Kernel Space: Toward Better Direct I/O Scalability

“Linux enthusiasts like to point out just how scalable the
system is; Linux runs on everything from pocket-size devices to
supercomputers with several thousand processors. What they talk
about a little bit less is that, at the high end, the true
scalability of the system is limited by the sort of workload which
is run. CPU-intensive scientific computing tasks can make good use
of very large systems, but database-heavy workloads do not scale
nearly as well. There is a lot of interest in making big database
systems work better, but it has been a challenging task. Nick
Piggin appears to have come up with a logical next step in that
direction, though, with a relatively straightforward set of core
memory management changes.

“For some time, Linux has supported direct I/O from user