Messages in this thread | | | Date | Sat, 31 Dec 2005 17:31:35 +0100 | From | Paolo Ornati <> | Subject | Re: [SCHED] wrong priority calc - SIMPLE test case |
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On Sun, 01 Jan 2006 00:44:10 +1100 Peter Williams <pwil3058@bigpond.net.au> 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.
-- Paolo Ornati Linux 2.6.15-rc7-lial on x86_64 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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