Re: [PATCH v2 04/10] powerpc/smp: Enable small core scheduling sooner

[Gautham R Shenoy <ego@linux.vnet.ibm.com>]

Hello Srikar,

On Tue, Jul 21, 2020 at 05:08:08PM +0530, Srikar Dronamraju wrote:
> Enable small core scheduling as soon as we detect that we are in a
> system that supports thread group. Doing so would avoid a redundant
> check.

The patch looks good to me. However, I think the commit message still
reflect the v1 code where we were moving the functionality from
smp_cpus_done() to init_big_cores().

In this we are moving it to a helper function to collate all fixups to
topology.

> 
> Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
> Cc: LKML <linux-kernel@vger.kernel.org>
> Cc: Michael Ellerman <michaele@au1.ibm.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Valentin Schneider <valentin.schneider@arm.com>
> Cc: Nick Piggin <npiggin@au1.ibm.com>
> Cc: Oliver OHalloran <oliveroh@au1.ibm.com>
> Cc: Nathan Lynch <nathanl@linux.ibm.com>
> Cc: Michael Neuling <mikey@linux.ibm.com>
> Cc: Anton Blanchard <anton@au1.ibm.com>
> Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
> Cc: Vaidyanathan Srinivasan <svaidy@linux.ibm.com>
> Cc: Jordan Niethe <jniethe5@gmail.com>
> Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> ---
> Changelog v1 -> v2:
> powerpc/smp: Enable small core scheduling sooner
> 	Restored the previous info msg (Jordan)
> 	Moved big core topology fixup to fixup_topology (Gautham)
> 
>  arch/powerpc/kernel/smp.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 1ce95da00cb6..72f16dc0cb26 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -1370,6 +1370,16 @@ int setup_profiling_timer(unsigned int multiplier)
>  	return 0;
>  }
> 
> +static void fixup_topology(void)
> +{
> +#ifdef CONFIG_SCHED_SMT
> +	if (has_big_cores) {
> +		pr_info("Big cores detected but using small core scheduling\n");
> +		powerpc_topology[0].mask = smallcore_smt_mask;
> +	}
> +#endif
> +}
> +
>  void __init smp_cpus_done(unsigned int max_cpus)
>  {
>  	/*
> @@ -1383,12 +1393,7 @@ void __init smp_cpus_done(unsigned int max_cpus)
> 
>  	dump_numa_cpu_topology();
> 
> -#ifdef CONFIG_SCHED_SMT
> -	if (has_big_cores) {
> -		pr_info("Big cores detected but using small core scheduling\n");
> -		powerpc_topology[0].mask = smallcore_smt_mask;
> -	}
> -#endif
> +	fixup_topology();
>  	set_sched_topology(powerpc_topology);
>  }
> 
> -- 
> 2.17.1
>