Linux elevators (Re: BFQ: simple elevator)

[Arlie Stephens]

The ongoing thread reminds me of a simple question I've had since I
first read about linux' mutiple I/O schedulers. Why is the choice of
I/O scheduler global to the whole kernel, rather than per-device or
similar? 

Consider a system with both traditional rotating disks and SSDs - not
at all far fetched. An appropriate I/O scheduling algorithm for
rotating disks is likely to do a lot of work that's useless for
SSDs. Why require that the same algorithms be used for both? 

--
Arlie

(Arlie Stephens					arlie at worldash.org)