* Nick Piggin <[EMAIL PROTECTED]> wrote:
> During periodic load balancing, don't hold this runqueue's lock while
> scanning remote runqueues, which can take a non trivial amount of time
> especially on very large systems.
>
> Holding the runqueue lock will only help to stabalise ->nr_running,
s/stabalise/stabilise/
> however this isn't doesn't do much to help because tasks being woken
s/isn't //
> will simply get held up on the runqueue lock, so ->nr_running would
> not provide a really accurate picture of runqueue load in that case
> anyway.
>
> What's more, ->nr_running (and possibly the cpu_load averages) of
> remote runqueues won't be stable anyway, so load balancing is always
> an inexact operation.
>
> Signed-off-by: Nick Piggin <[EMAIL PROTECTED]>
btw., holding the runqueue lock during the initial scanning portion of
load-balancing is one of the top PREEMPT_RT critical paths on SMP. (It's
not bad, but it's one of the factors that makes SMP latencies higher.)
Acked-by: Ingo Molnar <[EMAIL PROTECTED]>
Ingo
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