Re: [PATCH] ARM64: Enable multi-core scheduler support by default
From: Dietmar Eggemann
Date: Fri Oct 30 2015 - 08:29:10 EST
On 10/29/2015 05:19 PM, Catalin Marinas wrote:
On Mon, Oct 19, 2015 at 05:55:49PM +0100, Dietmar Eggemann wrote:
Make sure that the task scheduler domain hierarchy is set-up correctly
on systems with single or multi-cluster topology.
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
arch/arm64/configs/defconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
index 34d71dd86781..dc70d715bc38 100644
@@ -51,6 +51,7 @@ CONFIG_PCI=y
Question: does enabling this option have any (positive) effect on the
vanilla kernel or it requires additional patches like EAS?
It improves the task scheduler decisions on multi-cluster systems. You
have to iterate over all cpu's less frequently when gathering the sched
group statistics e.g. during CFS load-balancing.
You essentially replace a flat (all cpus) with an hierarchical approach
(lowest level: sched group eq. cpu, next level: sched group eq. cluster)
and do CFS load balancing frequently between two cpu's of the same
cluster (lowest level) and less frequently between two cpus from
Not sure that I would see an effect on the performance score on a JUNO
board when running hackbench. Could give it a try ... Probably easier to
spot on a machine with >32 logical cpus.
EAS has to work with both approaches although we do all our tests with
CONFIG_SCHED_MC=y. EAS operates on sched groups so the actual structure
of the sched domain hierarchy is hidden. (at least in theory).
For me CONFIG_SCHED_MC=y is something I would expect when I evaluate the
task scheduler on a multi-cluster system.
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