On Sun, 01 Jan 2006 00:44:10 +1100
Peter Williams <pwil3058@xxxxxxxxxxxxxx> wrote:
OK. This probably means that the parameters that control the mechanism need tweaking.
There should be a file /sys/cpusched/attrs/unacceptable_ia_latency which contains the latency (in nanoseconds) that the scheduler considers unacceptable for interactive programs. Try changing that value and see if things improve? Making it smaller should help but if you make it too small all the interactive tasks will end up with the same priority and this could cause them to get in each other's way.
I've tried different values and sometimes I've got a good feeling BUT
the behaviour is too strange to say something.
Sometimes I get what I want (dd priority ~17 and CPU eaters prio
25), sometimes I get a total disaster (dd priority 17 and CPU eaters
prio 15/16) and sometimes I get something like DD prio 22 and CPU
eaters 23/24.
All this is not well related to "unacceptable_ia_latency" values.
What I think is that the priority calculation in ingosched and other
schedulers is in general too weak, while in other schedulers is rock
solid (read: nicksched).
Maybe is just that the smarter a scheduler want to be, the more fragile
it will be.