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Date: Fri, 17 Jul 2020 11:18:21 +0530
From: Gautham R Shenoy <ego@linux.vnet.ibm.com>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Subject: Re: [PATCH 04/11] powerpc/smp: Enable small core scheduling sooner
Message-ID: <20200717054821.GD25851@in.ibm.com>
References: <20200714043624.5648-1-srikar@linux.vnet.ibm.com>
 <20200714043624.5648-5-srikar@linux.vnet.ibm.com>
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Reply-To: ego@linux.vnet.ibm.com
Cc: Nathan Lynch <nathanl@linux.ibm.com>,
 Gautham R Shenoy <ego@linux.vnet.ibm.com>,
 Oliver OHalloran <oliveroh@au1.ibm.com>, Michael Neuling <mikey@linux.ibm.com>,
 Michael Ellerman <michaele@au1.ibm.com>, Anton Blanchard <anton@au1.ibm.com>,
 linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
 Nick Piggin <npiggin@au1.ibm.com>
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 <linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org>

On Tue, Jul 14, 2020 at 10:06:17AM +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.
> 
> Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
> Cc: Michael Ellerman <michaele@au1.ibm.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>
> Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

I don't see a problem with this.

However, since we are now going to be maintaining a single topology
structure, wouldn't it be better to collate all the changes being made
to the mask_functions/flags/names of this structure within a single
function so that it becomes easier to keep track of what all changes
are going into the topology and why are we doing it?


> ---
>  arch/powerpc/kernel/smp.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 24529f6134aa..7d430fc536cc 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -892,6 +892,12 @@ static int init_big_cores(void)
>  	}
> 
>  	has_big_cores = true;
> +
> +#ifdef CONFIG_SCHED_SMT
> +	pr_info("Big cores detected. Using small core scheduling\n");
> +	powerpc_topology[0].mask = smallcore_smt_mask;
> +#endif
> +
>  	return 0;
>  }
> 
> @@ -1383,12 +1389,6 @@ 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
>  	set_sched_topology(powerpc_topology);
>  }
> 
> -- 
> 2.17.1
>