linux-kernel - Re: [PATCH v7 0/8] sched/fair: Get rid of sched_domains_curr

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Message-ID: <8eadbf18-f930-41ab-bd0c-344f95324687@linux.ibm.com>
Date: Mon, 1 Sep 2025 22:36:39 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Valentin Schneider <vschneid@...hat.com>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
        Mel Gorman <mgorman@...e.de>, thomas.weissschuh@...utronix.de,
        Li Chen <chenl311@...natelecom.cn>, Bibo Mao <maobibo@...ngson.cn>,
        Mete Durlu <meted@...ux.ibm.com>,
        Tobias Huschle <huschle@...ux.ibm.com>,
        Easwar Hariharan <easwar.hariharan@...ux.microsoft.com>,
        Guo Weikang <guoweikang.kernel@...il.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Brian Gerst <brgerst@...il.com>,
        Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>,
        Swapnil Sapkal <swapnil.sapkal@....com>,
        "Yury Norov [NVIDIA]" <yury.norov@...il.com>,
        Sudeep Holla <sudeep.holla@....com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Andrea Righi <arighi@...dia.com>,
        Yicong Yang <yangyicong@...ilicon.com>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org
Subject: Re: [PATCH v7 0/8] sched/fair: Get rid of sched_domains_curr_level
 hack for tl->cpumask()



On 9/1/25 2:28 PM, Peter Zijlstra wrote:
> On Fri, Aug 29, 2025 at 02:23:06PM +0530, Shrikanth Hegde wrote:
> 
>> I was looking at: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/log/?h=sched/core
>>
>> Current code doesn't allow one to enable/disable SCHED_MC on ppc since it is set always in kconfig.
>> Used the below patch:
>>
>> I think since the config is there, it would be good to provide a option to disable. no?
> 
> So current PPC code has this MC thing unconditional. I've been
> preserving that behaviour. If PPC maintainers feel they want this
> selectable, I'm happy to include something like the below, but as a
> separate patch with a separate changelog that states this explicit
> choice.
> 

Fair enough. Will send it as separate patch.

>> ---
>>
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index fc0d1c19f5a1..da5b2f8d3686 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -170,9 +170,8 @@ config PPC
>>   	select ARCH_STACKWALK
>>   	select ARCH_SUPPORTS_ATOMIC_RMW
>>   	select ARCH_SUPPORTS_DEBUG_PAGEALLOC	if PPC_BOOK3S || PPC_8xx
>> -	select ARCH_SUPPORTS_SCHED_SMT		if PPC64 && SMP
>>   	select ARCH_SUPPORTS_SCHED_MC		if PPC64 && SMP
>> -	select SCHED_MC				if ARCH_SUPPORTS_SCHED_MC
>> +	select ARCH_SUPPORTS_SCHED_SMT		if PPC64 && SMP
>>   	select ARCH_USE_BUILTIN_BSWAP
>>   	select ARCH_USE_CMPXCHG_LOCKREF		if PPC64
>>   	select ARCH_USE_MEMTEST
>> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
>> index 68edb66c2964..458ec5bd859e 100644
>> --- a/arch/powerpc/kernel/smp.c
>> +++ b/arch/powerpc/kernel/smp.c
>> @@ -1706,10 +1706,12 @@ static void __init build_sched_topology(void)
>>   			SDTL_INIT(tl_cache_mask, powerpc_shared_cache_flags, CACHE);
>>   	}
>> +#ifdef CONFIG_SCHED_MC
>>   	if (has_coregroup_support()) {
>>   		powerpc_topology[i++] =
>>   			SDTL_INIT(tl_mc_mask, powerpc_shared_proc_flags, MC);
>>   	}
>> +#endif
>>   	powerpc_topology[i++] = SDTL_INIT(tl_pkg_mask, powerpc_shared_proc_flags, PKG);
>>


If possible for below two, please consider tags.

https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?h=sched/core&id=496d4cc3d478a662f90cce3a3e3be4af56f78a02
https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?h=sched/core&id=a912f3e2c6d91f7ea7b294c02796b59af4f50078

Reviewed-by: Shrikanth Hegde <sshegde@...ux.ibm.com>

for powerpc bits:
Tested-by: Shrikanth Hegde <sshegde@...ux.ibm.com>