Re: [PATCH 4/4] sched/fair: Proportional newidle balance

Dietmar Eggemann
2025-11-10T13:55:43Z

On 07.11.25 17:06, Peter Zijlstra wrote:
> Add a randomized algorithm that runs newidle balancing proportional to
> its success rate.
>
> This improves schbench significantly:
>
> 6.18-rc4: 2.22 Mrps/s
> 6.18-rc4+revert: 2.04 Mrps/s
> 6.18-rc4+revert+random: 2.18 Mrps/S
>
> Conversely, per Adam Li this affects SpecJBB slightly, reducing it by 1%:
>
> 6.17: -6%
> 6.17+revert: 0%
> 6.17+revert+random: -1%
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Results with OLTP 'hammerdb - mysqld' on Arm64 VMs

NOPM P50 latency

6.18-rc4 baseline baseline

6.18-rc4+revert-155213a2aed4 +13% -8.8%

6.18-rc4+patchset +11% -8.2%

6.18-rc4+patchset+NO_NI_RANDOM +13% -8.6%

Pretty consistent with the results on the previous version. Although I
hadn't tested NI_TARGET+NI_RANDOM back then.

http://lkml.kernel.org/r/f6379aa6-459d-4205-96ea-9848e55d7f9c@arm.com

In case (pure wakeup) schbench configs are the only workloads profiting
from NI_RANDOM, make NO_NI_RANDOM the default?

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> …