linux-kernel - Re: [PATCH v3 3/8] sched/topology: Switch to assigning "sd->shared" from s

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Message-ID: <7b0eb351-741b-428a-9bb3-ab0b8a0c81e2@amd.com>
Date: Thu, 22 Jan 2026 14:06:44 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Shrikanth Hegde <sshegde@...ux.ibm.com>
CC: Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt
	<rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman
	<mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>, Chen Yu
	<yu.c.chen@...el.com>, "Gautham R. Shenoy" <gautham.shenoy@....com>, "Ingo
 Molnar" <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Juri Lelli
	<juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/8] sched/topology: Switch to assigning "sd->shared"
 from s_data

Hello Shrikanth,

On 1/22/2026 1:42 PM, Shrikanth Hegde wrote:
>> @@ -2709,6 +2720,9 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
>>           if (!cpumask_test_cpu(i, cpu_map))
>>               continue;
>>   +        if (atomic_read(&(*per_cpu_ptr(d.sds, i))->ref))
>> +            *per_cpu_ptr(d.sds, i) = NULL;
>> +
> 
> Can we do this claim_allocations only?

I didn't do it there since we didn't have reference to the "s_data"
inside claim_allocations().

If I remember this right, only init_sched_groups_capacity() has the
requirement to traverse the CPUs in reverse to do
update_group_capacity() when we hit the first CPU in the group.
It doesn't modify the "->ref" of any allocations.

I can put the claim_allocations() bits the previous loop and pass the
CPU and the s_data reference so it can free both "d.sds" and all the
"d.sd" bits in one place and retain this reverse loop for
init_sched_groups_capacity(). Does that sound better?

> sdt_alloc and free is complicated already.
> 
>>           for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
>>               claim_allocations(i, sd);
>>               init_sched_groups_capacity(i, sd);
> 

-- 
Thanks and Regards,
Prateek