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Re: Boot poster challenge



On Sun, 2004-11-21 at 16:55 +0100, Arjan van de Ven wrote:
> > Disks are very very seek constrained. You get wonderful performance reading
> > linear data. The moment you read a lot of scattered files or a file with a
> > lot of segments you will get low performance - even more so on laptops than
> > desktops
> 
> yeah we saw that; sorting the list on disk sector shaved 2 seconds off...
> if we want to save more we'll have to fix the on disk layout to be less
> spread out. That's not going to be fun...

To elaborate, Arjan suggested analyzing the distribution of the blocks
and [1] does seem to explain why the throughput was good at start but
declined later.

[1] http://www.klika.si/ziga/bootchart/blocks.png
(the image shows the distribution of the readahead file blocks, with a
log scale filesize radius and random vertical distribution;  only the
first 1/4th of the 34GB device is shown).

-- 
Ziga


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