[ ... ] > * Most revealingly, when I used values of read ahead which > were powers of 10, the numbers of block/s reported by > 'vmstat 1' was also a multiple of that power of 10. Most disturbingly, this seems to indicate that not only the Linux block IO subsystems issues IO operations in multiples of the read-ahead size, but does so at a fixed number of times per second that is a multiple of 10. Which leads me to suspect that the queueing of IO requests on the driver's queue, or even the issuing of requests from the driver to the device, may end up being driven by the clock tick interrupt frequency, not the device interrupt frequency. Eventually in my copious free time :-) I shall put in a few traces to see what is the timewise flow of read requests... [ ... ] -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
