On-demand readahead

Posted May 24, 2007 15:08 UTC (Thu) by kleptog (subscriber, #1183)
Parent article: On-demand readahead

I'm not surprised MySQL get the benefits. Databases tend to do a lot of almost-but-not-quite sequential reads. There have been reports of people getting substandard performance on postgres because they run afoul of some assumption the kernel is making with respect to readahead. Increasing the readahead buffer tends to help, but it'd be better is the system was slightly smarter.

Given the current costs of seeking, it's really better to read in 10x times the amount of data, even if you're almost sure you're not going to need it. The cost of coming back later is very very high.