2015-07-24 Nicolas Barbier <nicolas.barbier@gmail.com>:
> Especially useful would be to know whether interleaving a small number
> of TID ordered streams (as would probably be generated by parallel
> scans/processing) would result in an ordering that performs
> significantly worse or not. I assume (but cannot prove) that in this
> case the OS will understand the read pattern as being multiple streams
> and prefetching will work correctly.
OTOH, that is probably only true when there are a large number of
duplicate keys. Otherwise the order within each (small) group will
appear random, which may or may not result in a significant
performance drop. This probably also depends on whether fadvise (or
friends) are used.
Nicolas
--
A. Because it breaks the logical sequence of discussion.
Q. Why is top posting bad?