Messages in this thread | | | Date | Wed, 31 Oct 2018 20:14:59 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 07/10] sched/fair: Provide can_migrate_task_llc |
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On Mon, Oct 29, 2018 at 07:34:50PM +0000, Valentin Schneider wrote: > On a sidenote, I find it a bit odd that the exec_start threshold depends on > sysctl_sched_migration_cost, which to me is more about idle_balance() cost > than "how long does it take for a previously run task to go cache cold".
A long long (think 2.6.20 long ago) there was code that did boot-time measurement of the various cache topology costs and that threshold was related to that.
That code got killed because of boot to boot variance and dubious benefits.
The migration cost is what it was replaced with as a single measure.
migration cost was then later abused in the newidle balance because it was over eager. Ideally we'd get rid of it there, because we've now got that much more elaborate accounting, but Rohit tried and found some regression because of that.
Maybe we should remove it from newidle anyway.
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