From: Ingo Molnar <mingo@elte.hu>
Date: Thu, 31 Jul 2008 21:11:41 GMT
Subject: Re: q: git-fetch a tad slow?
Message-ID: <20080731211141.GA1159@elte.hu>
In-Reply-To: <20080731210307.GF25138@elte.hu>


* Ingo Molnar <mingo@elte.hu> wrote:

> > for strictly local fetch.  If your SSH overhead is ~300 ms this is 
> > only a ~700 ms real time for `git fetch origin`, not 5100 ms.
> > 
> > Is your git-fetch a shell script?  Or a compiled binary?  The port 
> > into C made it go _much_ faster, even though it is still a naive 
> > O(N^2) matching algorithm.  Yea, we still should fix that, but I 
> > think an upgrade to 1.5.4 or later would make the client side 
> > improve consideribly.
> 
> ah, it is a shell script indeed! I'll upgrade to latest.

on another box, with 1.5.4, i have:

 dione:~/tip> time git fetch origin

 real    0m0.481s
 user    0m0.136s
 sys     0m0.060s

 dione:~/tip> time ./tip-fetch
 b714d1a257cca93ba6422ca3276ac80a2cde2b59
 b714d1a257cca93ba6422ca3276ac80a2cde2b59

 real    0m0.273s
 user    0m0.012s
 sys     0m0.020s

that's a 2.66 GHz core2 quad, i.e. a pretty fast box too. As you can see 
most time spent in the tip-fetch case was waiting for the network. So 
there's about 200 msecs of extra CPU cost on the local side. On a CPU 
1-2 generations older that could be up to 1000 msecs or more.

In any case, performance has improved significantly with the C version! 
(I'll still use tip-fetch to squeeze out the last bit of performance, 
but it's quite comparable now.)

Sorry that i didnt notice that titan had 1.5.2 - i almost never notice 
it when i switch between stable git versions. (you guys are doing a 
really good job on compatibility)

	Ingo