Re: pack operation is thrashing my server

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Aug 15, 2008, 00:06 UTC
Message-ID: <alpine.LFD.1.10.0808141656120.3324@nehalem.linux-foundation.org>
In-Reply-To: <20080814233958.GA31225@atjola.homenet>

On Fri, 15 Aug 2008, Björn Steinbrink wrote:

Show 7 quoted lines

> 
> Since you mention the delta cache, uau (no idea about his real name) on
> #git was talking about some delta cache optimizations lately, although
> he was dealing with "git log -S", maybe it affects rev-list in a similar
> way. Unfortunately, I can't seem to find any code for that, just a
> description of what he did and some numbers on the results in the IRC
> logs.

Yes, interesting.

The delta cache was really a huge hack that just turned out rather successful. It's been hacked on further since (to do some half-way reasonable replacement with _another_ hack by adding an LRU on top of it), but it really is very hacky indeed.

The "hash" we use for looking things up is also pretty much a joke, and it has no overflow capability, it just replaces the old entry with a new one.

I wonder how hard it would be to replace the whole table thing with our generic hash.c hash thing. I'll take a look.

			Linus