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SubjectRe: [PATCH 10/15] sched: Check for sched_mn_power_savings when doing load balancing
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On Thu, 2009-08-20 at 15:41 +0200, Andreas Herrmann wrote:
> The patch adds support for POWERSAVINGS_BALANCE_BASIC for MN domain
> level. Currently POWERSAVINGS_BALANCE_WAKEUP is not used for MN domain.
>
> (I have to admit that so far I don't have the correct understanding
> what's the benefit of POWERSAVINGS_BALANCE_WAKEUP (when an deticated
> wakeup CPU is used) in contrast to POWERSAVINGS_BALANCE_BASIC. I also
> have not found an example that would demonstrate the difference
> between those two powersaving levels.)

blame svaidy for not writing enough comments ;-)

iirc it moves tasks to sched_mv_preferred_wakeup_cpu instead of waking
an idle cpu, this leaves idle cpus idle longer at the cost of creating
overload on other cpus.

> Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
> ---
> kernel/sched.c | 5 +++--
> 1 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched.c b/kernel/sched.c
> index ebcda58..7a0d710 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -4591,7 +4591,8 @@ static int find_new_ilb(int cpu)
> * Have idle load balancer selection from semi-idle packages only
> * when power-aware load balancing is enabled
> */
> - if (!(sched_smt_power_savings || sched_mc_power_savings))
> + if (!(sched_smt_power_savings || sched_mc_power_savings ||
> + sched_mn_power_savings))
> goto out_done;
>
> /*
> @@ -4681,7 +4682,7 @@ int select_nohz_load_balancer(int stop_tick)
> int new_ilb;
>
> if (!(sched_smt_power_savings ||
> - sched_mc_power_savings))
> + sched_mc_power_savings || sched_mn_power_savings))
> return 1;
> /*
> * Check to see if there is a more power-efficient


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