Messages in this thread |  | | Date | Fri, 2 Feb 2018 18:21:53 +0100 | From | Peter Zijlstra <> | Subject | Re: [RESEND RFC PATCH V3] sched: Improve scalability of select_idle_sibling using SMT balance |
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On Fri, Feb 02, 2018 at 11:53:40AM -0500, Steven Sistare wrote: > It might be interesting to add a tunable for the number of random choices to > make, and clamp it at the max nr computed from avg_cost in select_idle_cpu.
This needs a fairly complicated PRNG for it would need to visit each possible CPU once before looping. A LFSR does that, but requires 2^n-1 elements and we have topology masks that don't match that.. The trivial example is something with 6 cores.
> Or, choose a random starting point and then search for nr sequential > candidates; possibly limited by a tunable.
And this is basically what we already do. Except with the task-cpu instead of a per-cpu rotor.
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