Ron Mayer wrote:
Short summary:
* Papers studying priority inversion issues with
databases including PosgreSQL and realistic workloads
conclude setpriority() helps even in the presence of
priority inversion issues for TCP-C and TCP-W like
workloads.
* Avoiding priority inversion with priority inheritance
will further help some workloads (TCP-C) more than
others (TCP-W) but even without such schedulers
priority inversion does not cause as much harm
as the benefit you get from indirectly scheduling
I/O through setpriority() in any paper I've seen.
Andreas Kostyrka wrote:
* Carlos H. Reimer <carlos.reimer@xxxxxxxxxxxxx> [061128 20:02]:
Will the setpriority() system call affect i/o queue too?
Nope, and in fact the article shows the way not to do it.
Actually *YES* setpriority() does have an indirect effect
on the I/O queue.
While I was at Greenplum a related point was made to me:
For a TPC-H/BI type workload on a well configured box the IO subsystem
can be fast enough so that CPU is the bottleneck for much of the time -
so being able to use setpriority() as a resource controller makes sense.
Also, with such a workload being mainly SELECT type queries, the dangers
connected with priority inversion are considerably reduced.
Cheers
Mark
