On Fri, Oct 30, 2015 at 12:29:00PM +0000, Dietmar Eggemann wrote: > 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.eggem...@arm.com> > >>--- > >> 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 > >>--- a/arch/arm64/configs/defconfig > >>+++ b/arch/arm64/configs/defconfig > >>@@ -51,6 +51,7 @@ CONFIG_PCI=y > >> CONFIG_PCI_MSI=y > >> CONFIG_PCI_XGENE=y > >> CONFIG_SMP=y > >>+CONFIG_SCHED_MC=y > >> CONFIG_PREEMPT=y > >> CONFIG_KSM=y > >> CONFIG_TRANSPARENT_HUGEPAGE=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 different cluster. > > 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.
I did some tests on Juno last week with and without this option and I haven't noticed any difference. Anyway, thanks for the explanation. Patch applied. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
