Nguyen <pclouds@gmail.com>
Date: Feb 19, 2014, 00:33 UTC
Message-ID: <CACsJy8C+wGd9WxnsML6-_G_S5GtN2pCPf09kcFtBVu-SDfP8YA@mail.gmail.com>
In-Reply-To: <xmqq4n3warni.fsf@gitster.dls.corp.google.com>

On Wed, Feb 19, 2014 at 7:10 AM, Junio C Hamano <gitster@pobox.com> wrote:

Show 8 quoted lines

> Duy Nguyen <pclouds@gmail.com> writes:
>
>> Lower depth than default (50) does not sound "aggressive" to me, at
>> least from disk space utilization. I agree it should be configurable
>> though.
>
> Do you mean you want to keep "--aggressive" to mean "too aggressive
> in resulting size, to the point that it is not useful to anybody"?

git-gc.txt is pretty vague about this --aggressive. I assume we would want both, better disk utilization and performance. But if it produces a tiny pack that takes forever to access, then it's definitely bad aggression.

> Shallow and wide will give us, with a large window, the most
> aggressively efficient packfiles that are useful, and we would
> rather want to fix it to be usable, I would think.

fwiw this is the thread that added --depth=250

http://thread.gmane.org/gmane.comp.gcc.devel/94565/focus=94626

yes, if reducing depth leads to better performance and does not use much disk in general case, then of course we should do it. "General case" may be hard to define though. It'd be best if we have some sort of heuristics to try out different combinations on a specific repo and return the "best" combination of parameters. It could even take longer time, but once we have good parameters, they should remain good for a long time, I think.

-- 
Duy