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
