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