Re: How git affects kernel.org performance

From: Fengguang Wu <fengguang.wu@gmail.com>
Date: Jan 10, 2007, 01:57 UTC
Message-ID: <368394226.19365@ustc.edu.cn>
In-Reply-To: <Pine.LNX.4.64.0701090821550.3661@woody.osdl.org>

On Tue, Jan 09, 2007 at 08:23:32AM -0800, Linus Torvalds wrote:

Show 13 quoted lines

>
>
> On Tue, 9 Jan 2007, Fengguang Wu wrote:
> > >
> > > The fastest and probably most important thing to add is some readahead
> > > smarts to directories --- both to the htree and non-htree cases.  If
> >
> > Here's is a quick hack to practice the directory readahead idea.
> > Comments are welcome, it's a freshman's work :)
>
> Well, I'd probably have done it differently, but more important is whether
> this actually makes a difference performance-wise. Have you benchmarked it
> at all?

Yes, a trivial test shows a marginal improvement, on a minimal debian system:

# find / | wc -l 13641

# time find / > /dev/null

real 0m10.000s user 0m0.210s sys 0m4.370s

# time find / > /dev/null

real 0m9.890s user 0m0.160s sys 0m3.270s

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> Doing an
>
> 	echo 3 > /proc/sys/vm/drop_caches
>
> is your friend for testing things like this, to force cold-cache
> behaviour..

Thanks, I'll work out numbers on large/concurrent dir accesses soon.

Regards, Wu