Messages in this thread |  | | Subject | Re: [RESEND RFC PATCH V3] sched: Improve scalability of select_idle_sibling using SMT balance | From | Steven Sistare <> | Date | Fri, 2 Feb 2018 12:39:20 -0500 |
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On 2/2/2018 12:21 PM, Peter Zijlstra wrote: > 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 keep it simple and accept the possibility of choosing the same candidate more than once.
>> 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.
Righto. Disregard this suggestion.
- Steve
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