From: Julian Phillips <julian@quantumfyre.co.uk>
Date: Thu, 13 Nov 2008 23:23:38 GMT
Subject: Re: hosting git on a nfs
Message-ID: <alpine.LNX.2.00.0811132317100.3965@reaper.quantumfyre.co.uk>
In-Reply-To: <alpine.LFD.2.00.0811131252040.3468@nehalem.linux-foundation.org>

On Thu, 13 Nov 2008, Linus Torvalds wrote:

> Before:
>
> 	[torvalds@nehalem linux]$ /usr/bin/time git diff > /dev/null
> 	0.03user 0.04system 0:00.07elapsed 100%CPU (0avgtext+0avgdata 0maxresident)k
>
> After:
>
> 	0.02user 0.07system 0:00.04elapsed 243%CPU (0avgtext+0avgdata 0maxresident)k
> 	0inputs+0outputs (0major+2241minor)pagefaults 0swaps
>
> ie it actually did cut elapsed time from 7 hundredths of a second to just
> 4. And the CPU usage went from 100% to 243%. Ooooh. Magic.
>
> But it's still hacky as hell. Who has NFS? Can you do the same thing over
> NFS and test it? I'm not going to set up NFS to test this, and as I
> suspected, on a local disk, the cold-cache case makes no difference
> what-so-ever, because whatever seek optimizations can be done are still
> totally irrelevant.

The timings seem to vary quite a bit (not really a surprise with a network 
involved ;), but the patch definately makes things faster:

master:

jp3@kaos: linux-2.6(master)>/usr/bin/time ~/bin/git diff > /dev/null
0.01user 0.19system 0:02.50elapsed 8%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+1766minor)pagefaults 0swaps

master + patch:

jp3@kaos: linux-2.6(master)>/usr/bin/time ~/bin/git diff > /dev/null
0.02user 0.88system 0:00.96elapsed 93%CPU (0avgtext+0avgdata 
0maxresident)k
0inputs+0outputs (0major+1783minor)pagefaults 0swaps

seems to be approximately twice as fast?

-- 
Julian

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