linux-kernel - Re: [PATCH v2 6/6 RFT] sched/fair: change sched asym checking condition

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Date: Thu, 1 Feb 2024 20:49:05 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: kuiliang Shi <seakeel@...il.com>, alexs@...nel.org
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>, linux-kernel@...r.kernel.org,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Subject: Re: [PATCH v2 6/6 RFT] sched/fair: change sched asym checking
 condition



On 2/1/24 5:10 PM, kuiliang Shi wrote:
> 
> 
> On 2/1/24 9:10 AM, Ricardo Neri wrote:
>> On Tue, Jan 30, 2024 at 09:17:08PM +0800, alexs@...nel.org wrote:
>>> From: Alex Shi <alexs@...nel.org>
>>>
>>> Asym only used on SMT sd, or core sd with ITMT and core idled.
>>> !sched_smt_active isn't necessary.
>>
>> sched_smt_active() is implemented as a static key. Thus, if SMT is not
>> enabled, we can quickly return without having to check the rest of the
>> conditions, as we should.
> 
> Hi Ricardo,
> 
> Thanks a lot for comments! I will drop this patch in this series.
> 
> But forgive my stupidity, asym feature is possible when SMT enabled instead of SMT disable. Why no SMT is a condition for asm feature? For this asym feature, I only see the SMT and MC domain use this, correct me if I'm wrong. 
> 

on power7 ASYM_PACKING is used to pack at SMT level. 

On x86, ITMT topology uses ASYM_PACKING to do load balancing instead of using different cpu capacities.

Its possible to have it in PKG(earlier referred as DIE) as well. 
In powerpc recently we did that for shared processor LPAR's. So asym feature is in PKG as well. 

>>
>>>