Re: [RFC] Patch for isolated scheduler domains

From: Nick Piggin (nickpiggin_at_yahoo.com.au)
Date: 07/23/04

  • Next message: Nick Piggin: "Re: [VM PATCH 2.6.8-rc1] Prevent excessive scanning of lower zone" 
    Date:	Fri, 23 Jul 2004 13:27:24 +1000
To: Ingo Molnar <mingo@elte.hu>

    Ingo Molnar wrote:
    > * Dimitri Sivanich <sivanich@sgi.com> wrote:
    >
    >
    >>I'm interested in implementing something I'll call isolated sched
    >>domains for single cpus (to minimize the latencies involved when doing
    >>things like load balancing on certain select cpus) on IA64.
    >>
    >>Below I've included an initial patch to illustrate what I'd like to
    >>do. I know there's been mention of 'platform specific work' in the
    >>area of sched domains. This patch only addresses IA64, but could be
    >>made generic as well. The code is derived directly from the current
    >>default arch_init_sched_domains code.
    >
    >
    > it looks good to me - and i'd suggest to put it into sched.c. Every
    > architecture benefits from the ability to define isolated CPUs.
    >

    Cool. Have you actually tried running it? With Ingo's correction, it
    should work fine but I don't think anyone has tested this.

    > One minor nit wrt. this line:
    >
    > + cpu_sd->flags &= ~(SD_BALANCE_NEWIDLE | SD_BALANCE_EXEC |
    > + SD_BALANCE_CLONE); /* Probably redundant */
    >
    > i'd suggest to set it to 0. You dont want WAKE_AFFINE nor WAKE_BALANCE
    > to move your tasks out of the isolated domain.
    >
    >
    >>- Assuming boot time configuration is appropriate ('isolcpus=' in my example),
    >> is allowing boot time configuration of only completely isolated cpus
    >> focusing too narrowly on this one concept, or should a boot time
    >> configuration allow for a broader array of configurations, or would other
    >> types of sched domain configurations be addressed separately?
    >
    >
    > i'd prefer to go with this simple solution and wait for actual usage
    > patterns to materialize. If it becomes popular we can define a syscall
    > to configure the domain hierarchy (maybe even the parameters) runtime.
    >

    Seconded.
    -
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